2. Basic

FAQ Home

2.1	What is ASP.NET?

2.2	Why does my ASP.NET file have multiple <form> tag with runat=server?

2.3	How to find out what version of ASP.NET I am using on my machine?

2.4	Is it possible to pass a querystring from an .asp page to aspx page?

2.5	How to comment out ASP.NET Tags?

2.6	What is a ViewState?

2.7	Where can I get the details on Migration of existing projects using various technologies to ASP.NET?

2.8	What is the equivalent of date() and time() in ASP.NET?

2.9	How to prevent a button from validating it's form?

2.10	How to get the IP address of the host accessing my site?

2.11	How to access the Parameters passed in via the URL?

2.12	How to Set Focus to Web Form Controls By Using Client-Side Script?

2.13	How to display a Wait page while a query is running?

2.14	How to implement Form based Authentication in ASP.NET application?

2.15	How to catch the 404 error in my web application and provide more useful information?

2.16	Is there a method similar to Response.Redirect that will send variables to the destination page other than using a query string or the post method?

2.17	What are the differences between HTML versus Server Control?

2.18	How can I change the action of a form through code?

2.19	Is there any control that allows user to select a time from a clock - in other words is there a clock control?

2.20	How to Compare time?

2.21	How To work with TimeSpan Class?

2.22	Where can I get information on Cookies in ASP.NET?

2.23	Does ASP.Net still recognize the global.asa file?

2.24	How should I destroy my objects in ASP.Net?

2.25	Are there resources online with tips on ASP to ASP.Net conversions?

2.26	How do I publish my ASP.NET application to my ISP's web server?

2.27	Why do i get error message "Could not load type" whenever I browse to my ASP.NET web site?

2.28	Will the WebMatrix SqlDataSourceControl work with a MySQL connection?

2.29	Can I combine classic ASP and ASP.NET pages?

2.30	What is the difference between src and Code-Behind?

2.31	How can I get the value of input box with type hidden in code-behind?

2.32	I have created a .NET user control page (.ascx) but I cannot compile and run it.

2.33	What is a .resx file?

2.34	Is it possible to use a style sheet class directly on a control instead of using inline or page-level formatting ?

2.35	Can I recieve both HTML markup for page and code in the ASP.NET web page's source code portion in the Web browser?

2.36	Why can't I put <%@ Page Language="C " %> where at the top of an ASPX file and write my server-side scripts in C ?

2.37	ASP pages that worked pefectly on Windows 2000 Server and IIS 5.0 do not work on Windows 2003 Server with IIS 6.0. ASP.NET pages work fine. Why?

2.38	Why do I get error message "Error creating assembly manifest: Error reading key file 'key.snk' -- The system cannot find the file specified"?

2.39	How to get URL without querystring?

2.40	What is the best way to output only time and not Date?

2.41	Do I have to compile code if I am changing the content of my aspx.cs file?

2.42	How to grab the referring URL?

2.43	My ASP code gives an error "Compiler Error Message: BC30289: Statement cannot appear within a method body. End of method assumed" when changed to .aspx?

2.44	How can I save images ?

2.45	How can I logout when using FormsAuthentication?

2.46	Why do I get a blank page when I use Server.Transfer("page1.htm") to transfer to a different page?

2.47	How to detect the User's culture?

2.48	What is the difference between CurrentCulture property and the CurrentUICulture property?

2.49	Can I read the hard disk serial # of the client computer using ASP.NET?

2.50	What is xxx(src As Object, e As EventArgs)?

2.51	What is the difference between Absolute vs Relative URLs?

2.52	What is the difference between URL and URI?

2.53	How to convert milliseconds into time?

2.54	How to include multiple vb/cs files in the source?

2.55	How to convert a string to Proper Case?

2.56	How can I ensure that application-level variables are not updated by more than one user simultaneously?

2.57	Why do I get the error message "System.InvalidOperationException: It is invalid to show a modal dialog or form when the application is not running in UserInteractive mode. Specify the ServiceNotification or DefaultDesktopOnly style to display a ...."?

2.58	How to validate that a string is a valid date?

2.59	Are namespaces and Class names Case Sensitive?

2.60	How to convert string to a DateTime and compare it with another DateTime?

2.61	How to get the url of page dynamically?

2.62	How to convert user input in dMy format to Mdy?

2.63	When the User is prompted a File Download dialogbox, if the user selects "Save" then the "Save as" dialog box is displayed. Is there any way for me to retrieve the filename and directory path specified by the user on the File Download dialog box?

2.64	How to hide or show Controls in server side code?

2.65	How to check if the user is using a secure or non secure connection?

2.66	Is it possible to write code in many languages in one ASP.NET project?

2.67	What is the difference between Response.Redirect() and Server.Transfer().

2.68	How to get the hostname or IP address of the server?

2.69	What is the meaning of validateRequest=true in .net framework1.1?

2.70	What is the different between <%# %> and <%= %>?

2.71	What permissions do ASP.NET applications posses by default?

2.72	How can I specify the relative path for a file?

2.73	How can I specify the "upload a file" input textbox in a form to be read only so that the user can click on the browse button and pick a file but they cannot type anything into the textbox next to the browse button.

2.74	How to change the Page Title dynamically?

2.75	Why do I get the error message "Object must implement IConvertible". How can I resolve it?

2.76	Why is default.aspx page not opened if i specify http://localhost. I am able to view this page if i hardcode it as http://localhost/default.aspx?

2.77	Can ASP.NET work on an NT server?

2.78	Is it possible to migrate Visual InterDev Design-Time Controls to ASP.NET?

2.79	How to automatically get the latest version of all the asp.net solution items from Source Safe when opening the solution?

2.80	How to convert the datetime into a string for use in the SQL ' statement?

2.81	How to make VS.Net use FlowLayout as the default layout rather than the GridLayout?

2.82	Can I use a DataReader to update/insert/delete a record?

2.83	What is the difference between Server.Transfer and Server.Execute?

2.84	How to create a login screen in ASP.NET?

2.85	How to format a Telphone number in the xxx-xxx-xxxx format?

2.86	Can two different programming languages be mixed in a single ASPX file?

2.87	Can I use custom .NET data types in a Web form?

2.88	How can I have a particular Web page in an ASP.NET application which displays its own error page.

2.1 What is ASP.NET?

ASP.NET is a programming framework built on the common language runtime that can be used on a server to build powerful Web applications.

For more details refer

2.2 Why does my ASP.NET file have multiple <form> tag with runat=server?

This means that ASP.Net is not properly registered with IIS.
.Net framework provides an Administration utility that manages the installation and uninstallation of multiple versions of ASP.NET on a single machine. You can find the file in C:\WINNT\Microsoft.NET\Framework\v**\aspnet_regiis.exe

use the command: aspnet_regiis.exe -u ---> to uninstall current asp.net version.

use the command: aspnet_regiis.exe -i ---> to install current asp.net version.

For Windows Server 2003, you must use aspnet_regiis -i -enable
This is because of the "Web Service Extensions" feature in IIS 6

(if you install VS.NET or the framework without IIS installed, and then go back in and install IIS afterwards, you have to re-register so that ASP.NET 'hooks' into IIS properly."

2.3 How to find out what version of ASP.NET I am using on my machine?

VB.NET

Response.Write(System.Environment.Version.ToString() )

Response.Write(System.Environment.Version.ToString() );

2.4 Is it possible to pass a querystring from an .asp page to aspx page?

Yes you can pass querystring from .asp to ASP.NET page .asp

<%response.redirect "webform1.aspx?id=11"%>

.aspx
VB.NET

Response.Write (Request("id").ToString ())

Response.Write (Request["id"].ToString ());

2.5 How to comment out ASP.NET Tags?

<%--<asp:Label id="Label1" style="Z-INDEX: 101; LEFT: 8px; POSITION: absolute; TOP: 48px" runat="server">Label</asp:Label>--%>

2.6 What is a ViewState?

In classic ASP, when a form is submitted the form values are cleared. In some cases the form is submitted with huge information. In such cases if the server comes back with error, one has to re-enter correct information in the form. But submitting clears up all form values. This happens as the site does not maintain any state (ViewState).

In ASP .NET, when the form is submitted the form reappears in the browser with all form values. This is because ASP .NET maintains your ViewState. ViewState is a state management technique built in ASP.NET. Its purpose is to keep the state of controls during subsequent postbacks by the same user. The ViewState indicates the status of the page when submitted to the server. The status is defined through a hidden field placed on each page with a <form runat="server"> control.

If you want to NOT maintain the ViewState, include the directive <%@ Page EnableViewState="false"%> at the top of an .aspx page If you do not want to maintain Viewstate for any control add the attribute EnableViewState="false" to any control. For more details refer The ASP.NET View State

2.7 Where can I get the details on Migration of existing projects using various technologies to ASP.NET?

Microsoft has designed Migration Assistants to help us convert existing pages and applications to ASP.NET. It does not make the conversion process completely automatic, but it will speed up project by automating some of the steps required for migration.
Below are the Code Migration Assistants

ASP to ASP.NET Migration Assistant
PHP to ASP.NET Migration Assistant
JSP to ASP.NET Migration Assistant

Refer Migrating to ASP.Net

2.8 What is the equivalent of date() and time() in ASP.NET?

VB.NET

System.DateTime.Now.ToShortDateString()

System.DateTime.Now.ToShortTimeString()

System.DateTime.Now.ToShortDateString();

System.DateTime.Now.ToShortTimeString();

2.9 How to prevent a button from validating it's form?

Set the CauseValidation property of the button control to False

2.10 How to get the IP address of the host accessing my site?

VB.NET

Response.Write (Request.UserHostAddress.ToString ())

Response.Write (Request.UserHostAddress.ToString ());

2.11 How to access the Parameters passed in via the URL?

Call the Request.QueryStringmethod passing in the key. The method will return the parameter value associated with that key. VB.NET

Request.QueryString("id")

Request.QueryString["id"];

2.12 How to Set Focus to Web Form Controls By Using Client-Side Script?

function SetFocus()

{

// W3C approved DOM code that will work in all modern browsers

if (document.getElementById)

document.getElementById('txt2').focus();

else

// To support older versions of IE:

if (document.all)

document.all("txt2").focus();

return false;

}

</script>

Enter 1:

<asp:TextBox ID="txt1" Runat="server" Width="50" />

<br>

Enter 2:

<asp:TextBox ID="txt2" Runat="server" Width="50" />

<br>

<asp:Button id="Button1" runat="server" Text="Button1"></asp:Button>

</form>

</body>

Refer Sample IE Code

2.13 How to display a Wait page while a query is running?

Refer Asynchronous Wait State Pattern in ASP.NET

2.14 How to implement Form based Authentication in ASP.NET application?

For

2.15 How to catch the 404 error in my web application and provide more useful information?

In the global.asax Application_error Event write the following code

VB.NET

Dim ex As Exception = Server.GetLastError().GetBaseException()

If TypeOf ex Is System.IO.FileNotFoundException Then

'your code

'Response.Redirect("err404.aspx")

Else

'your code

End If

Exception ex = Server.GetLastError().GetBaseException();

if (ex.GetType() == typeof(System.IO.FileNotFoundException))

{

//your code

Response.Redirect ("err404.aspx");

}

else

{

//your code

}

2.16 Is there a method similar to Response.Redirect that will send variables to the destination page other than using a query string or the post method?

Server.Transfer preserves the current page context, so that in the target page you can extract values and such. However, it can have side effects; because Server.Transfer doesnt' go through the browser, the browser doesn't update its history and if the user clicks Back, they go to the page previous to the source page.

Another way to pass values is to use something like a LinkButton. It posts back to the source page, where you can get the values you need, put them in Session, and then use Response.Redirect to transfer to the target page. (This does bounce off the browser.) In the target page you can read the Session values as required.

Refer to Passing Values Between Web Forms Pages for more information.

2.17 What are the differences between HTML versus Server Control?

Refer

2.18 How can I change the action of a form through code?

You can't change it. The action attribute is owned by ASP.NET. Handle Events and Transfer.

For work around refer to Paul Wilson's Multiple Forms and Non-PostBack Forms - Solution

2.19 Is there any control that allows user to select a time from a clock - in other words is there a clock control?

Peter Blum has developed some controls. Check out Peter's Date Package: TimeOfDayTextBox and DurationTextBox Controls

2.20 How to Compare time?

VB.NET

Dim t1 As String = DateTime.Parse("3:30 PM").ToString("t")

Dim t2 As String = DateTime.Now.ToString("t")

If DateTime.Compare(DateTime.Parse(t1), DateTime.Parse(t2)) < 0 Then

Response.Write(t1.ToString() & " is < than " & t2.ToString())

Else

Response.Write(t1.ToString() & " is > than " & t2.ToString())

End If

string t1 = DateTime.Parse("3:30 PM").ToString("t");

string t2 = DateTime.Now.ToString("t");

if (DateTime.Compare(DateTime.Parse (t1), DateTime.Parse (t2)) < 0 )

{

Response.Write(t1.ToString() + " is < than " + t2.ToString());

}

else

{

Response.Write(t1.ToString() + " is > than " + t2.ToString());

}

2.21 How To work with TimeSpan Class?

VB.NET

Dim adate As DateTime = DateTime.Parse("06/24/2003")

Dim bdate As DateTime = DateTime.Parse("06/28/2003")

Dim ts As New TimeSpan(bdate.Ticks - adate.Ticks)

Response.Write(ts.TotalDays & "<br>")

Response.Write(ts.TotalHours & ":" & ts.TotalMinutes & ":" & ts.TotalSeconds & ":" & ts.TotalMilliseconds)

DateTime adate = DateTime.Parse("06/24/2003");

DateTime bdate = DateTime.Parse("06/28/2003");

TimeSpan ts = new TimeSpan (bdate.Ticks - adate.Ticks);

Response.Write(ts.TotalDays.ToString () + "<br>");

Response.Write(ts.TotalHours.ToString() + ":" + ts.TotalMinutes.ToString() + ":" + ts.TotalSeconds.ToString() + ":" + ts.TotalMilliseconds.ToString() );

2.22 Where can I get information on Cookies in ASP.NET?

Refer Mike Pope's article Basics of Cookies in ASP.NET

2.23 Does ASP.Net still recognize the global.asa file?

ASP.Net does not recognize the standard ASP global.asa file. Instead it uses a file named global.asax with the same - plus additional - functionality.

2.24 How should I destroy my objects in ASP.Net?

ASP.Net actually has very solid internal garbage collection. So this is not an issue as it was in previous versions of Active Server Pages.
Link to more information: <gcConcurrent> Element

2.25 Are there resources online with tips on ASP to ASP.Net conversions?

Microsoft has deisnged The ASP to ASP.NET Migration Assistant help us convert ASP pages and applications to ASP.NET. It does not make the conversion process completely automatic, but it will speed up project by automating some of the steps required for migration.

The following Code Migration Assistants are discussed in the link below.

ASP to ASP.NET Migration Assistant
PHP to ASP.NET Migration Assistant
JSP to ASP.NET Migration Assistant

Refer Migrating to ASP.Net

Also refer:

Microsoft's ASP to ASP.NET Code Migration Assistant
John Peterson's article Microsoft's ASP to ASP.NET Migration Assistant
Paolo Cavone's article From ASP to ASP.NET... Painlessly!

2.26 How do I publish my ASP.NET application to my ISP's web server?

Your ISP must first create an IIS application and apply the Front Page Server Extensions to it. Then in Visual Studio .NET, select the "Project | Copy Project" menu. Then enter the URL and select the FrontPage web access method. The "Copy Project" feature copies all of the necessary files to your ISP's machine for your ASP.NET application to run.

You can also FTP your files to your ISP web server. But you must know which files to upload. For more details refer PRB: Remote ASP.NET Projects Require IIS on the Client Computer or FrontPage Server Extensions on the Server Computer

2.27 Why do i get error message "Could not load type" whenever I browse to my ASP.NET web site?

Your code-behind files for either your .aspx or the global.aspx page have not been complied. Use Visual Studio .NET's "Build | Build Solution" menu, or run the command line compiler.

For more details refer PRB: "Could not load type" error message when you browse to .aspx page

2.28 Will the WebMatrix SqlDataSourceControl work with a MySQL connection?

SqlDataSourceControl lets you connect and work with MS SQL DB, while AccessDataSourceControl do the same thing but for MS Access DB. Therefore SqlDataSourceControl can't help you in your MySql connectivity .
For Connectivity with MySql refer Accessing MySQL Database with ASP.NET

2.29 Can I combine classic ASP and ASP.NET pages?

No.
ASP pages can run in the same site as ASP.NET pages, but you can't mix in a page. Also ASP and ASP.NET won't share their session.

2.30 What is the difference between src and Code-Behind?

Src attribute means you deploy the source code files and everything is compiled JIT (just-in-time) as needed. Many people prefer this since they don't have to manually worry about compiling and messing with dlls -- it just works. Of course, the source is now on the server, for anyone with access to the server -- but not just anyone on the web.

CodeBehind attribute doesn't really "do" anything, its just a helper for VS.NET to associate the code file with the aspx file. This is necessary since VS.NET automates the pre-compiling that is harder by hand, and therefore the Src attribute is also gone. Now there is only a dll to deploy, no source, so it is certainly better protected, although its always decompilable even then.

2.31 How can I get the value of input box with type hidden in code-behind?

You can set the runat= server for the hidden control and you can use ControlName.Value to get its value in CodeBehind file

2.32 I have created a .NET user control page (.ascx) but I cannot compile and run it.

User control (ascx) can't be run on it own, but you can drag it onto any web page (aspx) and then run it.

2.33 What is a .resx file?

The .resx resource file format consists of XML entries, which specify objects and strings inside XML tags. This is useful for localization. For more details refer Resources in .resx files

2.34 Is it possible to use a style sheet class directly on a control instead of using inline or page-level formatting ?

Every WebControl derived control has a CssClass property which allows you to set it's format to a style sheet.

2.35 Can I recieve both HTML markup for page and code in the ASP.NET web page's source code portion in the Web browser?

No. The Web browser recieves only HTML markup.
No source code or web control syntax is passed back to the web browser.

2.36 Why can't I put <%@ Page Language="C " %> where at the top of an ASPX file and write my server-side scripts in C ?

The parsers ASP.NET uses to extract code from ASPX files understand C#, Visual Basic.NET, and JScript.NET. You can write server-side scripts in any language supported by a .NET compiler.

2.37 ASP pages that worked pefectly on Windows 2000 Server and IIS 5.0 do not work on Windows 2003 Server with IIS 6.0. ASP.NET pages work fine. Why?

Start -> Settings -> Control Panel -> Administrative Tools -> and double clicking IIS Manager.
Go to the Web Service Extensions tab, click Active Server Pages, then press the "Allow" button on the left

2.38 Why do I get error message "Error creating assembly manifest: Error reading key file 'key.snk' -- The system cannot find the file specified"?

Check the location of the key.snk file relative to the assembly file. Provide an explicit path or a relative path.

<Assembly: AssemblyKeyFileAttribute("Drive:\key.snk")>

2.39 How to get URL without querystring?

VB.NET

Dim stringUri As String = "http://www.syncfusion.com/?id=1&auid=16"

Dim weburi As Uri = New Uri(stringUri)

Dim query As String = weburi.Query

Dim weburl As String = stringUri.Substring(0, stringUri.Length - query.Length)

Response.Write(weburl)

string stringUri = "http://www.syncfusion.com/?id=1&auid=16";

Uri weburi = new Uri(stringUri);

string query = weburi.Query;

string weburl = stringUri.Substring(0, stringUri.Length - query.Length);

Response.Write (weburl);

2.40 What is the best way to output only time and not Date?

Use DateTime as follows VB.NET

Response.Write(DateTime.Now.ToString("hh:mm:ss"))

Response.Write(DateTime.Now.ToString("hh:mm:ss"));

2.41 Do I have to compile code if I am changing the content of my aspx.cs file?

Yes if you have used Codebehind="my.aspx.cs".
Not if you used src="my.aspx.cs" in your page declaration.

2.42 How to grab the referring URL?

VB.NET

Response.Write ( Request.UrlReferrer.ToString())

Response.Write ( Request.UrlReferrer.ToString());

2.43 My ASP code gives an error "Compiler Error Message: BC30289: Statement cannot appear within a method body. End of method assumed" when changed to .aspx?

Use a <script runat=server> block instead of the <% %> syntax to define Subs.
Make sure you have proper events associated with the code and have start and end of procedure or function wirtten properly.

2.44 How can I save images ?

You need a stream to read the response, WebResponse.GetResponseStream(), and a stream to write it to the hard drive. FileStream should do the trick. You'll have to write to the filestream what you read from the response stream.

2.45 How can I logout when using FormsAuthentication?

VB.NET

FormsAuthentication.SignOut()

FormsAuthentication.SignOut();

2.46 Why do I get a blank page when I use Server.Transfer("page1.htm") to transfer to a different page?

Server.Transfer only works with .aspx pages
You can't use Transfer method with HTML pages

2.47 How to detect the User's culture?

VB.NET

Dim sLang As String

sLang = Request.UserLanguages(0)

Response.Write(sLang)

string sLang ;

sLang = Request.UserLanguages[0];

Response.Write (sLang);

2.48 What is the difference between CurrentCulture property and the CurrentUICulture property?

CurrentCulture property : affects how the .NET Framework handles dates, currencies, sorting and formatting issues
CurrentUICulture property : determines which satellite assembly is used when loading resources

2.49 Can I read the hard disk serial # of the client computer using ASP.NET?

No. Such information is not passed to the server with a http request.

2.50 What is xxx(src As Object, e As EventArgs)?

xxx is an event handler
src is the object that fires the event
e is an event argument object that contains more information about the event
An event handler is used when one object wants to be notified when an event happens in another object

2.51 What is the difference between Absolute vs Relative URLs?

Absolute /Fully Qualified URLs:

Contain all information necessary for the browser(or other client program) to locate the resource named in the URL
- This includes protocol moniker used( i.e http://, ftp://..etc..), Server's Domain name or IP address and the file path
- Absolute URL looks as http://localhost/megasolutions/page1.aspx

Relative URLs:

Only provide information necessary to locate a resource relative to the current document(document relative) or current server or domain(root relative)
- Document relative URL - page1.aspx
- Root Relative URL - /megasolutions/Admin/pagelog.aspx

2.52 What is the difference between URL and URI?

A URL is the address of some resource on the Web, which means that normally you type the address into a browser and you get something back. There are other type of resources than Web pages, but that's the easiest conceptually. The browser goes out somewhere on the Internet and accesses something.

A URI is just a unique string that uniquely identifies something, commonly a namespace. Sometimes they look like a URL that you could type into the address bar of your Web browser, but it doesn't have to point to any physical resource on the Web. It is just a unique set of characters, that, in fact, don't even have to be unique.

URI is the more generic term, and a URL is a particular type of URI in that a URL has to uniquely identify some resource on the Web.

2.53 How to convert milliseconds into time?

VB.NET

dim ts as TimeSpan = TimeSpan.FromMilliseconds(10000)

Response.Write (ts.ToString () )

TimeSpan ts = TimeSpan.FromMilliseconds(10000);

Response.Write (ts.ToString () );

2.54 How to include multiple vb/cs files in the source?

You can do this using assembly directives.

<%@ assembly src="test1.vb" %>

<%@ assembly src="test2.vb" %>

<%@ assembly src="test1.cs" %>

<%@ assembly src="test2.cs" %>

However, note that each source file will be compiled individually into its own assembly, so they cannot have dependencies on each other.

2.55 How to convert a string to Proper Case?

Use the namespace System.Globalization
VB.NET

Dim myString As String = "syncFusion deVeloPer sUppOrt"

' Creates a TextInfo based on the "en-US" culture.

Dim TI As TextInfo = New CultureInfo("en-US", False).TextInfo

Response.Write(TI.ToTitleCase(myString))

string myString = "syncFusion deVeloPer sUppOrt";

// Creates a TextInfo based on the "en-US" culture.

TextInfo TI = new CultureInfo("en-US",false).TextInfo;

Response.Write (TI.ToTitleCase( myString ));

For more details refer TextInfo.ToTitleCase()

2.56 How can I ensure that application-level variables are not updated by more than one user simultaneously?

Use the HttpApplicationState's Lock and UnLock methods.

For more details refer : MSDN: Application State

2.57 Why do I get the error message "System.InvalidOperationException: It is invalid to show a modal dialog or form when the application is not running in UserInteractive mode. Specify the ServiceNotification or DefaultDesktopOnly style to display a ...."?

You can't use MsgBox or MessageBox.Show in ASP.NET WebForm. You maybe use:
VB.NET

Response.Write("<script>alert('Hello');</script>")

Response.Write("<script>alert('Hello');</script>") ;

2.58 How to validate that a string is a valid date?

VB.NET

Dim blnValid As Boolean = False

Try

DateTime.Parse(MyString)

blnValid = True

Catch

blnValid = False

End Try

bool blnValid=false;

try

{

DateTime.Parse(MyString);

blnValid=true;

}

catch

{

blnValid=false;

}

2.59 Are namespaces and Class names Case Sensitive?

Namespaces and Class names are case Sensitive. Namespaces imported using the @ Import Directive will cause an error if the correct case is not used.

2.60 How to convert string to a DateTime and compare it with another DateTime?

VB.NET

Dim blntimeIsOk As Boolean = DateTime.Parse("15:00") < DateTime.Parse("08:00")

Response.Write(blntimeIsOk)

bool blntimeIsOk = (DateTime.Parse("15:00") < DateTime.Parse("08:00"));

Response.Write (blntimeIsOk);

2.61 How to get the url of page dynamically?

Use Request.Url property

2.62 How to convert user input in dMy format to Mdy?

VB.NET

Dim dt As DateTime = DateTime.ParseExact("0299", New String() {"My", "M/y"}, Nothing, System.Globalization.DateTimeStyles.None)

DateTime dt = DateTime.ParseExact("0299", new string[] {"My","M/y"}, null,System.Globalization.DateTimeStyles.None);

For more details refer DateTime.ParseExact

2.63 When the User is prompted a File Download dialogbox, if the user selects "Save" then the "Save as" dialog box is displayed. Is there any way for me to retrieve the filename and directory path specified by the user on the File Download dialog box?

Clients do not report information back about where the user selects to save the content, so there isn't an easy way to do this. Instead, you would need to ask the user before using the content-disposition for a file path, and then you could specify the filename parameter for the content-disposition header. Still, the user is free to change that path when actually downloading.

2.64 How to hide or show Controls in server side code?

In any appropriate event write
VB.NET

TextBox1.Visible =not TextBox1.Visible

TextBox1.Visible =!TextBox1.Visible ;

2.65 How to check if the user is using a secure or non secure connection?

The Request Object defines a Property called IsSecureConnection, that will indicate whether http:// or https:// has been used.

2.66 Is it possible to write code in many languages in one ASP.NET project?

You cannot write the code-behind files in different languages in the same project, but you can write the aspx pages and ascx controls in different languages.

2.67 What is the difference between Response.Redirect() and Server.Transfer().

Response.Redirect

Tranfers the page control to the other page, in other words it sends the request to the other page.
Causes the client to navigate to the page you are redirecting to. In http terms it sends a 302 response to the client, and the client goes where it's told.

Server.Transfer

Only transfers the execution to another page and during this you will see the URL of the old page since only execution is transfered to new page and not control.
Occurs entirely on the server, no action is needed by the client

Sometimes for performance reasons, the server method is more desirable

2.68 How to get the hostname or IP address of the server?

You can use either of these:

HttpContext.Current.Server.MachineName
HttpContext.Current.Request.ServerVariables["LOCAL_ADDR"]

The first one should return the name of the machine, the second returns the local ip address.
Note that name of the machine could be different than host, since your site could be using host headers

2.69 What is the meaning of validateRequest=true in .net framework1.1?

The value of validateRequest is set to 'true' by default, which means that the framework will automatically deny submission of the '<' and '>' characters.

2.70 What is the different between <%# %> and <%= %>?

The <%# %> is used for databinding where as <%= %> is used to output the result of an expression. The expression inside <%# %> will be executed only when you call the page's or control's DataBind method. The expression inside <%= %> will be executed and displayed as and when it appears in the page.

2.71 What permissions do ASP.NET applications posses by default?

By default ASP.NET Web applications run as ASP.NET user. This user has limited permissions equivalent to the User Group.

2.72 How can I specify the relative path for a file?

Suppose you have following file hierarchy:

default.aspx

Admin/login.aspx

Misc/testpage.aspx

And you are on the login.aspx and want your user to navigate to the default.aspx (or testpage.aspx) file. Then you can use

Response.Redirect ("../default.aspx")
Response.Redirect ("../Misc/testpage.aspx")

2.73 How can I specify the "upload a file" input textbox in a form to be read only so that the user can click on the browse button and pick a file but they cannot type anything into the textbox next to the browse button.

2.74 How to change the Page Title dynamically?

VB.NET

'Declare

Protected WithEvents Title1 As System.Web.UI.HtmlControls.HtmlGenericControl

'In Page_Load

Title1.InnerText ="Page 1"

//Declare

protected System.Web.UI.HtmlControls.HtmlGenericControl Title1 ;

//In Page_Load

Title1.InnerText ="Page 1" ;

2.75 Why do I get the error message "Object must implement IConvertible". How can I resolve it?

The common cause for this error is specifying a control as a SqlParameter's Value instead of the control's text value.
For example, if you write code as below you'll get the above error:

VB.NET

Dim nameParameter As SqlParameter = command.Parameters.Add("@name", SqlDbType.NVarChar, 50)

nameParameter.Value = txtName

SqlParameter nameParameter = command.Parameters.Add("@name", SqlDbType.NVarChar, 50);

nameParameter.Value = txtName ;

To resolve it, specify the control's Text property instead of the control itself.

VB.NET

nameParameter.Value = txtName.Text

nameParameter.Value =txtName.Text;

2.76 Why is default.aspx page not opened if i specify http://localhost. I am able to view this page if i hardcode it as http://localhost/default.aspx?

If some other default page comes higher in the list, adjust the default.aspx to be the number one entry inside the IIS configuration. If you have multiple websites inside IIS, make sure the configuration is applied on the right website (or on all websites by applying the configuration on the server-level using the properties dialog, configure WWW service).

2.77 Can ASP.NET work on an NT server?

No. For more details refer ASP 1.1 version

2.78 Is it possible to migrate Visual InterDev Design-Time Controls to ASP.NET?

Refer INFO: Migrating Visual InterDev Design-Time Controls to ASP.NET

2.79 How to automatically get the latest version of all the asp.net solution items from Source Safe when opening the solution?

In VS.NET you can go to Tools > Options > Source Control > General and check the checkbox for Get everything when a solution opens.
This retrieves the latest version of all solution items when you open the solution.

2.80 How to convert the datetime into a string for use in the SQL ' statement?

<asp:label id="Label2" runat="server">Select a culture: </asp:label>

<asp:dropdownlist id="ddlCulture" runat="server" autopostback="True"></asp:dropdownlist>

<P></P>

<asp:label id="Label3" runat="server">DateTime in Selected Culture</asp:label>

<asp:textbox id="TextBox1" runat="server"></asp:textbox>

<p>

<asp:label id="Label1" runat="server"></asp:label>

VB.NET

Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

'Put user code to initialize the page here

If Not Page.IsPostBack Then

Dim cInfo As CultureInfo

For Each cInfo In CultureInfo.GetCultures(CultureTypes.SpecificCultures)

ddlCulture.Items.Add(cInfo.Name)

End If

End Sub

Private Sub ddlCulture_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ddlCulture.SelectedIndexChanged

' Get a CultureInfo object based on culture selection in dropdownlist

Dim cInfo As CultureInfo = New CultureInfo(ddlCulture.SelectedItem.Text)

' Get a CultureInfo object based on Invariant culture

Dim cInfoNeutral As CultureInfo = New CultureInfo("")

' Display the datetime based on the formatting of the selected culture

TextBox1.Text = Convert.ToString(Now, cInfo.DateTimeFormat)

' Create a DateTime variable to hold the Invariant time

Dim dt As DateTime

dt = Convert.ToDateTime(TextBox1.Text, cInfo.DateTimeFormat)

'Convert the datetime into a string for use in the SQL statement

Label1.Text = "... WHERE ([Date] < '" & _

Convert.ToString(dt, cInfoNeutral.DateTimeFormat) & "')"

End Sub

private void Page_Load(object sender, System.EventArgs e)

{

// Put user code to initialize the page here

if (!Page.IsPostBack )

{

foreach(CultureInfo cInfo in CultureInfo.GetCultures(CultureTypes.SpecificCultures))

{

ddlCulture.Items.Add(cInfo.Name);

}

private void ddlCulture_SelectedIndexChanged(object sender, System.EventArgs e)

{

// Get a CultureInfo object based on culture selection in dropdownlist

CultureInfo cInfo = new CultureInfo(ddlCulture.SelectedItem.Text);

// Get a CultureInfo object based on Invariant culture

CultureInfo cInfoNeutral = new CultureInfo("");

// Display the datetime based on the formatting of the selected culture

TextBox1.Text = Convert.ToString(DateTime.Now , cInfo.DateTimeFormat);

// Create a DateTime variable to hold the Invariant time

DateTime dt ;

dt = Convert.ToDateTime(TextBox1.Text, cInfo.DateTimeFormat);

//Convert the datetime into a string for use in the SQL statement

Label1.Text = "... WHERE ([Date] < '" + Convert.ToString(dt, cInfoNeutral.DateTimeFormat) + "')";

}

2.81 How to make VS.Net use FlowLayout as the default layout rather than the GridLayout?

For VB.NET, go to path C:\Program Files\Microsoft Visual Studio .NET\Vb7\VBWizards\WebForm\Templates\1033
Change the following line in the existing WebForm1.aspx

For C#, go to path C:\Program Files\Microsoft Visual Studio .NET 2003\VC#\VC#Wizards\CSharpWebAppWiz\Templates\1033
Change the following line in the existing WebForm1.aspx

Note:Before changing any templates it's a good idea to make backup copies of them
Or rather than above approach you can change the behavior for new files on a per project basis in Visual Studio by:

Right clicking on the project name (Ex: "WebApplication1)" in Solution Explorer, and select "Properties".
From project properties window, under Common Properties>Designer Defaults>Page Layout change "Grid" to "Flow".

2.82 Can I use a DataReader to update/insert/delete a record?

No. DataReader provides a means of reading a forward-only stream of rows from a database.

2.83 What is the difference between Server.Transfer and Server.Execute?

Server.Transfer is used to End the current weform and begin executing a new webform. This method works only when navigating to a Web Forms page (.aspx)
Server.Execute is used to begin executing a new webform while still displaying the current web form. The contents of both forms are combined. This method works only when navigating to a webform page(.aspx)

2.84 How to create a login screen in ASP.NET?

Here is a sample login screen:

<TR>

<TD>

<asp:Label id="Label1" runat="server">User Name</asp:Label></TD>

<TD>

<asp:TextBox id="txtUserName" runat="server"></asp:TextBox></TD>

<TD>

<asp:RequiredFieldValidator id="RequiredFieldValidator1" runat="server" ErrorMessage="*" ControlToValidate="txtUserName"></asp:RequiredFieldValidator></TD>

</TR>

<TR>

<TD>

<asp:Label id="Label2" runat="server">Password</asp:Label></TD>

<TD>

<asp:TextBox id="txtPassword" runat="server"></asp:TextBox></TD>

<TD>

<asp:RequiredFieldValidator id="RequiredFieldValidator2" runat="server" ErrorMessage="*" ControlToValidate="txtPassword"></asp:RequiredFieldValidator></TD>

</TR>

<TR>

<TD>

<asp:Button id="btnLogin" runat="server" Text="Login"></asp:Button></TD>

</TR>

</TABLE>

VB.NET

Dim myconnection As SqlConnection

Dim mycmd As SqlCommand

Dim strSql As String

Dim myReader As SqlDataReader

Private Sub btnLogin_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnLogin.Click

myconnection=NewSqlConnection("Server=localhost;uid=sa;password=;database=northwind;")

strSql = "Select * from usertbl where username=" & "'" & txtUserName.Text & "'" & " and userpassword=" & "'" & txtPassword.Text & "'"

mycmd = New SqlCommand(strSql, myconnection)

myconnection.Open()

myReader = mycmd.ExecuteReader(CommandBehavior.CloseConnection)

If myReader.Read() Then

Response.Write("Welcome")

Else

Response.Write("Access Denied")

End If

End Sub

SqlConnection myconnection ;

SqlCommand mycmd ;

string strSql ;

SqlDataReader myReader ;

private void btnLogin_Click(object sender, System.EventArgs e)

{

myconnection=newSqlConnection("Server=localhost;uid=sa;password=;database=northwind;");

strSql = "Select * from usertbl where username=" + "'" + txtUserName.Text + "'" + " and userpassword=" + "'" + txtPassword.Text + "'";

mycmd = new SqlCommand(strSql, myconnection);

myconnection.Open();

myReader = mycmd.ExecuteReader(CommandBehavior.CloseConnection);

if (myReader.Read() )

{

Response.Write("Welcome");

}

else

{

Response.Write("Access Denied");

}

2.85 How to format a Telphone number in the xxx-xxx-xxxx format?

VB.NET

Dim Telno As Double = Double.Parse(ds.Tables(0).Rows(0)("TelNo").ToString())

Response.Write(Telno.ToString("###-###-####"))

double Telno= double.Parse(ds.Tables[0].Rows[0]["TelNo"].ToString());

Response.Write(Telno.ToString("###-###-####"));

2.86 Can two different programming languages be mixed in a single ASPX file?

No. ASP.NET uses parsers to strip the code from ASPX files and copy it to temporary files containing derived Page classes, and a given parser understands only one language

2.87 Can I use custom .NET data types in a Web form?

Yes. Place the DLL containing the type in the application root's bin directory and ASP.NET will automatically load the DLL when the type is referenced. This is also what happens when you add a custom control from the toolbox to your web form.

2.88 How can I have a particular Web page in an ASP.NET application which displays its own error page.

This can be done by setting the ErroPage attribute of Page Directive or ErrorPage property of Page Class to the desired Custom Error Page

<%@Page Language="C#" ErrorPage="specificerropage.htm"%>

In web.config

Asp.Net FAQs

Asp.NET 2.0 Qs

Knowledgebase

Articles

Code Walkthroughs

Discussion Forums

2. Basic

2.1 What is ASP.NET?

2.2 Why does my ASP.NET file have multiple <form> tag with runat=server?

2.3 How to find out what version of ASP.NET I am using on my machine?

2.4 Is it possible to pass a querystring from an .asp page to aspx page?

2.5 How to comment out ASP.NET Tags?

2.6 What is a ViewState?

2.7 Where can I get the details on Migration of existing projects using various technologies to ASP.NET?

2.8 What is the equivalent of date() and time() in ASP.NET?

2.9 How to prevent a button from validating it's form?

2.10 How to get the IP address of the host accessing my site?

2.11 How to access the Parameters passed in via the URL?

2.12 How to Set Focus to Web Form Controls By Using Client-Side Script?

2.13 How to display a Wait page while a query is running?

2.14 How to implement Form based Authentication in ASP.NET application?

2.15 How to catch the 404 error in my web application and provide more useful information?

2.16 Is there a method similar to Response.Redirect that will send variables to the destination page other than using a query string or the post method?

2.17 What are the differences between HTML versus Server Control?

2.18 How can I change the action of a form through code?

2.19 Is there any control that allows user to select a time from a clock - in other words is there a clock control?

2.20 How to Compare time?

2.21 How To work with TimeSpan Class?

2.22 Where can I get information on Cookies in ASP.NET?

2.23 Does ASP.Net still recognize the global.asa file?

2.24 How should I destroy my objects in ASP.Net?

2.25 Are there resources online with tips on ASP to ASP.Net conversions?

2.26 How do I publish my ASP.NET application to my ISP's web server?

2.27 Why do i get error message "Could not load type" whenever I browse to my ASP.NET web site?

2.28 Will the WebMatrix SqlDataSourceControl work with a MySQL connection?

2.29 Can I combine classic ASP and ASP.NET pages?

2.30 What is the difference between src and Code-Behind?

2.31 How can I get the value of input box with type hidden in code-behind?

2.32 I have created a .NET user control page (.ascx) but I cannot compile and run it.

2.33 What is a .resx file?

2.34 Is it possible to use a style sheet class directly on a control instead of using inline or page-level formatting ?

2.35 Can I recieve both HTML markup for page and code in the ASP.NET web page's source code portion in the Web browser?

2.36 Why can't I put <%@ Page Language="C " %> where at the top of an ASPX file and write my server-side scripts in C ?

2.37 ASP pages that worked pefectly on Windows 2000 Server and IIS 5.0 do not work on Windows 2003 Server with IIS 6.0. ASP.NET pages work fine. Why?

2.38 Why do I get error message "Error creating assembly manifest: Error reading key file 'key.snk' -- The system cannot find the file specified"?

2.39 How to get URL without querystring?

2.40 What is the best way to output only time and not Date?

2.41 Do I have to compile code if I am changing the content of my aspx.cs file?

2.42 How to grab the referring URL?

2.43 My ASP code gives an error "Compiler Error Message: BC30289: Statement cannot appear within a method body. End of method assumed" when changed to .aspx?

2.44 How can I save images ?

2.45 How can I logout when using FormsAuthentication?

2.46 Why do I get a blank page when I use Server.Transfer("page1.htm") to transfer to a different page?

2.47 How to detect the User's culture?

2.48 What is the difference between CurrentCulture property and the CurrentUICulture property?

2.49 Can I read the hard disk serial # of the client computer using ASP.NET?

2.50 What is xxx(src As Object, e As EventArgs)?

2.51 What is the difference between Absolute vs Relative URLs?

2.52 What is the difference between URL and URI?

2.53 How to convert milliseconds into time?

2.54 How to include multiple vb/cs files in the source?

2.55 How to convert a string to Proper Case?

2.56 How can I ensure that application-level variables are not updated by more than one user simultaneously?

2.57 Why do I get the error message "System.InvalidOperationException: It is invalid to show a modal dialog or form when the application is not running in UserInteractive mode. Specify the ServiceNotification or DefaultDesktopOnly style to display a ...."?

2.58 How to validate that a string is a valid date?

2.59 Are namespaces and Class names Case Sensitive?

2.60 How to convert string to a DateTime and compare it with another DateTime?

2.61 How to get the url of page dynamically?

2.62 How to convert user input in dMy format to Mdy?

2.63 When the User is prompted a File Download dialogbox, if the user selects "Save" then the "Save as" dialog box is displayed. Is there any way for me to retrieve the filename and directory path specified by the user on the File Download dialog box?

2.64 How to hide or show Controls in server side code?

2.65 How to check if the user is using a secure or non secure connection?

2.66 Is it possible to write code in many languages in one ASP.NET project?

2.67 What is the difference between Response.Redirect() and Server.Transfer().

2.68 How to get the hostname or IP address of the server?

2.69 What is the meaning of validateRequest=true in .net framework1.1?

2.70 What is the different between <%# %> and <%= %>?

2.71 What permissions do ASP.NET applications posses by default?

2.72 How can I specify the relative path for a file?

2.73 How can I specify the "upload a file" input textbox in a form to be read only so that the user can click on the browse button and pick a file but they cannot type anything into the textbox next to the browse button.