22. Controls

FAQ Home

22.1	How to close the browser window on button control click?

22.2	How to create server controls at runtime?

22.3	How to change the text color of a linkbutton control?

22.4	How to dynamically add validator controls?

22.5	How to change the image button size during runtime?

22.6	How can I to divide the .aspx page to different parts with different functionality in a neat and organized manner. Is there any control that can do that?

22.7	How to maintain Scroll Position in any Page Element?

22.8	DataBinder.Eval imposes performance penalty on code as it uses late bound reflection. How can I replace this calls with explicit calls?

22.9	What is the difference between User Controls and Custom Controls?

22.10

How to apply Style to a Web Server control programmatically?

22.11

How can I disable a button to prevent the user from multiple clicking?

22.12

Why do I get the error message "Access is denied : <myctrl>" when I try to load a Custom Control?

22.13

How to pass information between panels. Information entered in one panel should be displayed in other panel?

22.14

Why do I get error message "The control '_ctl1' of type 'TextBox' must be inside a form label with runat=server" while trying to place a control inside a form dynamically?

22.15

How to implement mouseover effects in a <asp:image> web server control?

22.16

Is there a way to set the position of the controls dynamically?

22.17

How can I set the maximum and minimum value for RangeValidator based on two dates?

22.18

How to specifiy the hspace and vspace in a <asp:Image>?

22.19

How to disable status bar messages for Hyperlink Controls?

22.20

How to get the list of all System.Web.UI.WebControls in my page?

22.21

How to set the vertical align of a TableCell programmatically?

22.22

How to control viewstate on individual controls?

22.1 How to close the browser window on button control click?

Method 1. This will cause a postback on button click in response to which we will send some script to close the window.

VB.NET

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

Response.Write("<script>window.close();</script>")

End Sub

C#

private void Button1_Click(object sender, System.EventArgs e)

{

Response.Write("<script>window.close();</script>");

}

Method 2. This is preferrable since there is no postback involved.

Use the Attribute collections i.e use Attributes of button control to add client side JavaScript code

VB.NET

Button1.Attributes.Add("OnClick", "window.close();")

C#

Button1.Attributes.Add("OnClick", "window.close();");

22.2 How to create server controls at runtime?

Here is an example of creating a HyperLink control in code. VB.NET

Dim hpl As New HyperLink()

hpl.Text="Text"

hpl.NavigateUrl="http://www.syncfusion.com"'

hpl.ID="theID"

Page.Controls(1).Controls.Add(hpl)

C#

HyperLink hpl = new HyperLink();

hpl.Text="Text";

hpl.NavigateUrl="http://www.syncfusion.com";

hpl.ID="theID";

Page.Controls[1].Controls.Add(hpl);

22.3 How to change the text color of a linkbutton control?

<asp:LinkButton forecolor ="green" id="LinkButton1" runat="server">LinkButton</asp:LinkButton>

22.4 How to dynamically add validator controls?

VB.NET

Dim i As Integer = 1

'Textbox

Dim txtBox As TextBox = New TextBox

txtBox.ControlStyle.CssClass = "textbox"

txtBox.ID = "txtbox" + i.ToString()

'RequiredFieldValidator

Dim rqdVal As RequiredFieldValidator = New RequiredFieldValidator

rqdVal.ID = "rqdVal" + i.ToString()

rqdVal.ControlToValidate = "txtbox" + i.ToString()

rqdVal.ErrorMessage = "Please enter a value"

rqdVal.Display = ValidatorDisplay.Dynamic

'RangeValidator

Dim rngVal As RangeValidator = New RangeValidator

rngVal.ID = "rngVal" + i.ToString()

rngVal.MinimumValue = "1"

rngVal.MaximumValue = "100"

rngVal.ControlToValidate = "txtbox" + i.ToString()

rngVal.Type = ValidationDataType.Double

rngVal.ErrorMessage = " Value should be between 1 and 100"

'Add Controls on the page

Page.Controls(1).Controls.Add(txtBox)

Page.Controls(1).Controls.Add(rqdVal)

Page.Controls(1).Controls.Add(rngVal)

C#

int i=1;

//Textbox

TextBox txtBox = new TextBox();

txtBox.ControlStyle.CssClass = "textbox";

txtBox.ID = "txtbox" + i.ToString();

//RequiredFieldValidator

RequiredFieldValidator rqdVal = new RequiredFieldValidator();

rqdVal.ID = "rqdVal" + i.ToString();

rqdVal.ControlToValidate = "txtbox" + i.ToString();

rqdVal.ErrorMessage = "Please enter a value";

rqdVal.Display =ValidatorDisplay.Dynamic;

//RangeValidator

RangeValidator rngVal = new RangeValidator();

rngVal.ID = "rngVal" + i.ToString();

rngVal.MinimumValue = "1";

rngVal.MaximumValue = "100";

rngVal.ControlToValidate = "txtbox" + i.ToString();

rngVal.Type = ValidationDataType.Double;

rngVal.ErrorMessage = " Value should be between 1 and 100";

//Add Controls on the page

Page.Controls[1].Controls.Add (txtBox);

Page.Controls[1].Controls.Add (rqdVal);

Page.Controls[1].Controls.Add (rngVal);

22.5 How to change the image button size during runtime?

VB.NET

Dim x As New Unit("80px")

Dim y As New Unit("20px")

Dim imagestate as string= "stand"

If imagestate = "stand" then

imagebutton1.height = x

else

imagebutton1.height = y

end if

C#

Unit x = new Unit ("80px");

Unit y = new Unit("20px");

string imagestate="stand";

if( imagestate != "stand")

{

ImageButton1.Height = x;

}

else

{

ImageButton1.Height = y;

}

For more details Setting Web Server Control Properties Programmatically

22.6 How can I to divide the .aspx page to different parts with different functionality in a neat and organized manner. Is there any control that can do that?

You can use Panel controls, which render as HTML div elements. You can then show or hide the panels by enabling/disabling them. In addition, you can specify different formatting options for different Panels/divs using manual formatting or CSS styles.

22.7 How to maintain Scroll Position in any Page Element?

Check out Jim Ross's article Maintain Scroll Position in any Page Element The article describes, when using a scrollable Datagrid--one inside an overflow-auto DIV control--how to maintain the user's scroll position inside the DIV across postbacks. It does this using IE behaviors, HTC files.

22.8 DataBinder.Eval imposes performance penalty on code as it uses late bound reflection. How can I replace this calls with explicit calls?

Change the Databinding Expression

<%#DataBinder.Eval (Container.DataItem , "StartDate" , "{0:c}")%>

to In VB.NET

<%#String.Format("{0:d}" , (CType(Container.DataItem, DataRowView))("StartDate"))%>

C#

<%#String.Format("{0:d}" , ((DataRowView)Container.DataItem)["StartDate"])%>

22.9 What is the difference between User Controls and Custom Controls?

User Controls are text files with the extension '.ascx' which enables you to make GUI re-usable controls. Its a text file, which contains a mixture of HTML and scripting. User Controls can be edited in an editor. On the other hand Custom Controls reside in compiled ( Dll ) assemblies. They are non-GUI but can emit HTML GUI at runtime. Example of Custom Controls would be the sever controls which come bundled with the .NET SDK like DataGrid, Repeater, DataList etc. Custom Controls are always compiled into Dll's and hence require good programming knowledge. The purpose of Custom Controls is also to create re-usable units of code.

22.10 How to apply Style to a Web Server control programmatically?

User Interface

<asp:TextBox id="TextBox1" style="Z-INDEX: 101; LEFT: 40px; POSITION: absolute; TOP: 64px" runat="server">Syncfusion</asp:TextBox>

<asp:Button id="Button1" style="Z-INDEX: 102; LEFT: 48px; POSITION: absolute; TOP: 120px" runat="server" Text="Button"></asp:Button>

<asp:CheckBox id="CheckBox1" style="Z-INDEX: 103; LEFT: 40px; POSITION: absolute; TOP: 200px" runat="server" Text="Syncfusion"></asp:CheckBox>

VB.NET Create a function

Protected Function createStyleForControl(ByVal _forecolor As Color, ByVal _backcolor As Color, ByVal _fontbold As Boolean) As Style

Dim s As Style = New Style

s.ForeColor = _forecolor

s.BackColor = _backcolor

s.Font.Bold = _fontbold

Return s

End Function

In Page_Load

Dim textboxStyle As Style = createStyleForControl(Color.Pink, Color.Yellow, False)

Dim buttonStyle As Style = createStyleForControl(Color.Blue, Color.Teal, True)

Dim checkboxStyle As Style = createStyleForControl(Color.AliceBlue, Color.PowderBlue, False)

TextBox1.ApplyStyle(textboxStyle)

Button1.ApplyStyle(buttonStyle)

CheckBox1.ApplyStyle(checkboxStyle)

C# Create a function

protected     Style createStyleForControl(Color _forecolor ,Color _backcolor ,bool _fontbold )

{

Style s = new Style();

s.ForeColor = _forecolor;

s.BackColor =_backcolor;

s.Font.Bold = _fontbold;

return s;

}

In Page_Load

Style textboxStyle=createStyleForControl (Color.Pink , Color.Yellow ,false );

Style buttonStyle=createStyleForControl (Color.Blue , Color.Teal ,true );

Style checkboxStyle =createStyleForControl (Color.AliceBlue , Color.PowderBlue ,false );

TextBox1.ApplyStyle(textboxStyle );

Button1.ApplyStyle (buttonStyle );

CheckBox1.ApplyStyle (checkboxStyle );

22.11 How can I disable a button to prevent the user from multiple clicking?

In the very last line of the button1_Click subroutine, add this line: VB.NET

Button1.Enabled = False

C#

Button1.Enabled =false;

22.12 Why do I get the error message "Access is denied : <myctrl>" when I try to load a Custom Control?

This is a common problem in ASP.NET. It happens because some program is scanning the Temporary ASP.NET files folders where your assemblies are copied. They have the files open in a mode that prevents ASP.NET itself from using the assembly file. For solution refer PRB: Access Denied Error When You Make Code Modifications with Index Services Running

22.13 How to pass information between panels. Information entered in one panel should be displayed in other panel?

<asp:Panel id="Panel1" runat="server" Width="271px" Height="41px">

<TABLE id="Table1" cellSpacing="1" cellPadding="1" width="300" border="1">

<TR>

<TD>

<P><asp:TextBox id="TextBox1" runat="server"></asp:TextBox></P>

</TD>

</TR>

<TR>

<TD>

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

</TR>

</TABLE>

</asp:Panel>

<asp:Panel id="Panel2" style="Z-INDEX: 102; LEFT: 16px; POSITION: absolute; TOP: 120px" runat="server"

Width="176px" Height="91px" Visible="False">

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

</asp:Panel>

On Button Click VB.NET

Panel2.Visible =true

Label1.Text = TextBox1.Text

C#

Panel2.Visible =true;

Label1.Text = TextBox1.Text ;

Note: Based on the criteria you can hide and show panels

22.14 Why do I get error message "The control '_ctl1' of type 'TextBox' must be inside a form label with runat=server" while trying to place a control inside a form dynamically?

You are probably adding the textbox into the Page directly instead of adding it to the Page's form. Try doing this: VB.NET

Me.Page.Controls(1).Controls.Add(txtboxctrl)

C#

this.Page.Controls[1].Controls.Add(txtboxctrl);

22.15 How to implement mouseover effects in a <asp:image> web server control?

<asp:Image id="Image1" runat="server" ImageUrl="b2346.jpg"></asp:Image>

VB.NET

Image1.Attributes.Add("onmouseover", "this.src='b2456.jpg'")

C#

Image1.Attributes.Add("onmouseover", "this.src='b2456.jpg'");

22.16 Is there a way to set the position of the controls dynamically?

Yes.

<asp:Button id="Button1" style="Z-INDEX: 101; LEFT: 116px; POSITION: absolute; TOP: 152px" runat="server"

Text="Move"></asp:Button>

<asp:RadioButtonList id="RadioButtonList1" style="Z-INDEX: 103; LEFT: 87px; POSITION: absolute; TOP: 27px"

runat="server" AutoPostBack="True">

<asp:ListItem Value="10px">10 pixels</asp:ListItem>

<asp:ListItem Value="100px">100 pixels</asp:ListItem>

<asp:ListItem Value="200px">200 pixels</asp:ListItem>

</asp:RadioButtonList>

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

Button1.Style.Add("LEFT", "1px")

End If

End Sub 'Page_Load

Private Sub RadioButtonList1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles RadioButtonList1.SelectedIndexChanged

Button1.Style.Add("LEFT", RadioButtonList1.SelectedItem.Value.ToString())

End Sub 'RadioButtonList1_SelectedIndexChanged

C#

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

{

// Put user code to initialize the page here

if (!Page.IsPostBack )

{

Button1.Style.Add("LEFT", "1px");

}

}

private void RadioButtonList1_SelectedIndexChanged(object sender, System.EventArgs e)

{

Button1.Style.Add("LEFT",RadioButtonList1.SelectedItem.Value.ToString());

}

22.17 How can I set the maximum and minimum value for RangeValidator based on two dates?

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

<asp:rangevalidator id="RangeValidator1" type="Date" controltovalidate="TextBox1" runat="server" errormessage="Not in range" />

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

VB.NET

...

Dim dtMinDate As DateTime

Dim dtMaxDate As DateTime

dtMinDate = Convert.ToDateTime("04/25/04")

dtMaxDate = Convert.ToDateTime("10/17/04")

RangeValidator1.MinimumValue = dtMinDate

RangeValidator1.MaximumValue = dtMaxDate

TextBox1.Text = dtMaxDate.ToShortDateString

RangeValidator1.ErrorMessage = "Not in Range of " & dtMinDate.ToShortDateString() & " to " & dtMaxDate.ToShortDateString()

C#

DateTime dtMinDate ;

DateTime dtMaxDate ;

dtMinDate = Convert.ToDateTime("04/25/04");

dtMaxDate = Convert.ToDateTime("10/17/04");

RangeValidator1.MinimumValue = dtMinDate.ToShortDateString () ;

RangeValidator1.MaximumValue = dtMaxDate.ToShortDateString () ;

TextBox1.Text = dtMaxDate.ToShortDateString();

RangeValidator1.ErrorMessage = "Not in Range of " + dtMinDate.ToShortDateString() + " to " + dtMaxDate.ToShortDateString();

22.18 How to specifiy the hspace and vspace in a <asp:Image>?

VB.NET

Image1.Attributes.Add("hspace", "50")

Image1.Attributes.Add("vspace", "50")

C#

Image1.Attributes.Add("hspace", "50") ;

Image1.Attributes.Add("vspace", "50") ;

22.19 How to disable status bar messages for Hyperlink Controls?

VB.NET

HyperLink1.Attributes.Add("onMouseOver", "window.status=' '; return true;")

C#

HyperLink1.Attributes.Add("onMouseOver", "window.status=' '; return true;") ;

22.20 How to get the list of all System.Web.UI.WebControls in my page?

<asp:Repeater runat="server" DataSource='<%# GetControls() %>' ID="Repeater1">

<HeaderTemplate>

<ul>

</HeaderTemplate>

<ItemTemplate>

<li>

<%# DataBinder.Eval(Container.DataItem, "Name") %>

</li>

</ItemTemplate>

<FooterTemplate>

</ul>

</FooterTemplate>

</asp:Repeater>

VB.NET

Protected Function GetControls() As ArrayList

Dim arrList As New ArrayList()

Dim t As Type

For Each t In GetType(Page).Assembly.GetTypes()

If t.Namespace = "System.Web.UI.WebControls" And GetType(Control).IsAssignableFrom(t) Then

arrList.Add(t)

End If

Next

Return arrList

End Function 'GetControls

'In Page_Load

DataBind()

C#

protected     ArrayList GetControls()

{

ArrayList arrList = new ArrayList();

foreach (Type t in typeof(Page ).Assembly.GetTypes())

{

if (t.Namespace == "System.Web.UI.WebControls" && typeof(Control).IsAssignableFrom(t))

arrList.Add(t);

}

return arrList;

}

//In Page_Load

DataBind();

22.21 How to set the vertical align of a TableCell programmatically?

VB.NET

Dim tbl As New TableCell()

'VerticalAlign is enumeration in System.Web.UI.WebControls namespace

tbl.VerticalAlign = VerticalAlign.Top

C#

TableCell tbl=new TableCell();

//VerticalAlign is enumeration in System.Web.UI.WebControls namespace

tbl.VerticalAlign = VerticalAlign.Top;

22.22 How to control viewstate on individual controls?

You can set the EnableViewState property of the control. You should disable viewstate for any control that doesn't use it to gurantee optimum performance.