Utility for rendering HTMLTable control containing ASP .Net form elements into string

By | September 24, 2005

Introduction

Many websites have some kind of contact form as shown in the following figure. User fills details and presses the “Send” button. This form takes input from the textbox, checkbox, radiobutton etc, builds string containing html and sends information as HTML email. If the form is expecting many values from user, the developer has to write down big chunk of HTML code in the backend. If the developer has to build more than one such forms, it is really cumbersome. To reduce the precious time of developer, this utility module is developed.

HTML Utility Snap 1

Problem in Direct Rendering of Control

We can use directly Control.Render() method to render html in HTMLTextWriter but with the condition that there should not be any webform controls like TextBox, Label etc. If still we are using this method, it will give error because each server control must be rendered within “form” tag which is having “runat=server” attribute.

Utility Module

Public Function GetHTML(ByVal objControl As Control) As String
	Dim sb As New System.Text.StringBuilder
	GenerateHTML(objControl, sb)
	Return sb.ToString
End Function

This function takes as argument the control object of which we need to get HTML. It will call private method GenerateHTML() which is responsible for generating HTML for the control.

Private Sub GenerateHTML(ByVal objControl As Control, ByVal sb As System.Text.StringBuilder)
	Dim str As New System.Text.StringBuilder
	Dim sw As New System.IO.StringWriter(str)
	Dim hw As New System.Web.UI.HtmlTextWriter(sw)
	If TypeOf (objControl) Is HtmlTable Then
		sb.Append("<table ")
		CType(objControl, HtmlTable).Attributes.Render(hw)
		sb.Append(str.ToString & " >")
		Dim objControl1 As Control
		For Each objControl1 In objControl.Controls
			GenerateHTML(objControl1, sb)
		Next
		sb.Append("</table>")
	ElseIf TypeOf (objControl) Is HtmlTableRow Then
		sb.Append("<tr ")
		CType(objControl, HtmlTableRow).Attributes.Render(hw)
		sb.Append(str.ToString & " >")
		Dim objControl1 As Control
		For Each objControl1 In objControl.Controls
			GenerateHTML(objControl1, sb)
		Next
		sb.Append("</tr>")
	ElseIf TypeOf (objControl) Is HtmlTableCell Then
		sb.Append("<td ")
		CType(objControl, HtmlTableCell).Attributes.Render(hw)
		sb.Append(str.ToString & " >")
		Dim objControl1 As Control
		For Each objControl1 In objControl.Controls
			GenerateHTML(objControl1, sb)
		Next
		sb.Append("</td>")
	ElseIf TypeOf (objControl) Is LiteralControl Then
		sb.Append(CType(objControl, LiteralControl).Text)
	ElseIf TypeOf (objControl) Is TextBox Then
		sb.Append(CType(objControl, TextBox).Text)
	ElseIf TypeOf (objControl) Is Label Then
		sb.Append(CType(objControl, Label).Text)
	ElseIf TypeOf (objControl) Is CheckBox Then
		Dim chk As CheckBox = CType(objControl, CheckBox)
		sb.Append("<input type='checkbox'" & IIf(chk.Checked, "Checked ", " >") & chk.Text)
	ElseIf TypeOf (objControl) Is RadioButton Then
		Dim rad As RadioButton = CType(objControl, RadioButton)
		sb.Append("<input type='radio'" & IIf(rad.Checked, "Checked >", " >") & rad.Text)
	End If
End Sub

This function uses recursion to get each element from control hierarchy. It renders HTML code for the control. Currently it supports, HTMLTable, TextBox, CheckBox, RadioButton, Label, and LiteralControl. As this function uses recursion, the processing may be slower than hardcoding the HTML string. So I wrote other function GetCode() which is responsible for emitting source code for building HTML string. This code you can put in a function and get HTML string of the control. The output of both methods are shown in figure.

HTML Utility Result Snap

Conclusion

If webform is not used very frequently, developer should use, GetHTML() function otherwise they should use use and throw function GetCode(), generate the code, put the code in file and remove this function from solution.

4 thoughts on “Utility for rendering HTMLTable control containing ASP .Net form elements into string

  1. Anandkumar

    Given solution is good.
    My Question is How can I apply styles to the htmltable?
    How can I change style of the particular row or cell?

  2. badar

    hi thier is a problem in the server controls
    when i type inside a text it didnt didnt apper the text
    why

  3. ahmed dami

    To render the html for a html table I used the code below and worked fine for me
    HtmlTable tbl = new HtmlTable ();
    // Add the rows and cells here
    //……….

    // Rendring the html of the html control
    StringBuilder sb = new StringBuilder();
    HtmlTextWriter htmltw = new HtmlTextWriter(new StringWriter(sb) ,”\t”);
    tbl.RenderControl(htmltw);

    return sb.ToString();

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