Set Initial Focus on an ASP.NET Page
Easily generate the Javascript to set focus to any control on your ASP.NET page
By
Steve on
Tuesday, January 09, 2007
Updated
Friday, April 22, 2016
Viewed
37,844 times. (
0 times today.)
Summary
Setting the cursor focus to a particular element of a web page when it loads is a pretty common little feature, but it can be annoying to implement. Here I automated the process in a C# method. You only need to pass the Control to the method and it will register the Javascript and set focus on page load.
This code was adapted from work by Fons.Sonnemans@reflectionit.nl.
Setup a couple of text boxes to test by adding the following to your aspx page.
Example: How to use the SetInitialFocus method
<P><asp:TextBox id="TextBox1" runat="server"></asp:TextBox>
<P><INPUT id="htmlTextBox" type="text" runat="server">
Then call the following method from the Page_Load in the code behind file. Notice that this works for WebControls and HtmlControls.
Example: How to use the SetInitialFocus method
public void TestSetInitialFocus()
{
//Snippets00004.SetInitialFocus(TextBox1);
Snippets00004.SetInitialFocus(htmlTextBox);
}
If you load the test aspx page in your browser, you should see that the selected control has the cursor focus.
Here's the class:
The SetInitialFocus method embedded in a class.
namespace Cambia.CoreLib
{
using System;
using System.Text;
using System.Web.UI;
using System.Web.UI.WebControls;
/// <summary>
/// Useful C# snippets from CambiaResearch.com
/// </summary>
public class Snippets00004
{
public Snippets00004()
{
}
public static void SetInitialFocus(Control control)
{
if (control.Page.IsClientScriptBlockRegistered("InitialFocus"))
return;
if (control.Page == null)
{
throw new ArgumentException(
"The Control must be added to a Page before "
+ "you can set the IntialFocus to it.");
}
if (control.Page.Request.Browser.JavaScript == true)
{
// Create JavaScript
StringBuilder s = new StringBuilder();
s.Append("\n<SCRIPT LANGUAGE='JavaScript'>\n");
s.Append("<!--\n");
s.Append("function SetInitialFocus()\n");
s.Append("{\n");
s.Append(" document.");
// Find the Form
Control p = control.Parent;
while (!(p is System.Web.UI.HtmlControls.HtmlForm))
p = p.Parent;
s.Append(p.ClientID);
s.Append("['");
s.Append(control.UniqueID);
// Set Focus on the selected item of a RadioButtonList
RadioButtonList rbl = control as RadioButtonList;
if (rbl != null)
{
string suffix = "_0";
int t = 0;
foreach (ListItem li in rbl.Items)
{
if (li.Selected)
{
suffix = "_" + t.ToString();
break;
}
t++;
}
s.Append(suffix);
}
// Set Focus on the first item of a CheckBoxList
if (control is CheckBoxList)
{
s.Append("_0");
}
s.Append("'].focus();\n");
s.Append("}\n");
if (control.Page.SmartNavigation)
s.Append("window.setTimeout(SetInitialFocus, 500);\n");
else
s.Append("window.onload = SetInitialFocus;\n");
s.Append("// -->\n");
s.Append("</SCRIPT>");
// Register Client Script
if (!control.Page.IsClientScriptBlockRegistered("InitialFocus"))
control.Page.RegisterClientScriptBlock("InitialFocus",
s.ToString());
}
}
}
}