Figure 1	Figure 2

A lot of time you come across a situation where you need to popup a new window to the users corresponding to some action on the page. In good old classic ASP days we all used to accomplish it by using window.open client side javascript method. In ASP.Net the method is still the same but now its has gotten better. Page class has a wonderful method RegisterClientScriptBlock that does the job of emitting client script on the page. What this method does is that it emits all the text that you specify as the second parameter to this method on the page right after opening <form> tag. Therefore the script gets executed right after the opening tags. Therefore it is important that you don't put any code that requires access to any variables that will be generated toward the end of the page because they will not exist at the time of script execution.

The project attached with this article demonstrates how this concept is used on web site where a user provides his or her email address and choose to either subscribe or unsubscribe for the mailing list. When user clicks on Submit button (Figure 1), a new window is popped up with the appropriate message (Figure 2) telling the user about their action. On pop window message we use RegisterClientScriptBlock method to register client-side script that will close the windows when user clicks on Close button (Figure 2).

Folowing code is used to pop-up new window

private void OnSubmit(object sender, System.EventArgs e)
{
	string strQS = "NotifySubscriber.aspx?email=";
	strQS += Email_TextBox.Text;
	strQS += "&action=";
	if (Subscribe_Radio.Checked)
	{
		strQS += "1";
	}
	else
	{
		strQS += "0";
	}

	StringBuilder strScript = new StringBuilder();
	strScript.Append("<script language=JavaScript>");
	strScript.Append("window.open('" + strQS + "', \"\",\"height=100,width=400,left=0,top=0,toolbar=no,menubar=no\");");
	strScript.Append("</script>");
	RegisterClientScriptBlock("subscribescript", strScript.ToString());
}						
						

Notice that we have included the opening and closing <script> tags in the the script. This is very important otherwise the script text will be displayed on the page as such and it will not be executed.