Validate user input in Windows Forms

///////////////////////////////////////////////////////////
// File:			Validation.js
// File Start Date:	July 30, 2002
// Description:		Routes validation to appropriate validation handler
//
// This file must be placed in to /inetpub/wwwroot/_vti_script

String.prototype.trim = function()
{
	return this.replace(/^\s*(\b.*\b|)\s*$/, "$1");
}

String.prototype.isDate = function()
{
	var re=/^((0?\d)|(1[0-2]))(\\|\/|-)((0?\d)|([1-2]\d)|(3[0-1]))(\\|\/|-)(\d{2}|\d{4})$/;
	return re.test(this);
}

String.prototype.isTime = function()
{
	var re=/^(((0?[1-9]|1[0-2])(:|\.)[0-5]\d((:|\.)[0-5]\d)?( )?(([aA]|[pP])[mM]))|((0?\d|1\d|2[0-3])(:|\.)[0-5]\d((:|\.)[0-5]\d)?))$/;
	return re.test(this);
}

String.prototype.isDateTime = function()
{
	var re=/^((0?\d)|(1[0-2]))(\\|\/|-)((0?\d)|([1-2]\d)|(3[0-1]))(\\|\/|-)(\d{2}|\d{4})( )(((0?[1-9]|1[0-2])(:|\.)[0-5]\d((:|\.)[0-5]\d)?( )?(([aA]|[pP])[mM]))|((0?\d|1\d|2[0-3])(:|\.)[0-5]\d((:|\.)[0-5]\d)?))$/;
	
	if (this.isDate()) return true;
	if (this.isTime()) return true;
	if (re.test(this)) return true;
	return false;
}

Array.prototype.indexOf = function(val)
{
	for (var i=0; i<this.length; i++)
		if (this[i]==val) return i;
	return -1;
}

function IsInteger(val)
{
	if (val=='') return true;
	if (isNaN(parseFloat(val))) return false;
	if (parseInt(val) < parseFloat(val)) return false;
	if (val.lastIndexOf(".")==val.length-1) return false;
	return true;
}

function IsDouble(val)
{
	if (val=='') return true;
	if (isNaN(parseFloat(val))) return false;
	if (val.lastIndexOf(".")==val.length-1) return false;
	return true;
}

if (document.getElementById) //DOM Compliant browser
	document.write("<script language=\"javascript\" src=\"/_vti_script/ValidationDOM.js\"></script>");
else if (document.all) //Non-DOM Compliant IE
	document.write("<script language=\"javascript\" src=\"/_vti_script/ValidationIE.js\"></script>");
else
{
	//Force server side validation for other browsers
	document.write("<script language=\"javascript\">");
	document.write("function ClientValidation(val){return true;}");
	document.write("</script>");
}