CustomValidator.EvaluateIsValid Method
.NET Framework 4
This API supports the .NET Framework infrastructure and is not intended to be used directly from your code.
Overrides the BaseValidator.EvaluateIsValid method.
Assembly: System.Web (in System.Web.dll)
The following code example demonstrates how to override the EvaluateIsValid method in a custom server control.
Security Note
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This example has a text box that accepts user input, which is a potential security threat. By default, ASP.NET Web pages validate that user input does not include script or HTML elements. For more information, see Script Exploits Overview. |
<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.CS.Controls" Assembly="Samples.AspNet.CS" %> <%@ Page Language="C#" AutoEventWireup="True" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" > <head> <title>Custom CustomValidator - EvaluateIsValid - C# Example</title> </head> <body> <form id="Form1" method="post" runat="server"> <h3>Custom CustomValidator - EvaluateIsValid - C# Example</h3> <asp:Label id="Label1" runat="server" Text="Enter an even number:" AssociatedControlID="TextBox1" /><br /> <asp:TextBox id="TextBox1" runat="server" /> <aspSample:CustomCustomValidatorEvaluateIsValid id="Customvalidator1" runat="server" ControlToValidate="TextBox1" Display="Static" ErrorMessage="Not an even number!" /><br /><br /> <asp:Button id="Button1" runat="server" Text="Validate" /> </form> </body> </html> ... using System.Web; using System.Security.Permissions; namespace Samples.AspNet.CS.Controls { [AspNetHostingPermission(SecurityAction.Demand, Level = AspNetHostingPermissionLevel.Minimal)] public sealed class CustomCustomValidatorEvaluateIsValid : System.Web.UI.WebControls.CustomValidator { protected override bool EvaluateIsValid() { bool isValid = false; // Get the name of the control to validate. string controlToValidate = this.ControlToValidate; if (controlToValidate.Length > 0) { // Get the control's value. string controlValue = GetControlValidationValue(controlToValidate); // If the value is not null and not empty, test whether // check if the value entered into the text box is even, // if so return true, else return false in all other cases. if ((controlValue != null) && (!controlValue.Trim().Equals(System.String.Empty))) { try { int i = int.Parse(controlValue); isValid = ((i%2) == 0); } catch {} } } return isValid; } } }
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
