RequiredFieldValidator.EvaluateIsValid-Methode
Wird während der Validierungsphase aufgerufen, wenn ASP.NET ein Web Form verarbeitet.
Namespace: System.Web.UI.WebControls
Assembly: System.Web (in system.web.dll)
Syntax
'Declaration
Protected Overrides Function EvaluateIsValid As Boolean
'Usage
Dim returnValue As Boolean
returnValue = Me.EvaluateIsValid
protected override bool EvaluateIsValid ()
protected:
virtual bool EvaluateIsValid () override
protected boolean EvaluateIsValid ()
protected override function EvaluateIsValid () : boolean
Rückgabewert
true, wenn der Wert im Eingabesteuerelement gültig ist, andernfalls false.
Beispiel
Im folgenden Codebeispiel wird veranschaulicht, wie die EvaluateIsValid-Methode in einem benutzerdefinierten Serversteuerelement überschrieben wird, sodass sie immer false zurückgibt, wenn der Wert des RequiredFieldValidator NULL oder leer ist, und andernfalls immer true zurückgegeben wird.
<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.VB.Controls" Assembly="Samples.AspNet.VB" %>
<%@ Page Language="VB" AutoEventWireup="True" %>
<HTML>
<HEAD>
<title>Custom RequiredFieldValidator - EvaluateIsValid - VB.NET Example</title>
<script runat="server">
Sub Button1_Click(sender As Object, e As EventArgs)
If Page.IsValid Then
Label1.Text = "Required field is filled!"
Else
Label1.Text = "Required field is empty!"
End If
End Sub
</script>
</HEAD>
<body>
<form id="Form1" method="post" runat="server">
<h3>Custom RequiredFieldValidator - EvaluateIsValid - VB.NET Example</h3>
<table border="0" cellpadding="4" cellspacing="0">
<tr valign="top">
<td colspan="3">
<asp:Label ID="Label1" runat="server"
Text="Fill in the required field below" />
</td>
</tr>
<tr>
<td align="right">Card Number:</td>
<td>
<asp:TextBox id="TextBox1" runat="server" />
</td>
<td>
<aspSample:CustomRequiredFieldValidatorEvaluateIsValid id="RequiredFieldValidator1"
runat="server" ControlToValidate="TextBox1" Display="Static" ErrorMessage="*" />
</td>
</tr>
<tr>
<td> </td>
<td>
<asp:Button id="Button1" runat="server" Text="Validate"
OnClick="Button1_Click" />
</td>
<td> </td>
</tr>
</table>
</form>
</body>
</HTML>
...
Imports System.Web
Imports System.Security.Permissions
Namespace Samples.AspNet.VB.Controls
<AspNetHostingPermission(SecurityAction.Demand, Level:=AspNetHostingPermissionLevel.Minimal)> _
Public NotInheritable Class CustomRequiredFieldValidatorEvaluateIsValid
Inherits System.Web.UI.WebControls.RequiredFieldValidator
Protected Overrides Function EvaluateIsValid() As Boolean
' Get the ControlToValidate's value.
Dim controlValue As String = GetControlValidationValue(ControlToValidate)
' If ControlToValidate's value is null or empty, then return false.
If controlValue Is Nothing OrElse controlValue.Trim().Equals(System.String.Empty) Then
Return False
Else ' Else the control contains a value so return true.
Return True
End If
End Function
End Class
End Namespace
<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.CS.Controls" Assembly="Samples.AspNet.CS" %>
<%@ Page Language="C#" AutoEventWireup="True" %>
<HTML>
<HEAD>
<title>Custom RequiredFieldValidator - EvaluateIsValid - C# Example</title>
<script runat="server">
void Button1_Click(Object sender, EventArgs e)
{
if (Page.IsValid)
{
Label1.Text = "Required field is filled!";
}
else
{
Label1.Text = "Required field is empty!";
}
}
</script>
</HEAD>
<body>
<form id="Form1" method="post" runat="server">
<h3>Custom RequiredFieldValidator - EvaluateIsValid - C# Example</h3>
<table border="0" cellpadding="4" cellspacing="0">
<tr valign="top">
<td colspan="3">
<asp:Label ID="Label1" runat="server" Text="Fill in the required field below" />
</td>
</tr>
<tr>
<td align="right">Card Number:</td>
<td>
<asp:TextBox id="TextBox1" runat="server" />
</td>
<td>
<aspSample:CustomRequiredFieldValidatorEvaluateIsValid
id="RequiredFieldValidator1"
runat="server"
ControlToValidate="TextBox1"
Display="Static"
ErrorMessage="*" />
</td>
</tr>
<tr>
<td> </td>
<td>
<asp:Button
id="Button1"
runat="server"
Text="Validate"
OnClick="Button1_Click" />
</td>
<td> </td>
</tr>
</table>
</form>
</body>
</HTML>
...
using System.Web;
using System.Security.Permissions;
namespace Samples.AspNet.CS.Controls
{
[AspNetHostingPermission(SecurityAction.Demand, Level=AspNetHostingPermissionLevel.Minimal)]
public sealed class CustomRequiredFieldValidatorEvaluateIsValid : System.Web.UI.WebControls.RequiredFieldValidator
{
protected override bool EvaluateIsValid()
{
// Get the ControlToValidate's value.
string controlValue = GetControlValidationValue(ControlToValidate);
// If ControlToValidate's value is null or empty, then return false.
if ((controlValue == null) || (controlValue.Trim().Equals(System.String.Empty)))
{
return false;
}
// Else the control contains a value so return true.
else
{
return true;
}
}
}
}
<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.JSL.Controls" Assembly="Samples.AspNet.JSL" %>
<%@ Page Language="VJ#" AutoEventWireup="True" %>
<HTML>
<HEAD>
<title>Custom RequiredFieldValidator - EvaluateIsValid - VJ# Example</title>
<script runat="server">
void Button1_Click(Object sender, EventArgs e)
{
if (get_Page().get_IsValid()) {
Label1.set_Text("Required field is filled!");
}
else {
Label1.set_Text("Required field is empty!");
}
} //Button1_Click
</script>
</HEAD>
<body>
<form id="Form1" method="post" runat="server">
<h3>Custom RequiredFieldValidator - EvaluateIsValid - VJ# Example</h3>
<table border="0" cellpadding="4" cellspacing="0">
<tr valign="top">
<td colspan="3">
<asp:Label ID="Label1" runat="server" Text="Fill in the required field below" />
</td>
</tr>
<tr>
<td align="right">Card Number:</td>
<td>
<asp:TextBox id="TextBox1" runat="server" />
</td>
<td>
<aspSample:CustomRequiredFieldValidatorEvaluateIsValid
id="RequiredFieldValidator1"
runat="server"
ControlToValidate="TextBox1"
Display="Static"
ErrorMessage="*" />
</td>
</tr>
<tr>
<td> </td>
<td>
<asp:Button
id="Button1"
runat="server"
Text="Validate"
OnClick="Button1_Click" />
</td>
<td> </td>
</tr>
</table>
</form>
</body>
</HTML>
...
package Samples.AspNet.JSL.Controls;
public class CustomRequiredFieldValidatorEvaluateIsValid
extends System.Web.UI.WebControls.RequiredFieldValidator
{
protected boolean EvaluateIsValid()
{
// Get the ControlToValidate's value.
String controlValue = GetControlValidationValue(get_ControlToValidate());
// If ControlToValidate's value is null or empty, then return false.
if (controlValue == null || controlValue.Trim().Equals("")) {
return false;
}
// Else the control contains a value so return true.
else {
return true;
}
} //EvaluateIsValid
} //CustomRequiredFieldValidatorEvaluateIsValid
Plattformen
Windows 98, Windows 2000 SP4, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
.NET Framework unterstützt nicht alle Versionen sämtlicher Plattformen. Eine Liste der unterstützten Versionen finden Sie unter Systemanforderungen.
Versionsinformationen
.NET Framework
Unterstützt in: 2.0, 1.1, 1.0
Siehe auch
Referenz
RequiredFieldValidator-Klasse
RequiredFieldValidator-Member
System.Web.UI.WebControls-Namespace