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ASP.NET Tutorial/Validation/RequiredFieldValidator - История изменений
2026-04-29T21:33:01Z
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http://nfex.ru/index.php?title=ASP.NET_Tutorial/Validation/RequiredFieldValidator&diff=3039&oldid=prev
в 15:30, 26 мая 2010
2010-05-26T15:30:57Z
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http://nfex.ru/index.php?title=ASP.NET_Tutorial/Validation/RequiredFieldValidator&diff=3040&oldid=prev
Admin: 1 версия
2010-05-26T11:57:48Z
<p>1 версия</p>
<p><b>Новая страница</b></p><div>== A simple use of the RequiredFieldValidator server control (C#)==<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="csharp"><br />
<%@ Page Language="C#" %><br />
<script runat="server"><br />
protected void Button1_Click(Object sender, EventArgs e) {<br />
Label1.Text = "Page is valid!";<br />
}<br />
</script><br />
<html xmlns="http://www.w3.org/1999/xhtml" ><br />
<head id="Head1" runat="server"><br />
<title>RequiredFieldValidator</title><br />
</head><br />
<body><br />
<form id="form1" runat="server"><br />
<div><br />
<asp:TextBox ID="TextBox1" Runat="server"></asp:TextBox><br />
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" <br />
Runat="server" <br />
ErrorMessage="Required!" <br />
ControlToValidate="TextBox1"><br />
</asp:RequiredFieldValidator><br />
<asp:Button ID="Button1" <br />
Runat="server" <br />
Text="Submit" <br />
OnClick="Button1_Click" /><br />
<asp:Label ID="Label1" Runat="server"></asp:Label> <br />
</div><br />
</form><br />
</body><br />
</html></source><br />
<br />
<br />
<br />
== asp:RequiredFieldValidator will be converted to JavaScript Code after loading in client side==<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="csharp"><br />
<%@ Page Language="VB" AutoEventWireup="false" CodeFile="Default.aspx.vb" Inherits="MyPage" %><br />
<html xmlns="http://www.w3.org/1999/xhtml" ><br />
<head runat="server"><br />
<title>Untitled Page</title><br />
</head><br />
<body><br />
<form id="form1" runat="server"><br />
<div><br />
Your name:<br />
<asp:TextBox ID="name" runat="server"></asp:TextBox><br />
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ControlToValidate="name"<br />
ErrorMessage="You must provide your name."></asp:RequiredFieldValidator><br /><br />
<br /><br />
<asp:Button ID="btnSubmit" runat="server" Text="Click Me" /><br />
<br /><br />
<br /><br />
<asp:Label ID="results" runat="server"></asp:Label></div><br />
</form><br />
</body><br />
</html><br />
File: Default.aspx.vb<br />
<br />
Partial Class MyPage<br />
Inherits System.Web.UI.Page<br />
Protected Sub btnSubmit_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnSubmit.Click<br />
If Page.IsValid Then<br />
results.Text = "Input is valid..."<br />
Else<br />
results.Text = "Input is <b>not</b> valid..."<br />
End If<br />
End Sub<br />
End Class</source><br />
<br />
<br />
<br />
== Disabling client-side validations in a validation control==<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="csharp"><br />
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" Runat="server"<br />
ErrorMessage="*" ControlToValidate="TextBox1" EnableClientScript="false"></source><br />
<br />
<br />
<br />
== EnableClientScript=false, Display=Static==<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="csharp"><br />
<%@ Page Language="C#" %><br />
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><br />
<html xmlns="http://www.w3.org/1999/xhtml"><br />
<head runat="server"><br />
<title>Sample Validation Tester</title><br />
</head><br />
<body><br />
<form id="form1" runat="server"><br />
<div><br />
User<br />
<asp:TextBox ID="txtUserName" runat="server" /><br />
<asp:RequiredFieldValidator ID="reqUser" <br />
runat="server" <br />
ControlToValidate="txtUserName"<br />
EnableClientScript="false" <br />
Display="Static"<br />
Text="Please enter a User Name" /><br />
<br /><br />
<asp:Button ID="btnTest" runat="server" Text="submit" /><br />
<br /><br />
</div><br />
</form><br />
</body><br />
</html></source><br />
<br />
<br />
<br />
== Hard code error message==<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="csharp"><br />
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="Login" %><br />
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><br />
<html xmlns="http://www.w3.org/1999/xhtml" ><br />
<head id="Head1" runat="server"><br />
<title>Simple Login Page</title><br />
</head><br />
<body><br />
<form id="form1" runat="server"><br />
Username:<br /><br />
<asp:TextBox id="usernameTextBox" runat="server" /><br />
<asp:RequiredFieldValidator id="usernameReq"<br />
runat="server"<br />
ControlToValidate="usernameTextBox"<br />
ErrorMessage="Username is required!"<br />
SetFocusOnError="True" /><br />
Password and Confirmation:<br /><br />
<asp:TextBox id="passwordTextBox" runat="server"<br />
TextMode="Password" /><br />
<asp:RequiredFieldValidator id="passwordReq"<br />
runat="server"<br />
ControlToValidate="passwordTextBox"<br />
ErrorMessage="Password is required!"<br />
SetFocusOnError="True" /><br />
<asp:TextBox id="confirmPasswordTextBox" runat="server"<br />
TextMode="Password" /><br />
<asp:RequiredFieldValidator id="confirmPasswordReq"<br />
runat="server" ControlToValidate="confirmPasswordTextBox"<br />
ErrorMessage="Password confirmation is required!"<br />
SetFocusOnError="True" /><br />
<asp:Button id="submitButton" runat="server"<br />
Text="Submit" <br />
OnClick="submitButton_Click" /><br />
</form><br />
</body><br />
</html><br />
File: Default.aspx.cs<br />
using System;<br />
using System.Data;<br />
using System.Configuration;<br />
using System.Collections;<br />
using System.Web;<br />
using System.Web.Security;<br />
using System.Web.UI;<br />
using System.Web.UI.WebControls;<br />
using System.Web.UI.WebControls.WebParts;<br />
using System.Web.UI.HtmlControls;<br />
public partial class Login : System.Web.UI.Page<br />
{<br />
protected void submitButton_Click(object sender, EventArgs e)<br />
{<br />
if (Page.IsValid)<br />
{<br />
submitButton.Text = "Valid";<br />
}<br />
else<br />
{<br />
submitButton.Text = "Invalid!";<br />
}<br />
}<br />
}</source><br />
<br />
<br />
<br />
== Placing values between nodes==<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="csharp"><br />
<%@ Page Language="VB" %><br />
<script runat="server"><br />
Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs)<br />
Label1.Text = "Page is valid!"<br />
End Sub<br />
</script><br />
<html xmlns="http://www.w3.org/1999/xhtml" ><br />
<head id="Head1" runat="server"><br />
<title>RequiredFieldValidator</title><br />
</head><br />
<body><br />
<form id="form1" runat="server"><br />
<div><br />
<asp:TextBox ID="TextBox1" Runat="server"></asp:TextBox><br />
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" <br />
Runat="server" <br />
ControlToValidate="TextBox1"><br />
Required!<br />
</asp:RequiredFieldValidator><br />
<br /><br />
<asp:Button ID="Button1" Runat="server" Text="Submit" <br />
OnClick="Button1_Click" /><br />
<br /><br />
<br /><br />
<asp:Label ID="Label1" Runat="server"></asp:Label> <br />
</div><br />
</form><br />
</body><br />
</html></source><br />
<br />
<br />
<br />
== RequiredFieldValidator Dynamic Display==<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="csharp"><br />
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="Login" %><br />
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><br />
<html xmlns="http://www.w3.org/1999/xhtml" ><br />
<head id="Head1" runat="server"><br />
<title>Simple Login Page</title><br />
</head><br />
<body><br />
<form id="form1" runat="server"><br />
Username:<br />
<asp:TextBox id="usernameTextBox" runat="server" /><br />
<asp:RequiredFieldValidator id="usernameReq"<br />
runat="server"<br />
ControlToValidate="usernameTextBox"<br />
ErrorMessage="Username is required!"<br />
SetFocusOnError="True" /><br />
Password and Confirmation:<br /><br />
<asp:TextBox id="passwordTextBox" runat="server"<br />
TextMode="Password" /><br />
<asp:RequiredFieldValidator id="passwordReq"<br />
runat="server"<br />
ControlToValidate="passwordTextBox"<br />
ErrorMessage="Password is required!"<br />
SetFocusOnError="True" <br />
Display="Dynamic" /><br />
<asp:TextBox id="confirmPasswordTextBox" <br />
runat="server"<br />
TextMode="Password" /><br />
<asp:RequiredFieldValidator id="confirmPasswordReq"<br />
runat="server" <br />
ControlToValidate="confirmPasswordTextBox"<br />
ErrorMessage="Password confirmation is required!"<br />
SetFocusOnError="True" <br />
Display="Dynamic" /><br />
<asp:Button id="submitButton" <br />
runat="server"<br />
Text="Submit" <br />
OnClick="submitButton_Click" /><br />
</div><br />
</form><br />
</body><br />
</html><br />
File: Default.aspx.cs<br />
using System;<br />
using System.Data;<br />
using System.Configuration;<br />
using System.Collections;<br />
using System.Web;<br />
using System.Web.Security;<br />
using System.Web.UI;<br />
using System.Web.UI.WebControls;<br />
using System.Web.UI.WebControls.WebParts;<br />
using System.Web.UI.HtmlControls;<br />
public partial class Login : System.Web.UI.Page<br />
{<br />
protected void submitButton_Click(object sender, EventArgs e)<br />
{<br />
if (Page.IsValid)<br />
{<br />
submitButton.Text = "Valid";<br />
}<br />
else<br />
{<br />
submitButton.Text = "Invalid!";<br />
}<br />
}<br />
}</source><br />
<br />
<br />
<br />
== RequiredFieldValidator for login page==<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="csharp"><br />
<%@ Page Language="C#" %><br />
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><br />
<html xmlns="http://www.w3.org/1999/xhtml" ><br />
<head id="Head1" runat="server"><br />
<title>Simple Login Page</title><br />
</head><br />
<body><br />
<form id="form1" runat="server"><br />
Username:<br />
<asp:TextBox id="usernameTextBox" runat="server" /><br />
<asp:RequiredFieldValidator id="usernameReq"<br />
runat="server"<br />
ControlToValidate="usernameTextBox"<br />
ErrorMessage="Username is required!"<br />
SetFocusOnError="True" /><br />
Password:<br /><br />
<asp:TextBox id="passwordTextBox" <br />
runat="server"<br />
TextMode="Password" /><br />
<asp:RequiredFieldValidator id="passwordReq"<br />
runat="server"<br />
ControlToValidate="passwordTextBox"<br />
ErrorMessage="Password is required!"<br />
SetFocusOnError="True" /><br />
<asp:Button id="submitButton" runat="server"<br />
Text="Submit" /><br />
</form><br />
</body><br />
</html></source><br />
<br />
<br />
<br />
== RequiredFieldValidator requires a user to enter a value into a form field before submitting the form.==<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="csharp"><br />
Two important properties when using the RequiredFieldValdiator control:<br />
ControlToValidate: The ID of the form field being validated.<br />
Text: The error message.<br />
<%@ Page Language="C#" %><br />
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"<br />
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><br />
<html xmlns="http://www.w3.org/1999/xhtml" ><br />
<head id="Head1" runat="server"><br />
<title>Show RequiredFieldValidator</title><br />
</head><br />
<body><br />
<form id="form1" runat="server"><br />
<div><br />
<asp:Label<br />
id="lblFirstName"<br />
Text="First Name:"<br />
AssociatedControlID="txtFirstName"<br />
Runat="server" /><br />
<asp:TextBox<br />
id="txtFirstName"<br />
Runat="server" /><br />
<asp:RequiredFieldValidator<br />
id="reqFirstName"<br />
ControlToValidate="txtFirstName"<br />
Text="(Required)"<br />
Runat="server" /><br />
<asp:Label<br />
id="lblLastName"<br />
Text="Last Name:"<br />
AssociatedControlID="txtLastName"<br />
Runat="server" /><br />
<br /><br />
<asp:TextBox<br />
id="txtLastName"<br />
Runat="server" /><br />
<asp:RequiredFieldValidator<br />
id="reqLastName"<br />
ControlToValidate="txtLastName"<br />
Text="(Required)"<br />
Runat="server" /><br />
<asp:Button<br />
id="btnSubmit"<br />
Text="Submit"<br />
Runat="server" /><br />
</div><br />
</form><br />
</body><br />
</html></source><br />
<br />
<br />
<br />
== RequiredFieldValidator with server side validation==<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="csharp"><br />
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="Login" %><br />
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><br />
<html xmlns="http://www.w3.org/1999/xhtml" ><br />
<head id="Head1" runat="server"><br />
<title>Simple Login Page</title><br />
</head><br />
<body><br />
<form id="form1" runat="server"><br />
Username:<br /><br />
<asp:TextBox id="usernameTextBox" runat="server" /><br />
<asp:RequiredFieldValidator id="usernameReq"<br />
runat="server"<br />
ControlToValidate="usernameTextBox"<br />
ErrorMessage="Username is required!"<br />
SetFocusOnError="True" /><br />
Password:<br /><br />
<asp:TextBox id="passwordTextBox" <br />
runat="server"<br />
TextMode="Password" /><br />
<asp:RequiredFieldValidator id="passwordReq"<br />
runat="server"<br />
ControlToValidate="passwordTextBox"<br />
ErrorMessage="Password is required!"<br />
SetFocusOnError="True" /><br />
<asp:Button id="submitButton" <br />
runat="server"<br />
Text="Submit" <br />
OnClick="submitButton_Click" /><br />
</form><br />
</body><br />
</html><br />
File: Default.aspx.cs<br />
using System;<br />
using System.Data;<br />
using System.Configuration;<br />
using System.Collections;<br />
using System.Web;<br />
using System.Web.Security;<br />
using System.Web.UI;<br />
using System.Web.UI.WebControls;<br />
using System.Web.UI.WebControls.WebParts;<br />
using System.Web.UI.HtmlControls;<br />
public partial class Login : System.Web.UI.Page<br />
{<br />
protected void submitButton_Click(object sender, EventArgs e)<br />
{<br />
if (Page.IsValid)<br />
{<br />
submitButton.Text = "Valid";<br />
}<br />
else<br />
{<br />
submitButton.Text = "Invalid!";<br />
}<br />
}<br />
}</source><br />
<br />
<br />
<br />
== Specify ErrorMessage for asp:RequiredFieldValidator==<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="csharp"><br />
<%@ Page Language="VB" AutoEventWireup="false" %><br />
<html xmlns="http://www.w3.org/1999/xhtml" ><br />
<head runat="server"><br />
<title>Untitled Page</title><br />
</head><br />
<body><br />
<form id="form1" runat="server"><br />
<div><br />
<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox><br />
<asp:RequiredFieldValidator <br />
ID="RequiredFieldValidator1" <br />
runat="server" <br />
ControlToValidate="TextBox1"<br />
ErrorMessage="error"></asp:RequiredFieldValidator><br />
This text appears right after a textbox.<br />
<br /><br />
<br /><br />
<asp:TextBox ID="TextBox2" runat="server"></asp:TextBox><br />
<asp:RequiredFieldValidator ID="RequiredFieldValidator2" runat="server" ControlToValidate="TextBox2"<br />
Display="Dynamic" ErrorMessage="error"></asp:RequiredFieldValidator><br />
This text appears right after a textbox.<br />
<br /><br />
<br /><br />
<asp:Button ID="Button1" runat="server" Text="Button" /></div><br />
</form><br />
</body><br />
</html></source><br />
<br />
<br />
<br />
== Text field of RequiredFieldValidator server control (VB)==<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="csharp"><br />
<%@ Page Language="VB" %><br />
<script runat="server"><br />
Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs)<br />
Label1.Text = "Page is valid!"<br />
End Sub<br />
</script><br />
<html xmlns="http://www.w3.org/1999/xhtml" ><br />
<head id="Head1" runat="server"><br />
<title>RequiredFieldValidator</title><br />
</head><br />
<body><br />
<form id="form1" runat="server"><br />
<div><br />
<asp:TextBox ID="TextBox1" Runat="server"></asp:TextBox><br />
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" <br />
Runat="server" <br />
Text="Required!"<br />
ErrorMessage="Required!" <br />
ControlToValidate="TextBox1"><br />
</asp:RequiredFieldValidator><br />
<br /><br />
<asp:Button ID="Button1" Runat="server" Text="Submit" <br />
OnClick="Button1_Click" /><br />
<br /><br />
<br /><br />
<asp:Label ID="Label1" Runat="server"></asp:Label> <br />
</div><br />
</form><br />
</body><br />
</html></source><br />
<br />
<br />
<br />
== Use asp:RequiredFieldValidator to check the input of an asp:TextBox (VB.net)==<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="csharp"><br />
<%@ Page Language="VB" %><br />
<script runat="server"><br />
sub Submit(Sender as Object, e as EventArgs)<br />
if Page.IsValid then<br />
lblMessage.Text = "You passed validation!"<br />
end if <br />
end sub<br />
</script><br />
<html><br />
<body><br />
<form runat="server"><br />
<asp:Label id="lblMessage" runat="server" /><br />
Enter your name:<br />
<asp:TextBox id="tbFName" runat="server" /><br><br />
<asp:RequiredFieldValidator runat="server" ControlToValidate="tbFName" ErrorMessage="First name required"/><br />
<asp:Button id="tbSubmit" runat="server" Text="Submit" OnClick="Submit" /><br />
</form><br />
</body><br />
</html></source><br />
<br />
<br />
<br />
== Use the RequiredFieldValidator"s InitialValue to set a default value==<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="csharp"><br />
<%@ Page Language="C#" %><br />
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"<br />
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><br />
<script runat="server"><br />
void btnSubmit_Click(Object sender, EventArgs e)<br />
{<br />
if (Page.IsValid)<br />
lblResult.Text = dropFavoriteColor.SelectedValue;<br />
}<br />
</script><br />
<html xmlns="http://www.w3.org/1999/xhtml" ><br />
<head id="Head1" runat="server"><br />
<title>Show Initial Value</title><br />
</head><br />
<body><br />
<form id="form1" runat="server"><br />
<div><br />
<asp:Label<br />
id="lblFavoriteColor"<br />
Text="Favorite Color:"<br />
AssociatedControlID="dropFavoriteColor"<br />
Runat="server" /><br />
<br /><br />
<asp:DropDownList<br />
id="dropFavoriteColor"<br />
Runat="server"><br />
<asp:ListItem Text="Select Color" Value="none" /><br />
<asp:ListItem Text="Red" Value="Red" /><br />
<asp:ListItem Text="Blue" Value="Blue" /><br />
<asp:ListItem Text="Green" Value="Green" /><br />
</asp:DropDownList><br />
<asp:RequiredFieldValidator<br />
id="reqFavoriteColor"<br />
Text="(Required)"<br />
InitialValue="none"<br />
ControlToValidate="dropFavoriteColor"<br />
Runat="server" /><br />
<asp:Button<br />
id="btnSubmit"<br />
Text="Submit"<br />
Runat="server" OnClick="btnSubmit_Click" /><br />
<asp:Label<br />
id="lblResult"<br />
Runat="server" /><br />
</div><br />
</form><br />
</body><br />
</html></source><br />
<br />
<br />
<br />
== Using images for error notifications==<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="csharp"><br />
<asp:RequiredFieldValidator ID="RequiredFieldValidator1"<br />
Runat="server" ErrorMessage="<img src="error.gif">"<br />
ControlToValidate="TextBox1"></asp:RequiredFieldValidator></source><br />
<br />
<br />
<br />
== Using sound for error notifications==<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="csharp"><br />
<asp:RequiredFieldValidator ID="RequiredFieldValidator1"<br />
Runat="server" ErrorMessage="<bgsource src="C:\Windows\Media\tada.wav">"<br />
ControlToValidate="TextBox1" EnableClientScript="False"><br />
</asp:RequiredFieldValidator></source><br />
<br />
<br />
<br />
== Using two RequiredFieldValidator controls for one form element==<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="csharp"><br />
<%@ Page Language="VB" %><br />
<script runat="server"><br />
Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs)<br />
Label1.Text = "Page is valid!"<br />
End Sub<br />
</script><br />
<html xmlns="http://www.w3.org/1999/xhtml" ><br />
<head id="Head1" runat="server"><br />
<title>RequiredFieldValidator</title><br />
</head><br />
<body><br />
<form id="form1" runat="server"><br />
<div><br />
<asp:TextBox ID="TextBox1" Runat="server">My Initial Value</asp:TextBox>&nbsp;<br />
<br />
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" <br />
Runat="server" <br />
ErrorMessage="Please change value" <br />
ControlToValidate="TextBox1"<br />
InitialValue="My Initial Value"/><br />
<asp:RequiredFieldValidator ID="RequiredFieldValidator2" <br />
Runat="server"<br />
ErrorMessage="Do not leave empty" <br />
ControlToValidate="TextBox1"><br />
</asp:RequiredFieldValidator><br />
<br /><br />
<asp:Button ID="Button1" Runat="server" Text="Submit" <br />
OnClick="Button1_Click" /><br />
<br /><br />
<br /><br />
<asp:Label ID="Label1" Runat="server"></asp:Label> <br />
</div><br />
</form><br />
</body><br />
</html></source><br />
<br />
<br />
<br />
== Validating Drop-Down Lists with the RequiredFieldValidator Control==<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="csharp"><br />
<%@ Page Language="VB" %><br />
<script runat="server"><br />
Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs)<br />
Label1.Text = "Page is valid!"<br />
End Sub<br />
</script><br />
<html xmlns="http://www.w3.org/1999/xhtml" ><br />
<head id="Head1" runat="server"><br />
<title>RequiredFieldValidator</title><br />
</head><br />
<body><br />
<form id="form1" runat="server"><br />
<div><br />
<asp:DropDownList id="DropDownList1" runat="server"><br />
<asp:ListItem Selected="True">Select a profession</asp:ListItem><br />
<asp:ListItem>Programmer</asp:ListItem><br />
<asp:ListItem>Lawyer</asp:ListItem><br />
<asp:ListItem>Doctor</asp:ListItem><br />
<asp:ListItem>Artist</asp:ListItem><br />
</asp:DropDownList><br />
<asp:RequiredFieldValidator id="RequiredFieldValidator1" <br />
runat="server" <br />
ErrorMessage="Please make a selection"<br />
ControlToValidate="DropDownList1"<br />
InitialValue="Select a profession"><br />
</asp:RequiredFieldValidator><br />
<br /><br />
<asp:Button ID="Button1" Runat="server" Text="Submit" <br />
OnClick="Button1_Click" /><br />
<br /><br />
<br /><br />
<asp:Label ID="Label1" Runat="server"></asp:Label> <br />
</div><br />
</form><br />
</body><br />
</html></source><br />
<br />
<br />
<br />
== Working with the InitialValue property==<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="csharp"><br />
<%@ Page Language="VB" %><br />
<script runat="server"><br />
Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs)<br />
Label1.Text = "Page is valid!"<br />
End Sub<br />
</script><br />
<html xmlns="http://www.w3.org/1999/xhtml" ><br />
<head id="Head1" runat="server"><br />
<title>RequiredFieldValidator</title><br />
</head><br />
<body><br />
<form id="form1" runat="server"><br />
<div><br />
<asp:TextBox ID="TextBox1" Runat="server">My Initial Value</asp:TextBox><br />
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" <br />
Runat="server" <br />
ErrorMessage="Please change the value of the textbox!" <br />
ControlToValidate="TextBox1" <br />
InitialValue="My Initial Value"><br />
</asp:RequiredFieldValidator><br />
<br /><br />
<asp:Button ID="Button1" Runat="server" Text="Submit" <br />
OnClick="Button1_Click" /><br />
<br /><br />
<br /><br />
<asp:Label ID="Label1" Runat="server"></asp:Label> <br />
</div><br />
</form><br />
</body><br />
</html></source></div>
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