ASP.NET Tutorial/Validation/RequiredFieldValidator

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A simple use of the RequiredFieldValidator server control (C#)

   <source lang="csharp">

<%@ Page Language="C#" %> <script runat="server"> 

   protected void Button1_Click(Object sender, EventArgs e) {
      Label1.Text = "Page is valid!";
   }

</script> <html xmlns="http://www.w3.org/1999/xhtml" > <head id="Head1" runat="server"> 

   <title>RequiredFieldValidator</title>

</head> <body> 

   <form id="form1" runat="server">

       <asp:TextBox ID="TextBox1" Runat="server"></asp:TextBox>
       <asp:RequiredFieldValidator ID="RequiredFieldValidator1" 
                                   Runat="server" 
                                   ErrorMessage="Required!" 
                                   ControlToValidate="TextBox1">
       </asp:RequiredFieldValidator>
       <asp:Button ID="Button1" 
        Runat="server" 
        Text="Submit" 
        OnClick="Button1_Click" />
       <asp:Label ID="Label1" Runat="server"></asp:Label>    

   </form>

</body> </html></source>


asp:RequiredFieldValidator will be converted to JavaScript Code after loading in client side

   <source lang="csharp">

<%@ Page Language="VB" AutoEventWireup="false" CodeFile="Default.aspx.vb" Inherits="MyPage" %> <html xmlns="http://www.w3.org/1999/xhtml" > <head runat="server"> 

   <title>Untitled Page</title>

</head> <body> 

   <form id="form1" runat="server">

       Your name:
       <asp:TextBox ID="name" runat="server"></asp:TextBox>
       <asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ControlToValidate="name"
           ErrorMessage="You must provide your name."></asp:RequiredFieldValidator>

       

       <asp:Button ID="btnSubmit" runat="server" Text="Click Me" />
<asp:Label ID="results" runat="server"></asp:Label>
   </form>

</body> </html> File: Default.aspx.vb

Partial Class MyPage 

   Inherits System.Web.UI.Page
   Protected Sub btnSubmit_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnSubmit.Click
       If Page.IsValid Then
           results.Text = "Input is valid..."
       Else
           results.Text = "Input is not valid..."
       End If
   End Sub

End Class</source>


Disabling client-side validations in a validation control

   <source lang="csharp">

<asp:RequiredFieldValidator ID="RequiredFieldValidator1" Runat="server" 

 ErrorMessage="*" ControlToValidate="TextBox1" EnableClientScript="false"></source>

EnableClientScript=false, Display=Static

   <source lang="csharp">

<%@ Page Language="C#" %> <!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 runat="server"> 

  <title>Sample Validation Tester</title>

</head> <body> 

  <form id="form1" runat="server">

        User
        <asp:TextBox ID="txtUserName" runat="server" />
        <asp:RequiredFieldValidator ID="reqUser" 
           runat="server" 
           ControlToValidate="txtUserName"
           EnableClientScript="false" 
           Display="Static"
           Text="Please enter a User Name" />
        

        <asp:Button ID="btnTest" runat="server" Text="submit" />
        


  </form>

</body> </html></source>


Hard code error message

   <source lang="csharp">

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="Login" %> <!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 id="Head1" runat="server"> 

   <title>Simple Login Page</title>

</head> <body> 

   <form id="form1" runat="server">
   Username:

         <asp:TextBox id="usernameTextBox" runat="server" />
         <asp:RequiredFieldValidator id="usernameReq"
             runat="server"
             ControlToValidate="usernameTextBox"
             ErrorMessage="Username is required!"
             SetFocusOnError="True" />
   Password and Confirmation:

         <asp:TextBox id="passwordTextBox" runat="server"
             TextMode="Password" />
         <asp:RequiredFieldValidator id="passwordReq"
             runat="server"
             ControlToValidate="passwordTextBox"
             ErrorMessage="Password is required!"
             SetFocusOnError="True" />
         <asp:TextBox id="confirmPasswordTextBox" runat="server"
             TextMode="Password" />
         <asp:RequiredFieldValidator id="confirmPasswordReq"
             runat="server" ControlToValidate="confirmPasswordTextBox"
             ErrorMessage="Password confirmation is required!"
             SetFocusOnError="True" />
         <asp:Button id="submitButton" runat="server"
             Text="Submit" 
             OnClick="submitButton_Click" />
   </form>

</body> </html> File: Default.aspx.cs using System; using System.Data; using System.Configuration; using System.Collections; using System.Web; using System.Web.Security; using System.Web.UI; using System.Web.UI.WebControls; using System.Web.UI.WebControls.WebParts; using System.Web.UI.HtmlControls; public partial class Login : System.Web.UI.Page { 

   protected void submitButton_Click(object sender, EventArgs e)
   {
       if (Page.IsValid)
       {
           submitButton.Text = "Valid";
       }
       else
       {
           submitButton.Text = "Invalid!";
       }
   }

}</source>


Placing values between nodes

   <source lang="csharp">

<%@ Page Language="VB" %> <script runat="server"> 

  Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs)
       Label1.Text = "Page is valid!"
  End Sub

</script> <html xmlns="http://www.w3.org/1999/xhtml" > <head id="Head1" runat="server"> 

   <title>RequiredFieldValidator</title>

</head> <body> 

   <form id="form1" runat="server">

       <asp:TextBox ID="TextBox1" Runat="server"></asp:TextBox>
       <asp:RequiredFieldValidator ID="RequiredFieldValidator1" 
                                   Runat="server" 
                                   ControlToValidate="TextBox1">
           Required!
       </asp:RequiredFieldValidator>
       

       <asp:Button ID="Button1" Runat="server" Text="Submit" 
        OnClick="Button1_Click" />
       

       

       <asp:Label ID="Label1" Runat="server"></asp:Label>    

   </form>

</body> </html></source>


RequiredFieldValidator Dynamic Display

   <source lang="csharp">

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="Login" %> <!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 id="Head1" runat="server"> 

   <title>Simple Login Page</title>

</head> <body> 

   <form id="form1" runat="server">
    Username:
         <asp:TextBox id="usernameTextBox" runat="server" />
         <asp:RequiredFieldValidator id="usernameReq"
             runat="server"
             ControlToValidate="usernameTextBox"
             ErrorMessage="Username is required!"
             SetFocusOnError="True" />
    Password and Confirmation:

         <asp:TextBox id="passwordTextBox" runat="server"
             TextMode="Password" />
         <asp:RequiredFieldValidator id="passwordReq"
             runat="server"
             ControlToValidate="passwordTextBox"
             ErrorMessage="Password is required!"
             SetFocusOnError="True" 
             Display="Dynamic" />
         <asp:TextBox id="confirmPasswordTextBox" 
             runat="server"
             TextMode="Password" />
         <asp:RequiredFieldValidator id="confirmPasswordReq"
             runat="server" 
             ControlToValidate="confirmPasswordTextBox"
             ErrorMessage="Password confirmation is required!"
             SetFocusOnError="True" 
             Display="Dynamic" />
         <asp:Button id="submitButton" 
                     runat="server"
                     Text="Submit" 
                     OnClick="submitButton_Click" />
   </div>
   </form>

</body> </html> File: Default.aspx.cs using System; using System.Data; using System.Configuration; using System.Collections; using System.Web; using System.Web.Security; using System.Web.UI; using System.Web.UI.WebControls; using System.Web.UI.WebControls.WebParts; using System.Web.UI.HtmlControls; public partial class Login : System.Web.UI.Page { 

   protected void submitButton_Click(object sender, EventArgs e)
   {
       if (Page.IsValid)
       {
           submitButton.Text = "Valid";
       }
       else
       {
           submitButton.Text = "Invalid!";
       }
   }

}</source>


RequiredFieldValidator for login page

   <source lang="csharp">

<%@ Page Language="C#" %> <!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 id="Head1" runat="server"> 

   <title>Simple Login Page</title>

</head> <body> 

   <form id="form1" runat="server">
   Username:
         <asp:TextBox id="usernameTextBox" runat="server" />
         <asp:RequiredFieldValidator id="usernameReq"
             runat="server"
             ControlToValidate="usernameTextBox"
             ErrorMessage="Username is required!"
             SetFocusOnError="True" />
   Password:

         <asp:TextBox id="passwordTextBox" 
             runat="server"
             TextMode="Password" />
         <asp:RequiredFieldValidator id="passwordReq"
             runat="server"
             ControlToValidate="passwordTextBox"
             ErrorMessage="Password is required!"
             SetFocusOnError="True" />
         <asp:Button id="submitButton" runat="server"
             Text="Submit" />
   </form>

</body> </html></source>


RequiredFieldValidator requires a user to enter a value into a form field before submitting the form.

   <source lang="csharp">

Two important properties when using the RequiredFieldValdiator control: ControlToValidate: The ID of the form field being validated. Text: The error message. <%@ Page Language="C#" %> <!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 id="Head1" runat="server"> 

   <title>Show RequiredFieldValidator</title>

</head> <body> 

   <form id="form1" runat="server">

   <asp:Label
       id="lblFirstName"
       Text="First Name:"
       AssociatedControlID="txtFirstName"
       Runat="server" />
   <asp:TextBox
       id="txtFirstName"
       Runat="server" />
   <asp:RequiredFieldValidator
       id="reqFirstName"
       ControlToValidate="txtFirstName"
       Text="(Required)"
       Runat="server" />
   <asp:Label
       id="lblLastName"
       Text="Last Name:"
       AssociatedControlID="txtLastName"
       Runat="server" />
   

   <asp:TextBox
       id="txtLastName"
       Runat="server" />
   <asp:RequiredFieldValidator
       id="reqLastName"
       ControlToValidate="txtLastName"
       Text="(Required)"
       Runat="server" />
   <asp:Button
       id="btnSubmit"
       Text="Submit"
       Runat="server" />

   </form>

</body> </html></source>


RequiredFieldValidator with server side validation

   <source lang="csharp">

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="Login" %> <!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 id="Head1" runat="server"> 

   <title>Simple Login Page</title>

</head> <body> 

   <form id="form1" runat="server">
   Username:

         <asp:TextBox id="usernameTextBox" runat="server" />
         <asp:RequiredFieldValidator id="usernameReq"
             runat="server"
             ControlToValidate="usernameTextBox"
             ErrorMessage="Username is required!"
             SetFocusOnError="True" />
   Password:

         <asp:TextBox id="passwordTextBox" 
             runat="server"
             TextMode="Password" />
         <asp:RequiredFieldValidator id="passwordReq"
             runat="server"
             ControlToValidate="passwordTextBox"
             ErrorMessage="Password is required!"
             SetFocusOnError="True" />
         <asp:Button id="submitButton" 
             runat="server"
             Text="Submit" 
             OnClick="submitButton_Click" />
   </form>

</body> </html> File: Default.aspx.cs using System; using System.Data; using System.Configuration; using System.Collections; using System.Web; using System.Web.Security; using System.Web.UI; using System.Web.UI.WebControls; using System.Web.UI.WebControls.WebParts; using System.Web.UI.HtmlControls; public partial class Login : System.Web.UI.Page { 

   protected void submitButton_Click(object sender, EventArgs e)
   {
       if (Page.IsValid)
       {
           submitButton.Text = "Valid";
       }
       else
       {
           submitButton.Text = "Invalid!";
       }
   }

}</source>


Specify ErrorMessage for asp:RequiredFieldValidator

   <source lang="csharp">

<%@ Page Language="VB" AutoEventWireup="false" %> <html xmlns="http://www.w3.org/1999/xhtml" > <head runat="server"> 

   <title>Untitled Page</title>

</head> <body> 

   <form id="form1" runat="server">

       <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
       <asp:RequiredFieldValidator 
           ID="RequiredFieldValidator1" 
           runat="server" 
           ControlToValidate="TextBox1"
           ErrorMessage="error"></asp:RequiredFieldValidator>
       This text appears right after a textbox.
       

       

       <asp:TextBox ID="TextBox2" runat="server"></asp:TextBox>
       <asp:RequiredFieldValidator ID="RequiredFieldValidator2" runat="server" ControlToValidate="TextBox2"
           Display="Dynamic" ErrorMessage="error"></asp:RequiredFieldValidator>
       This text appears right after a textbox.
<asp:Button ID="Button1" runat="server" Text="Button" />
   </form>

</body> </html></source>


Text field of RequiredFieldValidator server control (VB)

   <source lang="csharp">

<%@ Page Language="VB" %> <script runat="server"> 

  Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs)
       Label1.Text = "Page is valid!"
  End Sub

</script> <html xmlns="http://www.w3.org/1999/xhtml" > <head id="Head1" runat="server"> 

   <title>RequiredFieldValidator</title>

</head> <body> 

   <form id="form1" runat="server">

       <asp:TextBox ID="TextBox1" Runat="server"></asp:TextBox>
       <asp:RequiredFieldValidator ID="RequiredFieldValidator1" 
                                   Runat="server" 
                                   Text="Required!"
                                   ErrorMessage="Required!" 
                                   ControlToValidate="TextBox1">
       </asp:RequiredFieldValidator>
       

       <asp:Button ID="Button1" Runat="server" Text="Submit" 
        OnClick="Button1_Click" />
       

       

       <asp:Label ID="Label1" Runat="server"></asp:Label>    

   </form>

</body> </html></source>


Use asp:RequiredFieldValidator to check the input of an asp:TextBox (VB.net)

   <source lang="csharp">

<%@ Page Language="VB" %> <script runat="server"> 

  sub Submit(Sender as Object, e as EventArgs)
     if Page.IsValid then
        lblMessage.Text = "You passed validation!"
     end if   
  end sub

</script> <html> <body> 

  <form runat="server">
     <asp:Label id="lblMessage" runat="server" />
     Enter your name:
     <asp:TextBox id="tbFName" runat="server" />

     <asp:RequiredFieldValidator runat="server" ControlToValidate="tbFName" ErrorMessage="First name required"/>
     <asp:Button id="tbSubmit" runat="server" Text="Submit" OnClick="Submit" />
  </form>

</body> </html></source>


Use the RequiredFieldValidator"s InitialValue to set a default value

   <source lang="csharp">

<%@ Page Language="C#" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <script runat="server"> 

   void btnSubmit_Click(Object sender, EventArgs e)
   {
       if (Page.IsValid)
           lblResult.Text = dropFavoriteColor.SelectedValue;
   }

</script> <html xmlns="http://www.w3.org/1999/xhtml" > <head id="Head1" runat="server"> 

   <title>Show Initial Value</title>

</head> <body> 

   <form id="form1" runat="server">

   <asp:Label
       id="lblFavoriteColor"
       Text="Favorite Color:"
       AssociatedControlID="dropFavoriteColor"
       Runat="server" />
   

   <asp:DropDownList
       id="dropFavoriteColor"
       Runat="server">
       <asp:ListItem Text="Select Color" Value="none" />
       <asp:ListItem Text="Red" Value="Red" />
       <asp:ListItem Text="Blue" Value="Blue" />
       <asp:ListItem Text="Green" Value="Green" />
   </asp:DropDownList>
   <asp:RequiredFieldValidator
       id="reqFavoriteColor"
       Text="(Required)"
       InitialValue="none"
       ControlToValidate="dropFavoriteColor"
       Runat="server" />
   <asp:Button
       id="btnSubmit"
       Text="Submit"
       Runat="server" OnClick="btnSubmit_Click" />
   <asp:Label
       id="lblResult"
       Runat="server" />

   </form>

</body> </html></source>


Using images for error notifications

   <source lang="csharp">

<asp:RequiredFieldValidator ID="RequiredFieldValidator1" 

Runat="server" ErrorMessage="<img src="error.gif">"
ControlToValidate="TextBox1"></asp:RequiredFieldValidator></source>

Using sound for error notifications

   <source lang="csharp">

<asp:RequiredFieldValidator ID="RequiredFieldValidator1" 

Runat="server" ErrorMessage="<bgsource src="C:\Windows\Media\tada.wav">"
ControlToValidate="TextBox1" EnableClientScript="False">

</asp:RequiredFieldValidator></source>


Using two RequiredFieldValidator controls for one form element

   <source lang="csharp">

<%@ Page Language="VB" %> <script runat="server"> 

  Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs)
       Label1.Text = "Page is valid!"
  End Sub

</script> <html xmlns="http://www.w3.org/1999/xhtml" > <head id="Head1" runat="server"> 

   <title>RequiredFieldValidator</title>

</head> <body> 

   <form id="form1" runat="server">

       <asp:TextBox ID="TextBox1" Runat="server">My Initial Value</asp:TextBox> 
           
       <asp:RequiredFieldValidator ID="RequiredFieldValidator1" 
                                   Runat="server" 
                                   ErrorMessage="Please change value" 
                                   ControlToValidate="TextBox1"
                                   InitialValue="My Initial Value"/>
       <asp:RequiredFieldValidator ID="RequiredFieldValidator2" 
                                   Runat="server"
                                   ErrorMessage="Do not leave empty" 
                                   ControlToValidate="TextBox1">
       </asp:RequiredFieldValidator>
       

       <asp:Button ID="Button1" Runat="server" Text="Submit" 
        OnClick="Button1_Click" />
       

       

       <asp:Label ID="Label1" Runat="server"></asp:Label>    

   </form>

</body> </html></source>


Validating Drop-Down Lists with the RequiredFieldValidator Control

   <source lang="csharp">

<%@ Page Language="VB" %> <script runat="server"> 

  Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs)
       Label1.Text = "Page is valid!"
  End Sub

</script> <html xmlns="http://www.w3.org/1999/xhtml" > <head id="Head1" runat="server"> 

   <title>RequiredFieldValidator</title>

</head> <body> 

   <form id="form1" runat="server">

       <asp:DropDownList id="DropDownList1" runat="server">
          <asp:ListItem Selected="True">Select a profession</asp:ListItem>
          <asp:ListItem>Programmer</asp:ListItem>
          <asp:ListItem>Lawyer</asp:ListItem>
          <asp:ListItem>Doctor</asp:ListItem>
          <asp:ListItem>Artist</asp:ListItem>
       </asp:DropDownList>
       <asp:RequiredFieldValidator id="RequiredFieldValidator1" 
                                   runat="server" 
                                   ErrorMessage="Please make a selection"
                                   ControlToValidate="DropDownList1"
                                   InitialValue="Select a profession">
       </asp:RequiredFieldValidator>
       

       <asp:Button ID="Button1" Runat="server" Text="Submit" 
        OnClick="Button1_Click" />
       

       

       <asp:Label ID="Label1" Runat="server"></asp:Label>    

   </form>

</body> </html></source>


Working with the InitialValue property

   <source lang="csharp">

<%@ Page Language="VB" %> <script runat="server"> 

  Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs)
       Label1.Text = "Page is valid!"
  End Sub

</script> <html xmlns="http://www.w3.org/1999/xhtml" > <head id="Head1" runat="server"> 

   <title>RequiredFieldValidator</title>

</head> <body> 

   <form id="form1" runat="server">

       <asp:TextBox ID="TextBox1" Runat="server">My Initial Value</asp:TextBox>
       <asp:RequiredFieldValidator ID="RequiredFieldValidator1"  
                                   Runat="server" 
                                   ErrorMessage="Please change the value of the textbox!" 
                                   ControlToValidate="TextBox1" 
                                   InitialValue="My Initial Value">
       </asp:RequiredFieldValidator>
       

       <asp:Button ID="Button1" Runat="server" Text="Submit" 
        OnClick="Button1_Click" />
       

       

       <asp:Label ID="Label1" Runat="server"></asp:Label>    

   </form>

</body> </html></source>

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