Use the RequiredFieldValidator's InitialValue to set a default value : RequiredFieldValidator « Validation « ASP.NET Tutorial






<%@ 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">
    <div>

    <asp:Label
        id="lblFavoriteColor"
        Text="Favorite Color:"
        AssociatedControlID="dropFavoriteColor"
        Runat="server" />
    <br />
    <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" />
    </div>
    </form>
</body>
</html>








8.11.RequiredFieldValidator
8.11.1.RequiredFieldValidator requires a user to enter a value into a form field before submitting the form.
8.11.2.Use asp:RequiredFieldValidator to check the input of an asp:TextBox (VB.net)
8.11.3.Use the RequiredFieldValidator's InitialValue to set a default value
8.11.4.Specify ErrorMessage for asp:RequiredFieldValidator
8.11.5.asp:RequiredFieldValidator will be converted to JavaScript Code after loading in client side
8.11.6.A simple use of the RequiredFieldValidator server control (C#)
8.11.7.Text field of RequiredFieldValidator server control (VB)
8.11.8.Placing values between nodes
8.11.9.Working with the InitialValue property
8.11.10.Using two RequiredFieldValidator controls for one form element
8.11.11.Validating Drop-Down Lists with the RequiredFieldValidator Control
8.11.12.Using images for error notifications
8.11.13.Disabling client-side validations in a validation control
8.11.14.Using sound for error notifications
8.11.15.EnableClientScript=false, Display=Static
8.11.16.RequiredFieldValidator for login page
8.11.17.RequiredFieldValidator with server side validation
8.11.18.Hard code error message
8.11.19.RequiredFieldValidator Dynamic Display