ASP.Net/Validation by Control/Validate DropDownList
RequiredFieldValidator for asp dropdownlist (C#)
<%@ Page Language="C#" %>
<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" />
<br /><br />
<asp:Button
id="btnSubmit"
Text="Submit"
Runat="server" OnClick="btnSubmit_Click" />
<hr />
<asp:Label
id="lblResult"
Runat="server" />
</div>
</form>
</body>
</html>
Validate asp dropdownlist in VB.net
<%@ Page Language="VB" %>
<script runat="server">
Protected Sub btnSubmit_Click(ByVal sender As Object, ByVal e As System.EventArgs)
If Page.IsValid Then
lblResult.Text = dropFavoriteColor.SelectedValue
End If
End Sub
</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" />
<br /><br />
<asp:Button
id="btnSubmit"
Text="Submit"
Runat="server" OnClick="btnSubmit_Click" />
<hr />
<asp:Label
id="lblResult"
Runat="server" />
</div>
</form>
</body>
</html>