ASP.Net/Validation by Control/Validate DropDownList

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RequiredFieldValidator for asp dropdownlist (C#)

   <source lang="csharp">

<%@ 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">
   <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>
   
  


Validate asp dropdownlist in VB.net

   <source lang="csharp">

<%@ 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">
   <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>