Hi sat
refer below code,
HTML
<div>
<asp:DropDownList ID="DropDownList1" runat="server">
<asp:ListItem Text="Item1" Value="Item1"></asp:ListItem>
<asp:ListItem Text="Item2" Value="Item2"></asp:ListItem>
<asp:ListItem Text="Item3" Value="Item3"></asp:ListItem>
<asp:ListItem Text="Item4" Value="Item4"></asp:ListItem>
<asp:ListItem Text="Item5" Value="Item5"></asp:ListItem>
<asp:ListItem Text="Item6" Value="Item6"></asp:ListItem>
<asp:ListItem Text="Item7" Value="Item7"></asp:ListItem>
<asp:ListItem Text="Item8" Value="Item8"></asp:ListItem>
<asp:ListItem Text="Item9" Value="Item9"></asp:ListItem>
</asp:DropDownList>
<asp:DropDownList ID="DropDownList2" runat="server">
<asp:ListItem Text="Item1" Value="Item1"></asp:ListItem>
<asp:ListItem Text="Item3" Value="Item3"></asp:ListItem>
<asp:ListItem Text="Item5" Value="Item5"></asp:ListItem>
<asp:ListItem Text="Item8" Value="Item8"></asp:ListItem>
<asp:ListItem Text="Item9" Value="Item9"></asp:ListItem>
</asp:DropDownList>
<asp:Button Text="Get UnCommon" runat="server" OnClick="OnGet" />
<hr />
<asp:GridView runat="server" ID="GridView1"></asp:GridView>
</div>
Code
C#
protected void OnGet(object sender, EventArgs e)
{
List<string> items1 = new List<string>();
List<string> items2 = new List<string>();
foreach (ListItem item in DropDownList1.Items)
{
items1.Add(item.Value);
}
foreach (ListItem item in DropDownList2.Items)
{
items2.Add(item.Value);
}
List<string> unCommonItems = items1.Except(items2).ToList();
GridView1.DataSource = unCommonItems;
GridView1.DataBind();
}
VB.Net
Protected Sub OnGet(ByVal sender As Object, ByVal e As EventArgs)
Dim items1 As List(Of String) = New List(Of String)()
Dim items2 As List(Of String) = New List(Of String)()
For Each item As ListItem In DropDownList1.Items
items1.Add(item.Value)
Next
For Each item As ListItem In DropDownList2.Items
items2.Add(item.Value)
Next
Dim unCommonItems As List(Of String) = items1.Except(items2).ToList()
GridView1.DataSource = unCommonItems
GridView1.DataBind()
End Sub
Screenshot