Context.Items.Contains
<%@ Page Language="vb" %> <html> <head> <script runat="server"> Sub Page_Load() Context.Items("Foo")="Bar" Context.Items.Add("Bar","Foo") Message.Text = "Context.Items.Contains(""Foo"") is " & _ Context.Items.Contains("Foo") End Sub </script> </head> <body> <asp:label id="Message" runat="server"/> </body> </html>