ERROR: it is not a member of 'ASP.default_aspx.'

I have a problem in my code.
I always have an error.

Here is my code

<pre lang="xml"><asp:GridView ID="GridView1" runat="server"
              AutoGenerateColumns="False"
              DataKeyNames="ID"
              DataSourceID="SqlDataSource1"
              OnRowDeleted="GridView1_RowDeleted"
              OnRowUpdated="GridView1_RowUpdated"
              ShowFooter="true"
              OnRowCommand="GridView1_RowCommand">
<Columns>
    <asp:CommandField ShowDeleteButton="True"
                      ShowEditButton="True" />
    <asp:TemplateField HeaderText="ID" SortExpression="ID">
    <ItemTemplate>
    <asp:Label ID="lblID" runat="server"
                          Text='<%#Eval("ID") %>'>
    </asp:Label>
    </ItemTemplate>
    <FooterTemplate>
    <asp:Button ID="btnInsert" runat="server"
                Text="Insert" CommandName="Add" />
    </FooterTemplate>
    </asp:TemplateField>

    <asp:TemplateField HeaderText="FirstName"
                       SortExpression="FirstName">
    <ItemTemplate>
    <asp:Label ID="lblFirstName" runat="server"
               Text='<%#Eval("FirstName") %>'>
    </asp:Label>
    </ItemTemplate>
    <EditItemTemplate>
    <asp:TextBox ID="txtFirstName" runat="server"
                 Text='<%#Bind("FirstName") %>'>
    </asp:TextBox>
    </EditItemTemplate>
    <FooterTemplate>
    <asp:TextBox ID="txtFname" runat="server">
    </asp:TextBox>
    </FooterTemplate>
    </asp:TemplateField>

    <asp:TemplateField HeaderText="LastName"
                       SortExpression="LastName">
    <ItemTemplate>
    <asp:Label ID="lblLastName" runat="server"
               Text='<%#Eval("LastName") %>'>
    </asp:Label>
    </ItemTemplate>
    <EditItemTemplate>
    <asp:TextBox ID="txtLastName" runat="server"
                 Text='<%#Bind("LastName") %>'>
    </asp:TextBox>
    </EditItemTemplate>
    <FooterTemplate>
    <asp:TextBox ID="txtLname" runat="server">
    </asp:TextBox>
    </FooterTemplate>
    </asp:TemplateField>

    <asp:TemplateField HeaderText="Department"
                       SortExpression="Department">
    <ItemTemplate>
    <asp:Label ID="lblDepartment" runat="server"
               Text='<%#Eval("Department") %>'>
    </asp:Label>
    </ItemTemplate>
    <EditItemTemplate>
    <asp:TextBox ID="txtDepartmentName" runat="server"
                 Text='<%#Bind("Department") %>'>
    </asp:TextBox>
    </EditItemTemplate>
    <FooterTemplate>
    <asp:TextBox ID="txtDept" runat="server">
    </asp:TextBox>
    </FooterTemplate>
    </asp:TemplateField>

    <asp:TemplateField HeaderText="Location"
                       SortExpression="Location">
    <ItemTemplate>
    <asp:Label ID="lblLocation" runat="server"
               Text='<%#Eval("Location") %>'>
    </asp:Label>
    </ItemTemplate>
    <EditItemTemplate>
    <asp:TextBox ID="txtLocation" runat="server"
                 Text='<%#Bind("Location") %>'>
    </asp:TextBox>
    </EditItemTemplate>
    <FooterTemplate>
    <asp:TextBox ID="txtLoc" runat="server">
    </asp:TextBox>
    </FooterTemplate>
    </asp:TemplateField>
</Columns>
</asp:GridView>

<asp:SqlDataSource ID="SqlDataSource1" runat="server"
ConnectionString="<%$ ConnectionStrings:DBConString%>"
DeleteCommand="DELETE FROM [Employees] WHERE [ID] = @ID"
InsertCommand="INSERT INTO [Employees] ([FirstName],
[LastName],[Department], [Location])
VALUES (@FirstName, @LastName, @Department, @Location)"
SelectCommand="SELECT [ID], [FirstName], [LastName],
[Department], [Location] FROM [Employees]"
UpdateCommand="UPDATE [Employees] SET
[FirstName] = @FirstName, [LastName] = @LastName,
[Department] = @Department, [Location] = @Location
WHERE [ID] = @ID" OnInserted="SqlDataSource1_Inserted">

<DeleteParameters>
    <asp:Parameter Name="ID" Type="Int32" />
</DeleteParameters>
<UpdateParameters>
    <asp:Parameter Name="FirstName" Type="String" />
    <asp:Parameter Name="LastName" Type="String" />
    <asp:Parameter Name="Department" Type="String" />
    <asp:Parameter Name="Location" Type="String" />
    <asp:Parameter Name="ID" Type="Int32" />
</UpdateParameters>
<InsertParameters>
    <asp:Parameter Name="FirstName" Type="String" />
    <asp:Parameter Name="LastName" Type="String" />
    <asp:Parameter Name="Department" Type="String" />
    <asp:Parameter Name="Location" Type="String" />
</InsertParameters>
</asp:SqlDataSource>
<asp:Label ID="lblMessage" runat="server"
           Font-Bold="True"></asp:Label><br />

And the error is "it is not a member of 'ASP.default_aspx.'"
I hope you can help me.
Thanks a lot!

Tags: Visual Basic, ASP.NET