Hello forum,

I am having issue with my delete code. I have a gridview where records are displayed. The data that are bind in the gridview are from different tables; when user selects a value from the drop-down List, data will be displayed in the gridview based on the selected value in the drop-down List.

In the gridview, delete button is shown based on the drop-down List too. For example if a user selects certificate in the dropdown, then the delete button will be hidden, but when cards is selected, then the delete button shows.

When I click on the delete button is gives me this error as shown below

Here is my HTML and code to delete

                <asp:DropDownList runat="server" ID="ddlTables" Width="100%" Height="20px" AutoPostBack="true">
                    <asp:ListItem Text="Select Document Type" />
                    <asp:ListItem Text="Users" Value="Team" />
                    <asp:ListItem Text="ID Cards" Value="Cards" />
                    <asp:ListItem Text="Certificates" Value="Certificates" />
                    <asp:ListItem Text="Reciepts" Value="reciepts" />
                    <asp:ListItem Text="Tickets" Value="Tickets" />
                </asp:DropDownList>
                <asp:Label ID="Label1" runat="server" Font-Bold="true" Text="Start Date"></asp:Label>
                <asp:TextBox ID="TextBox1" runat="server" Width="100%" Height="20px" type="date"></asp:TextBox>
                <asp:Label ID="Label2" runat="server" Font-Bold="true" Text="End Date"></asp:Label>
                <asp:TextBox ID="Dat" runat="server" Width="100%" Height="20px" type="date"></asp:TextBox>
                <br />
                <br />
                <asp:Button ID="Button2" runat="server" Text="Search Records/Activities" Font-Size="Small" Width="100%" BackColor="SteelBlue" Class="btn btn-primary" OnClick="Button2_Click"/>
                <br />
                <br />
                <div class="parent">
                    <div class="child" id="midcont" style="width: 100%; font-family: Constantia;">
                        <div class="Gridv" style="height: 380px; overflow: scroll">
                            <asp:GridView ID="GridView1" runat="server" OnRowDataBound="OnRowDataBound" GridLines="None" HeaderStyle-BackColor="#D3D9E5" OnRowDeleting="OnRowDeleting"
                              HeaderStyle-ForeColor="#00003D" Width="100%" Height="80px" HeaderStyle-Height="30px" AllowPaging="true" PageSize="6">
                                <EmptyDataTemplate>
                                    <div style="text-align: center; font-weight: bolder; font-size: medium;">
                                        <asp:Label ID="labelTemp" runat="server" Text="No Record/Activity"></asp:Label>
                                    </div>
                                </EmptyDataTemplate>
                                <Columns>
                                    <asp:TemplateField HeaderText="Image">
                                        <ItemTemplate>
                                            <asp:Image ID="Image1" runat="server" Width="40px" Height="40px" />
                                        </ItemTemplate>
                                    </asp:TemplateField>
                                    <asp:CommandField ButtonType="Button" ShowDeleteButton="true" ItemStyle-ForeColor="#00003D" ItemStyle-Width="150" ControlStyle-Font-Size="Small"
                                        ControlStyle-BackColor="SteelBlue" ControlStyle-BorderStyle="None" ControlStyle-ForeColor="White" ControlStyle-Width="40" HeaderText="Action" />
                                </Columns>
                            </asp:GridView>
                        </div>
                    </div>
                </div>

CODE

    protected void OnRowDeleting(object sender, GridViewDeleteEventArgs e)
    {
        int Uid = Convert.ToInt32(GridView1.DataKeys[e.RowIndex].Values[0]);
        string query = "";
        if (ddlTables.SelectedValue.ToLower() == "team")
        {
            query = "DELETE FROM Users WHERE Uid = Uid";
        }
        if (ddlTables.SelectedValue.ToLower() == "cards")
        {
            query = "DELETE FROM CardTbl WHERE Uid = @Uid";
        }

        if (ddlTables.SelectedValue.ToLower() == "certificates")
        {
            query = "DELETE FROM CertTbl WHERE Uid = @Uid";
        }

        using (SqlConnection con = new SqlConnection("Data Source = (LocalDB)\\MSSQLLocalDB; AttachDbFilename =| DataDirectory |\\Dataregister.mdf; Integrated Security = True"))
        {
            using (SqlCommand cmd = new SqlCommand(query))
            {
                cmd.Parameters.AddWithValue("@Uid", Uid);
                cmd.Connection = con;
                con.Open();
                cmd.ExecuteNonQuery();
                con.Close();
            }
        }
    }