how to hide templatefield in gridview

Question

I am repeating this question because i am not able to find answer from anywhere.

I Have a GridView in .aspx page. I want to hide columns based on aspx.cs BindData() method.

I have tried using below code but not able to hide. I am using Asp.net with C#.

Below is my GridView with columns and I have also included the Button click code.

If I select "T-L" which is in below else-if Ladder i am getting this error

DataBinding: 'System.Data.DataRowView' does not contain a property with the name 'tutorial'.
I have marked a test case error in .aspx

For temporary to make my program work i am using 4 gridview to bind 4 query,which is not feasible...How can i hide templatefield invisible based on conditions... plz help me..

<GridView>
    <Columns>
        <asp:BoundField DataField="id" HeaderText="Id" SortExpression="id" 
            Visible="false" />                     
        <asp:TemplateField HeaderText="RollNo" >
            <ItemTemplate>
                <%# Eval("st_rollno")%>
            </ItemTemplate>
            <EditItemTemplate>    
                <asp:TextBox ID="tbsturollno" runat="Server"
                    Text='<%# Eval("st_rollno") %>'></asp:TextBox>
            </EditItemTemplate>   
        </asp:TemplateField>

        <asp:TemplateField HeaderText="Name">
            <ItemTemplate>
                <%# Eval("st_name")%>
            </ItemTemplate>
            <EditItemTemplate>    
                <asp:TextBox ID="tbstuname" runat="Server"
                    Text='<%# Eval("st_name") %>'></asp:TextBox>
            </EditItemTemplate>               
        </asp:TemplateField>

        <asp:TemplateField HeaderText="Theory">
            <ItemTemplate>
                <%# Eval("theory")%>
            </ItemTemplate>
            <EditItemTemplate> 
                <asp:TextBox ID="tbtheory" runat="Server"
                    Text='<%# Eval("theory") %>'></asp:TextBox>
            </EditItemTemplate>   
        </asp:TemplateField>

        <asp:TemplateField HeaderText="Total" >
            <ItemTemplate>
                <%# Eval("ttotal")%>
            </ItemTemplate>
            <EditItemTemplate>   
                <asp:TextBox ID="tbtheorytotal" runat="Server"
                    Text='<%# Eval("ttotal") %>'></asp:TextBox>
            </EditItemTemplate>   
        </asp:TemplateField>

        <asp:TemplateField HeaderText="Lab" >
            <ItemTemplate>
                <%# Eval("lab")%>
            </ItemTemplate>
            <EditItemTemplate>
                <asp:TextBox ID="tblab" runat="Server"
                    Text='<%# Eval("lab") %>'>
                </asp:TextBox>
            </EditItemTemplate>   
        </asp:TemplateField>

        <asp:TemplateField HeaderText="Total" >
            <ItemTemplate>
                <%# Eval("ltotal")%>
            </ItemTemplate>
            <EditItemTemplate>
                <asp:TextBox ID="tblabtotal" runat="Server"
                    Text='<%# Eval("ltotal") %>'></asp:TextBox>
            </EditItemTemplate>   
        </asp:TemplateField>

        <asp:TemplateField HeaderText="Tutorial" >
            <ItemTemplate>
   *Error is HERE             <%# Eval("tutorial")%>
            </ItemTemplate>
            <EditItemTemplate>   
                <asp:TextBox ID="tbtutorial" runat="Server"
                    Text='<%# Eval("tutorial") %>'></asp:TextBox>
            </EditItemTemplate>   
        </asp:TemplateField>

        <asp:TemplateField HeaderText="Total" >
            <ItemTemplate>
                <%# Eval("tutotal")%>
            </ItemTemplate>
            <EditItemTemplate>    
                <asp:TextBox ID="tbtutorialtotal" runat="Server"
                    Text='<%# Eval("tutotal") %>'></asp:TextBox>
            </EditItemTemplate>   
        </asp:TemplateField>        
    </Columns>
</GridView>

private void BindData()
{
    DataTable dt = new DataTable();
    using (SqlConnection con = new SqlConnection(ConnectionString))
    {
        if (stype.Equals("L"))
        {
            query = "SELECT [id], [st_rollno], [st_name], [lab], [ltotal] FROM [Attendence_Subject_Wise] WHERE (([branch_name] = @branch_name) AND ([scode] = @scode) AND ([sem_no] = @sem_no) AND ([sess_no] = @sess_no)) ORDER BY [st_rollno]";
            GridView1.Columns[3].Visible = false;
            GridView1.Columns[4].Visible = false;
            GridView1.Columns[7].Visible = false;
            GridView1.Columns[8].Visible = false;
        }
        else if (stype.Equals("T"))
        {
            query = "SELECT [id], [st_rollno], [st_name], [theory], [ttotal] FROM [Attendence_Subject_Wise] WHERE (([branch_name] = @branch_name) AND ([scode] = @scode) AND ([sem_no] = @sem_no) AND ([sess_no] = @sess_no)) ORDER BY [st_rollno]";
            GridView1.Columns[5].Visible = false;
            GridView1.Columns[6].Visible = false;
            GridView1.Columns[7].Visible = false;
            GridView1.Columns[8].Visible = false;
        }
        else if (stype.Equals("T-L"))
        {
            GridView1.Columns[7].Visible = false;
            GridView1.Columns[8].Visible = false;    
            query = "SELECT [id], [st_rollno], [st_name], [theory], [ttotal], [lab], [ltotal] FROM [Attendence_Subject_Wise] WHERE (([branch_name] = @branch_name) AND ([scode] = @scode) AND ([sem_no] = @sem_no) AND ([sess_no] = @sess_no)) ORDER BY [st_rollno]";
        }
        else
        {    
            query = "SELECT [id], [st_rollno], [st_name],[theory], [ttotal], [lab], [ltotal], [tutorial], [tutotal] FROM [Attendence_Subject_Wise] WHERE (([branch_name] = @branch_name) AND ([scode] = @scode) AND ([sem_no] = @sem_no) AND ([sess_no] = @sess_no)) ORDER BY [st_rollno]";
        }

        com = new SqlCommand(query);
        com.Parameters.Add("@branch_name", dept);
        com.Parameters.Add("@scode", dpsubject.SelectedItem.Text.ToString());
        com.Parameters.Add("@sem_no", Int32.Parse(dpsemno.SelectedItem.Text.ToString()));
        com.Parameters.Add("@sess_no",Int32.Parse(dpsessional.SelectedItem.Text.ToString()));

        using (SqlDataAdapter sda = new SqlDataAdapter())
        {
            com.Connection = con;
            con.Open();
            sda.SelectCommand = com;
            sda.Fill(dt);
            GridView1.DataSource = dt;
            GridView1.DataBind();
            con.Close();
        }    
    }
}

protected void bsubmit_Click(object sender, EventArgs e)
{
    this.BindData();
}

Answer 1

Try having your query still return a result for each column you want to hide even though you won't use those values. In the query for when stype is "T-L", change query from this:

query = "SELECT [id], [st_rollno], [st_name], [theory], [ttotal], [lab], [ltotal] FROM [Attendence_Subject_Wise] WHERE (([branch_name] = @branch_name) AND ([scode] = @scode) AND ([sem_no] = @sem_no) AND ([sess_no] = @sess_no)) ORDER BY [st_rollno]";

To this:

query = "SELECT [id], [st_rollno], [st_name], [theory], [ttotal], [lab], [ltotal], '' as tutorial, '' as tutotal FROM [Attendence_Subject_Wise] WHERE (([branch_name] = @branch_name) AND ([scode] = @scode) AND ([sem_no] = @sem_no) AND ([sess_no] = @sess_no)) ORDER BY [st_rollno]";

EDIT:

To hide the column, add the following method to your code behind:

protected void GridView_DataBound(object sender, GridViewRowEventArgs e)
{
    if (stype.Equals("T-L"))
    {
        MyGridView.Columns[7].Visible = false;
        MyGridView.Columns[8].Visible = false;
    }
}

And subscribe to the DataBound event on the GridView. Notice that I added an ID to the GridView so I can reference it from the code behind.

<GridView ID="MyGridView" OnDataBound="GridView_DataBound">