For Grid view How to write update for using check box

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C#

i am doing the application in grid view using check box.

Database field for checkbox is as follows;
Activate datatype bit is used

source code as follows;

<asp:TemplateField HeaderText ="select" HeaderStyle-HorizontalAlign ="left">
     <itemtemplate>
     <asp:CheckBox ID="chkdelete" runat = "server" ForeColor="black" />
     </itemtemplate>

in aspx.cs page code as follows;
for the update the checkbox value to the database.

 protected void ResultGridView_RowUpdating(object sender, GridViewUpdateEventArgs e)
    {
        TextBox txtFName = (TextBox)ResultGridView.Rows[e.RowIndex].FindControl("txtFName");
        TextBox txtLName = (TextBox)ResultGridView.Rows[e.RowIndex].FindControl("txtLName");
        TextBox txtCity = (TextBox)ResultGridView.Rows[e.RowIndex].FindControl("txtCity");
        TextBox txtState = (TextBox)ResultGridView.Rows[e.RowIndex].FindControl("txtState");
        TextBox txtCountry = (TextBox)ResultGridView.Rows[e.RowIndex].FindControl("txtCountry");
        TextBox txtDescription = (TextBox)ResultGridView.Rows[e.RowIndex].FindControl("txtDescription");

        SqlConnection conn = new SqlConnection("Server=(local);initial catalog=master;Trusted_Connection=True");
        cmd.Connection = conn;
        cmd.CommandText = "UPDATE Vendors SET VendorFName ='" + txtFName.Text + "',VendorLName ='" + txtLName.Text + "',VendorCity ='" + txtCity.Text + "',VendorState ='" + txtState.Text + "',VendorCountry ='" + txtCountry.Text + "',VendorDescription ='" + txtDescription.Text + "'  WHERE VendorId='" + ResultGridView.DataKeys[e.RowIndex].Values[0].ToString() + "'";
        conn.Open();
        cmd.ExecuteNonQuery();
        ResultGridView.EditIndex = -1;
        FillVendorGrid();
        conn.Close();
    }

cmd.CommandText = "UPDATE Vendors SET VendorFName ='" + txtFName.Text + "',VendorLName ='" + txtLName.Text + "',VendorCity ='" + txtCity.Text + "',VendorState ='" + txtState.Text + "',VendorCountry ='" + txtCountry.Text + "',VendorDescription ='" + txtDescription.Text + "'  WHERE VendorId='" + ResultGridView.DataKeys[e.RowIndex].Values[0].ToString() + "'";

from the above code for updating check box how to write the code.please help me for how to write the code for check box.

how to write the code in asp.net using csharp.