How To Update A Column In A DataGrid Using C#.NET? I am getting InvalidCastException as (Specified cast is not valid) while updating 2nd column in a datagrid? Id,firstname,lastname are the three columns of my datagrid respectively. I wanted to edit the second column(lastname) and update it. I did the following code in DataGrid's updatecommand(),but failed to update ! Int varid=(int)DataGrid1.DataKeys[e.Item.ItemIndex]; TextBox lnm=(TextBox)e.Item.Cells[2].Controls[0]; string str=lnm.Text ; SqlCommand cmd=new SqlCommand("update customer set lastname='" + str + "' where id=" + varid + "",con); cmd.ExecuteNonQuery(); DataGrid1.EditItemIndex=- 1; DataGrid1.DataBind();

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