How do i set the checkbox (template) of a gridview programmatically in the code view  

 this is the code pasted in the code behind:

but it doesnt work .... 

please help ... 

 int i = 0;
                foreach (GridViewRow row in Grid_Reserve.Rows)
                {
                    i = i + 1;
                    CheckBox checkbox = row.FindControl("CheckBox1") as CheckBox;
                    string str = " select  count(*) from Issue_Book_Reserve, Books  where  Issue_Book_Reserve.Book_Id = Books.Book_Id and Books.Book_Name =  '" + Grid_Issue.Rows[i].Cells[2].Text + "' and Issue_Book_Reserve.Issue_Book_Reserve_State = 3";
                    SqlCommand checking = new SqlCommand(str, con);
                    int count = (int)checking.ExecuteScalar();
                    if (count < 1)

                        Grid_Issue.Rows[i].Cells[0].Text = "true";
                    //                    checkbox.Checked = true; //in case i use this , a null pointer exception is used



                }
            }

One thing I see right off the bat is the use of your counters. Get rid of it! During your first iteration, you'd be pointing to the row with an index of 1 which is actually the second row. You're already iterating through the rows, so simply use the "row" reference from your foreach statement for retrieving your references. Don't try to directly reference your row through the use of an index.

 ya i too found that to be true earlier ..but then that done how do i set the checkbox to be true?

any clues.. 

I'm not exactly sure what you're doing with the Sql query, but all you need to do is retrieve a reference to your CheckBox using row.FindControl and then set the Checked property from that reference.

dont u mean like this? 

CheckBox  checkbox  = Gridviewrow.findcontrol("checkbox1")

checkbox.checked = true ? 

in case its this i tried this , it doesnt work ..im missing something

Yes, except you need to cast the result of the FindControl method to a CheckBox.

CheckBox checkbox = GridVwiewrow.FindControl("checkbox1") as CheckBox

checkbox.Checked = true