Object reference not set to an instance of an object

Hi, am having trouble performing CRUD operation from my gridview.am getting the error"Object reference not set to an instance of an object"..the error is at this line of code

" (e.Row.Cells[2].Controls[2] as LinkButton).Attributes["onclick"] = "return confirm('Do you want to delete this row?');";

below i have the codes am using..this is the aspx code for populating the gridview

OnRowDataBound="OnRowDataBound" OnRowEditing="OnRowEditing" OnRowCancelingEdit="OnRowCancelingEdit"
OnRowUpdating="OnRowUpdating" OnRowDeleting="OnRowDeleting" EmptyDataText="No records has been added.">

















































ItemStyle-Width="150" />

CompanyID

BranchID

DepartmentID

GLaccountNumber

CostCenterID

CostPercentage

private void BindGrid()
{
string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
using (SqlConnection con = new SqlConnection(constr))
{
using (SqlCommand cmd = new SqlCommand("Customers_CRUD"))
{
cmd.Parameters.AddWithValue("@Action", "SELECT");
using (SqlDataAdapter sda = new SqlDataAdapter())
{
cmd.CommandType = CommandType.StoredProcedure;
cmd.Connection = con;
sda.SelectCommand = cmd;
using (DataTable dt = new DataTable())
{
sda.Fill(dt);
GridView1.DataSource = dt;
GridView1.DataBind();
}
}
}
}
}

protected void Insert(object sender, EventArgs e)
{
string CompanyID = txtCompanyID.Text;
string BranchID = txtBranchID.Text;
string DepartmentID = txtDepartmentID.Text;
string GLaccountNumber = txtGLaccountNumber.Text;
string CostCenterID = txtCostCenterID.Text;
string CostPercentage = txtCostPercentage.Text;
string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
using (SqlConnection con = new SqlConnection(constr))
{
using (SqlCommand cmd = new SqlCommand("Customers_CRUD"))
{
cmd.CommandType = CommandType.StoredProcedure;
cmd.Parameters.AddWithValue("@Action", "INSERT");
cmd.Parameters.AddWithValue("@CompanyID", CompanyID);
cmd.Parameters.AddWithValue("@BranchID", BranchID);
cmd.Parameters.AddWithValue("@DepartmentID", DepartmentID);
cmd.Parameters.AddWithValue("@GLaccountNumber", GLaccountNumber);
cmd.Parameters.AddWithValue("@CostCenterID", CostCenterID);
cmd.Parameters.AddWithValue("@CostPercentage", CostPercentage);
cmd.Connection = con;
con.Open();
cmd.ExecuteNonQuery();
con.Close();
}
}
this.BindGrid();
}

protected void OnRowEditing(object sender, GridViewEditEventArgs e)
{
GridView1.EditIndex = e.NewEditIndex;
this.BindGrid();
}

protected void OnRowCancelingEdit(object sender, EventArgs e)
{
GridView1.EditIndex = -1;
this.BindGrid();
}

protected void OnRowUpdating(object sender, GridViewUpdateEventArgs e)
{
GridViewRow row = GridView1.Rows[e.RowIndex];
int TransactionId = Convert.ToInt32(GridView1.DataKeys[e.RowIndex].Values[0]);
string CompanyID = (row.FindControl("txtCompanyID") as TextBox).Text;
string BranchID = (row.FindControl("txtBranchID") as TextBox).Text;
string DepartmentID = (row.FindControl("txtDepartmentID ") as TextBox).Text;
string GLaccountNumber = (row.FindControl("txtGLaccountNumber") as TextBox).Text;
string CostCenterID = (row.FindControl("txtCostCenterID") as TextBox).Text;
string CostPercentage = (row.FindControl("txtCostPercentage") as TextBox).Text;

string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
using (SqlConnection con = new SqlConnection(constr))
{
using (SqlCommand cmd = new SqlCommand("Customers_CRUD"))
{
cmd.CommandType = CommandType.StoredProcedure;
cmd.Parameters.AddWithValue("@Action", "UPDATE");
cmd.Parameters.AddWithValue("@CompanyID", CompanyID);
cmd.Parameters.AddWithValue("@BranchID", BranchID);
cmd.Parameters.AddWithValue("@DepartmentID", DepartmentID);
cmd.Parameters.AddWithValue("@GLaccountNumber", GLaccountNumber);
cmd.Parameters.AddWithValue("@CostCenterID", CostCenterID);
cmd.Parameters.AddWithValue("@CostPercentage", CostPercentage);
cmd.Connection = con;
con.Open();
cmd.ExecuteNonQuery();
con.Close();
}
}
GridView1.EditIndex = -1;
this.BindGrid();
}

protected void OnRowDataBound(object sender, GridViewRowEventArgs e)
{
if (e.Row.RowType == DataControlRowType.DataRow && e.Row.RowIndex != GridView1.EditIndex)
{
(e.Row.Cells[2].Controls[2] as LinkButton).Attributes["onclick"] = "return confirm('Do you want to delete this row?');";
}
}

protected void OnRowDeleting(object sender, GridViewDeleteEventArgs e)
{
int TransactionId = Convert.ToInt32(GridView1.DataKeys[e.RowIndex].Values[0]);
string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
using (SqlConnection con = new SqlConnection(constr))
{
using (SqlCommand cmd = new SqlCommand("Customers_CRUD"))
{
cmd.CommandType = CommandType.StoredProcedure;
cmd.Parameters.AddWithValue("@Action", "DELETE");
cmd.Parameters.AddWithValue("@TransactionId", TransactionId);
cmd.Connection = con;
con.Open();
cmd.ExecuteNonQuery();
con.Close();
}
}
this.BindGrid();
}