datagridview using c#
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i bind one table in my datagridview i have 4 check box in my datagridview... one for present... second one for absent... third one for morning present... fourth one for evening present... if i check only one check box i get the following error... // ERROR // Object reference not set to an instance of an object. bcz i assigned check box value to one string variable... string value11 =”aa” , value22 =”aa” , value33 =”aa” , value44 =”aa” ; con27.Open(); int rows = dataGridView1.Rows.Count; rows = rows - 1; for (int i = 0; i < rows; i++) { SqlCommand cmd27 = new SqlCommand("sp_update_att_lkg", con27); cmd27.CommandType = CommandType.StoredProcedure; value11 = dataGridView1.Rows[i].Cells[0].Value.ToString(); value22 = dataGridView1.Rows[i].Cells[1].Value.ToString(); value33 = dataGridView1.Rows[i].Cells[2].Value.ToString(); value44 = dataGridView1.Rows[i].Cells[3].Value.ToString(); string value10 = dataGridView1.Rows[i].Cells[4].Value.ToString();// S_ID string value6 = dataGridView1.Rows[i].Cells[5].Value.ToString();// name string value7 = dataGridView1.Rows[i].Cells[6].Value.ToString();// class string value8 = dataGridView1.Rows[i].Cells[7].Value.ToString();//section string value9 = dataGridView1.Rows[i].Cells[8].Value.ToString();// scode string value5 = dataGridView1.Rows[i].Cells[9].Value.ToString();// uid string dt1 = dateTimePicker1.Text; DateTime DT = DateTime.Parse(dt1); // ATTENDANCE if (value11 == "True") { value11 = "present"; } else { value11 = "absent"; } cmd27.Parameters.Add(new SqlParameter("@puid", SqlDbType.Int)); cmd27.Parameters["@puid"].Value = value5; cmd27.Parameters.Add(new SqlParameter("@pname", SqlDbType.VarChar)); cmd27.Parameters["@pname"].Value = value6; cmd27.Parameters.Add(new SqlParameter("@pclass", SqlDbType.VarChar)); cmd27.Parameters["@pclass"].Value = value7; cmd27.Parameters.Add(new SqlParameter("@psection", SqlDbType.VarChar )); cmd27.Parameters["@psection"].Value = value8; cmd27.Parameters.Add(new SqlParameter("@pcode", SqlDbType.VarChar)); cmd27.Parameters["@pcode"].Value = value9; cmd27.Parameters.Add(new SqlParameter("@pattend",SqlDbType.DateTime)); cmd27.Parameters["@pattendance"].Value = DT; cmd27.Parameters.Add(new SqlParameter("@pstatus", SqlDbType.VarChar)); cmd27.Parameters["@pstatus"].Value = value11; cmd27.Parameters.Add(new SqlParameter("@ps_id", SqlDbType.VarChar)); cmd27.Parameters["@ps_id"].Value = value10; cmd27.ExecuteNonQuery(); } expecting suggestion