Object reference not set to an instance of an object

Question

private void GetColumns(string key, DataGridView dataGrid)

{

string strQuery = string.Format("select col_index, col_name, display_name, col_type, visible, col_width from rayonpos.datagridcolumns where source_key = '{0}' order by col_index", key);

DataTable dtColumns = DataService.ExecuteQueryAndReturnTable(strQuery);

if (dtColumns.Rows.Count > 0)

{

dataGrid.Columns.Clear();

foreach (DataRow dtRow in dtColumns.Rows)

{

DataGridViewColumn dgvCol = null;

if (dtRow["col_type"].ToString().ToUpper() == "TEXT")

{

dgvCol = new DataGridViewTextBoxColumn();

}

dgvCol.Name = dtRow["col_name"].ToString();

dgvCol.HeaderText = dtRow["display_name"].ToString();

dgvCol.Visible = Convert.ToBoolean(dtRow["visible"]);

dgvCol.Width = Convert.ToInt16(dtRow["col_width"]);

dataGrid.Columns.Insert(Convert.ToInt16(dtRow["col_index"]), dgvCol);

}

}

}