C# DataTable Foreach Loop

Question

Anyone can please tell me what I m doing wrong here. I have a datagridview that is automatically filled at runtime using a dataset. Also In this datagridview each column have a dataGridViewCheckBoxColumn. Now what I am trying to do in the code below is to programmatically create and fill a new datatable "dt". And then loop thru this "dt" and if the row exists in "dt" then set the dataGridViewCheckBoxColumn value to true in my datagridview. Thank You

   1:  try

   2:  {

   3:  catalog_id = (string)(comboBox6.SelectedValue);

   4:  major_id = (string)(comboBox5.SelectedValue);

   5:  coursesBox.Visible = true;

   6:  categorie_id = dataGridView4.Rows[e.RowIndex].Cells[e.ColumnIndex].FormattedValue.ToString();

   7:  DataTable dt = new DataTable();

   8:  // Fill the Set with the data

   9:  using (SqlConnection conn = new SqlConnection(connString))

  10:  {

  11:  StringBuilder query = new StringBuilder();

  12:  query.Append("SELECT a.course_id AS Courses, b.course_title AS Title, b.course_credit AS Credit, c.categories_desc AS Categories FROM degree_requirements a, Courses b, categories c, degree d WHERE a.course_id = b.course_id AND a.categories_id = c.categories_id AND a.degree_id = d.degree_id AND a.catalog_id = @ctl AND a.degree_id = @maj AND c.categories_desc = @cat");

  13:  SqlCommand cmd = new SqlCommand();

  14:  cmd.Connection = conn;

  15:  cmd.CommandText = query.ToString();

  16:  cmd.CommandType = CommandType.Text;

  17:  cmd.Parameters.AddWithValue("ctl", catalog_id);

  18:  cmd.Parameters.AddWithValue("maj", major_id);

  19:  cmd.Parameters.AddWithValue("cat", categorie_id);

  20:  //Passing the query and connection String

  21:  using (SqlDataAdapter da = new SqlDataAdapter(cmd))

  22:  {

  23:  da.Fill(dt);

  24:  }

  25:  }

  26:  // TO DO: Itierate thru the dataTable and If the row exist select the check box

  27:  //Loop over the Rows

  28:  foreach (DataGridViewRow dataGridRow in dataGridView1.Rows)

  29:  {

  30:  foreach(DataRow dr in dt.Rows)

  31:  {

  32:  //Loop over the items

  33:  foreach (var item in dr.ItemArray)

  34:  {

  35:  dataGridRow.Cells["dataGridViewCheckBoxColumn1"].Value = true;

  36:  }

  37:  }

  38:  }

  39:  groupBox3.Visible = true;

  40:  }

  41:  catch (System.Exception ex)

  42:  {

  43:  System.Windows.Forms.MessageBox.Show(ex.Message);

  44:  }