DataTable oldTable = new DataTable();
...
DataTable newTable = new DataTable();
newTable.Columns.Add("Field Name");
for (int i = 0; i < oldTable.Rows.Count; i++)
newTable.Columns.Add();
for (int i = 0; i < oldTable.Columns.Count; i++)
{
DataRow newRow = newTable.NewRow();
newRow[0] = oldTable.Columns[i].Caption;
for (int j = 0; j < oldTable.Rows.Count; j++)
newRow[j+1] = oldTable.Rows[j][i];
newTable.Rows.Add(newRow);
}
dataGridView.DataSource = newTable;