Question

How to freeze first row in Datagridview when using a custom SortComparer?
Without SortComparer row[x].froozen = true; would do it.
But with a SortComparer it doesnt work

Here is my SortComparer Code:

DataGridView dg = (DataGridView)sender;

        if (e.Column.Index == 0)
        {
            e.SortResult = System.String.Compare(e.CellValue1.ToString(), e.CellValue2.ToString());

            if (e.SortResult == 0)
            {
                e.SortResult = System.String.Compare(
                    dg.Rows[e.RowIndex1].Cells[1].Value.ToString(),
                    dg.Rows[e.RowIndex2].Cells[1].Value.ToString());
            }

            e.Handled = true;
        }
        else if (e.Column.Index == 1)
        {

            e.SortResult = System.String.Compare(e.CellValue1.ToString(), e.CellValue2.ToString());

            if (e.SortResult == 0)
            {
                e.SortResult = System.String.Compare(
                    dg.Rows[e.RowIndex1].Cells[0].Value.ToString(),
                    dg.Rows[e.RowIndex2].Cells[0].Value.ToString());
            }
            e.Handled = true;
        }

Answer 1

You could extend your SortComparer to check if the first row index is the top row or not. If it is, set the e.SortResult = 0 or else run whatever code you want to sort with.

  private void dataGridView1_SortCompare(object sender,  DataGridViewSortCompareEventArgs e)
  {
       DataGridView dg = (DataGridView)sender;
       if (e.RowIndex1 == 0) {
           e.SortResult = 0;
           e.Handled = true;
       } else {
         // rest of your comparison code
       }
  }

or you can make it more fancy by checking if the row is frozen or not:

EDIT the following does not work since the Frozen property of a Row gets set to false by default for some reason

  private void dataGridView1_SortCompare(object sender,  DataGridViewSortCompareEventArgs e)
  {
       DataGridView dg = (DataGridView)sender;
       if (dg.Rows[e.RowIndex1].Frozen) {
           e.SortResult = -1;
           e.Handled = true;
       } else {
         // rest of your comparison code
       }
  }

EDIT The e.SortResult = 0 instead of -1 as rows that are equal will be sorted based on their current position.