Hide specified cell borders in datagridview?

Question

I want to hide one or two grid cells from my datagriview. But with this code all the grids are hidden and this is not what I want.

I want to hide one or two rectangl

Answer 1

The recommended way to hide or modify cell border style is to code the CellPainting event.

Don't worry, no actual painting is required. All you need to do is set a few fields in the e.AdvancedBorderStyle parameter.

Here is an example:

Note the 'vertically merged' look of of the cells in the 3rd column; same for the 'horizontally merged' cells at the bottom. Also the double border of a cell in the 5th column.

private void dataGridView1_CellPainting(object sender,
                                        DataGridViewCellPaintingEventArgs e)
{
    if (e.ColumnIndex == 2 && e.RowIndex == 6)
        e.AdvancedBorderStyle.Right = DataGridViewAdvancedCellBorderStyle.None;

    if (e.ColumnIndex == 2 && e.RowIndex == 1)
        e.AdvancedBorderStyle.Bottom = DataGridViewAdvancedCellBorderStyle.None;

    if (e.ColumnIndex == 4 && e.RowIndex == 4)
    {
        e.AdvancedBorderStyle.All = DataGridViewAdvancedCellBorderStyle.InsetDouble;
        e.AdvancedBorderStyle.Bottom = DataGridViewAdvancedCellBorderStyle.Single;
    }
}

Note that hiding borders is rather straight forward : Simply hide the right or the bottom border; other borderstyles require some trial and error (or a deeper understanding ;-)

Here I first set the style for all sides but as it paints the botton white (at least that's what I think it does) I then set the botton border back to single.

You may want to streamline the way the checks are done; this is just a simple example.

Update:

Here is a code to make the merging more dynamic: Use the mergeCells function to mark a cell for merging or un-merging with its right or bottom neighbour:

private void mergeCells(DataGridViewCell cell, bool mergeH, bool mergeV)
{
    string m = "";
    if (mergeH) m += "R";  // merge horizontally by hiding the right border line
    if (mergeV) m += "B"; // merge vertically by hiding the bottom border line
    cell.Tag =  m == "" ? null : m;
}

The CellPainting now looks like this:

private void customDGV1_CellPainting(object sender, DataGridViewCellPaintingEventArgs e)
{
    if (e.ColumnIndex < 0 || e.RowIndex < 0) return;
    DataGridViewCell cell = ((DataGridView)sender)[e.ColumnIndex, e.RowIndex];
    if (cell.Tag == null) return;
    string hide = cell.Tag.ToString();

    if (hide.Contains("R")) 
        e.AdvancedBorderStyle.Right = DataGridViewAdvancedCellBorderStyle.None;
    else
        e.AdvancedBorderStyle.Right = DataGridViewAdvancedCellBorderStyle.Single;

    if (hide.Contains("B")) 
        e.AdvancedBorderStyle.Bottom = DataGridViewAdvancedCellBorderStyle.None;
    else 
        e.AdvancedBorderStyle.Bottom = DataGridViewAdvancedCellBorderStyle.Single;

}

Update 2:

If you want to apply this to the ColumnHeaders you need to turn off dgv.EnableHeadersViualStyles first..