TableLayoutPanel第一列没有边框？

Question

I have a class that extends TableLayoutPanel defined/constructed as follows:

public class MyTableLayout : TableLayoutPanel
{
    public MyTableLayout()
    {
        this.ColumnCount = 5;
        this.RowCount = 1;
        this.CellBorderStyle = TableLayoutPanelCellBorderStyle.Outset;
    }
}

When my table is drawn it has borders around all 5 columns (as one would expect given the code to set the CellBorderStyle above).

Is there a way I can prevent a border from being drawn around the first column?

I know you can add a CellPaint callback:

this.CellPaint += tableLayoutPanel_CellPaint;

and in this callback you can do things such as change the border color for a particular column:

private void tableLayoutPanel_CellPaint(object sender, TableLayoutCellPaintEventArgs e)
{
    if (e.Column == 0 && e.Row == 0)
    {
        e.Graphics.DrawRectangle(new Pen(Color.Red), e.CellBounds);
    }
}

But how do you draw "No" rectangle at all?

I tried setting the color to Color.Empty but that didn't work:

e.Graphics.DrawRectangle(new Pen(Color.Empty), e.CellBounds);

Answer 1

Try it the other way around. Only draw the borders around the cells you want to have a border:

private void tableLayoutPanel_CellPaint(object sender, 
                                        TableLayoutCellPaintEventArgs e) {
  if (e.Column > 0 && e.Row == 0) {
    e.Graphics.DrawRectangle(new Pen(Color.Red), e.CellBounds);
  }
}

Obviously, set your borders back to none so the painting can take over the job:

this.CellBorderStyle = TableLayoutPanelCellBorderStyle.None;

Answer 2

The painting of the cell's borders is performed by TableLayoutPanel in the OnPaintBackground override.

To modify the way your borders are painted, you need to set no borders (so the base class doesn't paint anything), and then paint all of the other borders in your own override of OnPaintBackground.

TableLayoutPanel uses an internal function, ControlPaint.PaintTableCellBorder to perform the border painting. Since you can't use it, you should have a look at the source code (with Reflector or ILSpy) to see how they did it.