After having done some research, I believe I am asking the same question as Remove richtextbox SelectionBackColor. I have encountered the same issue, but I believe the answers in that thread were insufficient as the question was not clearly explained. Please see below:
In a RichTextBox, how do I remove a custom BackColor from some, but not all, of the text (SelectionBackColor) so that it assumes the BackColor of the control even if that BackColor changes in the future?
I have a method that highlights some text and changes its BackColor using SelectionBackColor. I have another method that changes the BackColor of the entire control. These events can happen independently.
If I want to "remove" some SelectionBackColor, I can try to set the SelectionBackColor to Color.Transparent, but it ends up being White. That is fine, temporarily, if my RichTextBox's current BackColor is White. If I set SelectionBackColor to the current BackColor, it is fine temporarily, until that BackColor changes from another method.
After the RichTextBox.BackColor has changed, any places that were previously highlighted use White or the previous BackColor, instead of assuming the new color like text that had not previously highlighted.
I have tried deleting and replacing the text, but that negates the ability to retain any other custom formatting of that text, to my knowledge. Setting SelectionBackColor to null does not work.
One can easily see what I am talking about using the code below:
protected override void OnLostFocus(EventArgs e)
{
base.OnLostFocus(e);
this.BackColor = Color.Gray;
if (SelectionLength > 0)
{
SelectionBackColor = Color.Yellow;
}
}
protected override void OnGotFocus(EventArgs e)
{
base.OnGotFocus(e);
this.ResetBackColor();
if (SelectionLength > 0)
{
// The goal of this line is to "remove" the yellow.
// By assigning it any value, it seems to have lost
// the ability to use the control's BackColor normally.
SelectionBackColor = this.BackColor;// or Color.Transparent
}
}
Type some text into a custom RichTextBox object with the code above, highlight a small portion of it, then make the box lose focus. You will see the highlighted text in yellow. Then, make the box gain focus. The yellow background will go away, as expected. However, if you move your caret elsewhere in the text and make the control lose focus again, you will see the previously-highlighted text does not assume the gray background color.
