Rich Text Box how to highlight text block

Question

I need a certain portion of my text in RTB to be highlighted not in the sense of changing the font style/color, but in the sense of making a block selection with a particula

Answer 1

Yes you can set the BackColor of a RichTextBox Selection using the RichTextBox.SelectionBackColor Property.

int blockStart = 1; //arbitrary numbers to test
int blockLength = 15;
richTextBox1.SelectionStart = blockStart;
richTextBox1.SelectionLength = blockLength;
richTextBox1.SelectionBackColor = Color.Yellow;

Answer 2

Here I have created CustomRichTextBox to achieve this.

The source code a long with scenario is explained here. If you interested then you can reuse this usercontrol directly without worry about much

Scenario

https://sites.google.com/site/greateindiaclub/mobil-apps/windows8/customwpfrichtextboxwithcolorchangeandhighlightfunctionality

source code:

https://github.com/boobalaninfo/CustomRichTextBoxWithHighligh

Answer 3

I think you are looking for ScintillaNET.

On the other hand if you want to do this by yourself in RTB then you can do it by first finding the lineNumber using TextBoxBase.Lines property. Then ...

//Select the line from it's number
startIndex = richTextBox.GetFirstCharIndexFromLine(lineNumber);
richTextBox.Select(startIndex, length);

//Set the selected text fore and background color
richTextBox.SelectionColor = System.Drawing.Color.White;
richTextBox.SelectionBackColor= System.Drawing.Color.Blue;