How to make some text bold in a rich text box in C#

问题

I want to create a text editor where I can make text bold, change its color, etc.

I found this code to approximately work:

public static void BoldSelectedText(RichTextBox control)
{
     control.SelectionFont = new Font(control.Font.FontFamily, control.Font.Size,         FontStyle.Bold);
}

But when I type in more letters in the RichTextBox the text is still bold.

How can I make it so that only the selected text is bold and the next characters aren't unless I select the text and hit the "Make Bold" button?

回答1:

You should set the font after the selection to the original font.

If you want you can save the SelectionStart and SelectionLength and call the Select method to select the text again.

// Remember selection
int selstart = control.SelectionStart;
int sellength = control.SelectionLength;

// Set font of selected text
// You can use FontStyle.Bold | FontStyle.Italic to apply more than one style
control.SelectionFont = new Font(control.Font, FontStyle.Bold);

// Set cursor after selected text
control.SelectionStart = control.SelectionStart + control.SelectionLength;
control.SelectionLength = 0;
// Set font immediately after selection
control.SelectionFont = control.Font;

// Reselect previous text
control.Select(selstart, sellength);

this way the text stays selected, and the font afterwards is still correct.

来源：https://stackoverflow.com/questions/7923919/how-to-make-some-text-bold-in-a-rich-text-box-in-c-sharp