如何为下一个要写入的文本设置RichTextBox字体？

// 设置字体
FontFamily fontFamily = new FontFamily("Arial");
double fontSize = 14;
FontWeight fontWeight = FontWeights.Bold;

// 创建字体样式
FontStyle fontStyle = new FontStyle();
fontStyle.FontFamily = fontFamily;
fontStyle.FontSize = fontSize;
fontStyle.FontWeight = fontWeight;

// 将字体样式应用于 RichTextBox
RichTextBox richTextBox = new RichTextBox();
richTextBox.FontFamily = fontFamily;
richTextBox.FontSize = fontSize;
richTextBox.FontWeight = fontWeight;