富文本框具有一个名为Rtf的属性。将该属性设置为您的字符串值。另外，您的字符串的第一个字符还有多余的空格。在看到您的Hello World之前，我不得不将其删除。

Rich textbox has a property named Rtf. Set that property to your string value. Also, your string has an extra space as the first character. I had to remove that before I saw your Hello World.