private void button1_Click(object sender, EventArgs e){OpenFileDialog openFileDialog1 = new OpenFileDialog();openFileDialog1.Filter = "文本文件(*.txt)|*.txt|(*.rtf)|*.rtf";if (openFileDialog1.ShowDialog() == DialogResult.OK){StreamReader sr = new StreamReader(openFileDialog1.FileName, Encoding.Default);richTextBox1.Text = sr.ReadToEnd();sr.Close();}}

private void 打开文本文件ToolStripMenuItem_Click(object sender, EventArgs e)  {  string Filename;  pictureBox1.Visible = false;  if (this.openFileDialog1.ShowDialog() == DialogResult.OK)  {  Filename = openFileDialog1.FileName;  if (Filename != "")  {  this.textBox1.Text = Filename;  this.richTextBox1.LoadFile(@Filename, RichTextBoxStreamType.PlainText);  }  }  }

// Create a simple FlowDocument to serve as content.
FlowDocument flowDoc = new FlowDocument(new Paragraph(new Run("Simple FlowDocument")));
// Create an empty, default RichTextBox.
RichTextBox rtb = new RichTextBox();
// This call sets the contents of the RichTextBox to the specified FlowDocument.
rtb.Document = flowDoc;
// This call gets a FlowDocument representing the contents of the RichTextBox.
FlowDocument rtbContents = rtb.Document;

public static void LoadFromRTF(this RichTextBox richTextBox, string rtf){if (string.IsNullOrEmpty(rtf)){throw new ArgumentNullException();}TextRange textRange = new TextRange(richTextBox.Document.ContentStart, richTextBox.Document.ContentEnd);using (MemoryStream ms = new MemoryStream()){using (StreamWriter sw = new StreamWriter(ms)){sw.Write(rtf);sw.Flush();ms.Seek(0, SeekOrigin.Begin);textRange.Load(ms, DataFormats.Rtf);}}}

public void LoadText(){string textFile = @"\Win\WPFDemo\WPFDemo\Resource\1.txt";FileStream fs;if (File.Exists(textFile)){fs = new FileStream(textFile, FileMode.Open, FileAccess.Read);using (fs){TextRange text = new TextRange(richTextBox1.Document.ContentStart, richTextBox1.Document.ContentEnd);text.Load(fs, DataFormats.Text);}}}