求助：textbox保存后文本里面没有内容

如题，保存后文本文档里面没有东西，新手请教高手们如何解决，我的代码如下
private void SaveFile_Click(object sender, EventArgs e)
        {
            Stream myStream;
            string fileName = "Untitled";
            SaveFileDialog saveFileDialog1 = new SaveFileDialog();
            
            saveFileDialog1.InitialDirectory = "c:\\";
            saveFileDialog1.Filter = "txt files (*.txt)|*.txt|All files (*.*)|*.*";
            saveFileDialog1.FilterIndex = 2;
            saveFileDialog1.RestoreDirectory = true;

            if (saveFileDialog1.ShowDialog() == DialogResult.OK)
            {
                if ((myStream = saveFileDialog1.OpenFile()) != null)
                {
                    try
                    {
                        fileName = saveFileDialog1.FileName;
                        Stream stream = File.OpenWrite(fileName);
                        StreamWriter writer = new StreamWriter(fileName,false,Encoding.Default);
                        writer.Write(tbUserProgram.Text);
                        writer.Close();
                        stream.Close();
                        myStream.Close();
                    }
                    catch
                    { }

                }
            }

        }