C# winform 创建新文件--写入文本并另存为

private void button1_Click(object sender, EventArgs e)
        {
            Stream myStream;
            SaveFileDialog saveFileDialog1 = new SaveFileDialog();

            saveFileDialog1.Filter = "txt files (*.txt)|*.txt|All files (*.*)|*.*";
            saveFileDialog1.FilterIndex = 1;
            saveFileDialog1.RestoreDirectory = true;

            if (saveFileDialog1.ShowDialog() == DialogResult.OK)
            {
                if ((myStream = saveFileDialog1.OpenFile()) != null)
                {
                    using (StreamWriter sw = new StreamWriter(myStream))
                    {
                        // Add some text to the file.
                        sw.Write("This is the ");
                        sw.WriteLine("header for the file.");
                        sw.WriteLine("-------------------");
                        // Arbitrary objects can also be written to the file.
                        sw.Write("The date is: ");
                        sw.WriteLine(DateTime.Now);

                    }

                }
            }

        }