WPF 保存文件

private void button2_Click(object sender, RoutedEventArgs e)
        {
            var saveFileDialog1 = new SaveFileDialog
            {
                Filter = "JPeg Image|*.jpg|Bitmap Image|*.bmp|Gif Image|*.gif",
                Title = "Save File"
            };
            saveFileDialog1.ShowDialog();

            if (!string.IsNullOrEmpty(saveFileDialog1.FileName)) return;
            using (var sw = new StreamWriter(saveFileDialog1.FileName))
            {
                sw.Write("Writing Text ");
                sw.WriteLine("Here we go.");
                sw.WriteLine("-------------------");
                sw.Write("Today is is: " + DateTime.Now);
                sw.WriteLine("Done");
            }
        }