C# 图片与BASE64编码互转实现

 //图片 转为    base64编码的文本
        private void button1_Click(object sender, EventArgs e)
        {
            OpenFileDialog dlg = new OpenFileDialog();
            dlg.Multiselect = true;
            dlg.Title = "选择要转换的图片";
            dlg.Filter = "Image files (*.jpg;*.bmp;*.gif;*.png)|*.jpg*.jpeg;*.gif;*.bmp|AllFiles (*.*)|*.*";
            if (DialogResult.OK == dlg.ShowDialog())
            {
                for (int i = 0; i < dlg.FileNames.Length; i++)
                {
                    ImgToBase64String(dlg.FileNames[i].ToString());
                }
            }
        }
        //图片 转为    base64编码的文本
        private void ImgToBase64String(string Imagefilename)
        {
            try
            {
                Bitmap bmp = new Bitmap(Imagefilename);
                this.pictureBox1.Image = bmp;
                FileStream fs = new FileStream(Imagefilename + ".txt", FileMode.Create);
                StreamWriter sw = new StreamWriter(fs);

                MemoryStream ms = new MemoryStream();
                bmp.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
                byte[] arr = new byte[ms.Length];
                ms.Position = 0;
                ms.Read(arr, 0, (int)ms.Length);