使用OpenFileDialog选择文件

       ///

        /// 浏览文件
        ///

        ///
        ///
private void btnOpenFileDialog_Click(object sender, EventArgs e)
{ 

          OpenFileDialog ofd = new OpenFileDialog();
            ofd.RestoreDirectory = true;
            ofd.Title = "打开(Open)";
            ofd.FileName = "";
            ofd.InitialDirectory = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);//为了获取特定的系统文件夹，可以使用System.Environment类的静态方法GetFolderPath()。该方法接受一个Environment.SpecialFolder枚举，其中可以定义要返回路径的哪个系统目录
            ofd.Filter = "文本文件(*.txt)|*.txt";
            ofd.ValidateNames = true;     //文件有效性验证ValidateNames，验证用户输入是否是一个有效的Windows文件名
            ofd.CheckFileExists = true;   //验证路径有效性
            ofd.CheckPathExists = true;   //验证文件有效性
            try
            {
                if (ofd.ShowDialog() == DialogResult.OK)
                {
                    string fileNamePath = ofd.FileName;
                    this.txtFileName.Text = fileNamePath;
                    btnDownLoadBySelectFile.Enabled = true;
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message.ToString());
            }

}