C# 打开、另存文件

以txt文件为例
打开文件选择框

private void btn_choose_Click(object sender, EventArgs e)
        {
            OpenFileDialog** InvokeDialog = new OpenFileDialog();
            InvokeDialog.Filter = "txt文件|*.txt";
            if (InvokeDialog.ShowDialog() == DialogResult.OK)
            {
                this.txt_path.Text = InvokeDialog.FileName;
                filepath = this.txt_path.Text;              
            }
        }

另存文件

private void btn_selRoute_Click(object sender, EventArgs e)
        {
            string localFilePath = "";
           SaveFileDialog  sfd = new SaveFileDialog();
            sfd.Filter= "txt文件（*.txt）|*.txt";
            sfd.FilterIndex= 1;
            sfd.RestoreDirectory= true;
            if (sfd.ShowDialog() == DialogResult.OK)
            {
                localFilePath = sfd.FileName.ToString();
                string fileNameExt = localFilePath.Substring(localFilePath.LastIndexOf("\") + 1);
                this.txt_saveRoute.Text = localFilePath;
            }
        }