文件操作——c#

private void btnOpen_Click(object sender, EventArgs e)
        {
            OpenFileDialog ofd = new OpenFileDialog();
            ofd.InitialDirectory = @"C:\Users\LWP1398\Desktop"; //设置初始路径
            ofd.Filter = "Excel文件(*.xls)|*.xls|Csv文件(*.csv)|*.csv|所有文件(*.*)|*.*"; //设置“另存为文件类型”或“文件类型”框中出现的选择内容
            ofd.FilterIndex = 2; //设置默认显示文件类型为Csv文件(*.csv)|*.csv
            ofd.Title = "打开文件"; //获取或设置文件对话框标题
            ofd.RestoreDirectory = true;
            if (ofd.ShowDialog() == DialogResult.OK)
            {
                //FileName：所选文件的全路径  SafeFileName：所选的文件名
                txtPath.Text = "FileName:" + ofd.FileName + "\r\n" + "SafeFileName:" + ofd.SafeFileName;
            }
        }

private void button3_Click(object sender, EventArgs e)
        {
            OpenFileDialog ofd = new OpenFileDialog();
            ofd.InitialDirectory = @"C:\Users\LWP1398\Desktop"; //设置初始路径
            ofd.Filter = "Excel文件(*.xls)|*.xls|Csv文件(*.csv)|*.csv|所有文件(*.*)|*.*"; //设置“另存为文件类型”或“文件类型”框中出现的选择内容
            ofd.FilterIndex = 2; //设置默认显示文件类型为Csv文件(*.csv)|*.csv
            ofd.Title = "打开文件"; //获取或设置文件对话框标题
            ofd.RestoreDirectory = true;设置对话框是否记忆上次打开的目录
 
            ofd.Multiselect = true;//设置多选
            if (ofd.ShowDialog() == DialogResult.OK)
            {
                for (int i = 0; i < ofd.FileNames.Length; i++)
                {
                    txtPath.Text += ofd.FileNames[i] + "\r\n";//输出一个路径回车换行
                }
                for (int i = 0; i < ofd.FileNames.Length; i++)
                {
                    txtPath.Text += ofd.SafeFileNames[i] + "\r\n";
                }
            }
        }

private void button2_Click(object sender, EventArgs e)
        {
            SaveFileDialog sfd=new SaveFileDialog();
            sfd.Filter = "文本文件(*.txt)|*.txt|所有文件|*.*";//设置文件类型
            sfd.FileName = "保存";//设置默认文件名
            sfd.DefaultExt = "txt";//设置默认格式（可以不设）
            sfd.AddExtension = true;//设置自动在文件名中添加扩展名
            if (sfd.ShowDialog()==DialogResult.OK)
            {
                txtPath.Text = "FileName:" + sfd.FileName + "\r\n" ;
                using (StreamWriter sw = new StreamWriter(sfd.FileName))
                {              
                    sw.WriteLineAsync("今天是个好天气");
                }
            }
            MessageBox.Show("ok");
        }

private void saveFileDialog1_FileOk(object sender, CancelEventArgs e)
{
     saveFileDialog1.AddExtension = true; //自动添加扩展名
     e.Cancel = true; //取消保存操作            
     string 扩展名 = System.IO.Path.GetExtension(saveFileDialog1.FileName);
     //判断扩展名并实现自定义的保存操作(导出)
     if (扩展名 == "txt")
     { }
     if (扩展名 == "xml")
     { }
}

string defaultPath = "";
FolderBrowserDialog dialog = new FolderBrowserDialog();
//打开的文件夹浏览对话框上的描述
dialog.Description = "请选择一个文件夹";
//是否显示对话框左下角 新建文件夹 按钮，默认为 true
dialog.ShowNewFolderButton = false;
//首次defaultPath为空，按FolderBrowserDialog默认设置（即桌面）选择
if (defaultPath != "")
{
    //设置此次默认目录为上一次选中目录
    dialog.SelectedPath = defaultPath;
}
//按下确定选择的按钮
if (dialog.ShowDialog() == DialogResult.OK)
{
    //记录选中的目录
    defaultPath = dialog.SelectedPath;
}
MessageBox.show(defaultPath);