C#文件与字符串操作笔记

一：文件操作

1：判断文件是否存在

      if (File.Exists("文件名称"))
      {

                 //存在

      }

     else

      {

//不存在

      }

2:创建文件

FileStream fs = new FileStream("文件名称", FileMode.Create);

3:打开已存在文件

FileStream fs = File.Open("文件名称", FileMode.Open);

4:文件写入流

StreamWriter sw = new StreamWriter(fs);

5:文件读取流

StreamReader sr = new StreamReader("ipconfig.ini");

6:清空文件内容

fs.SetLength(0);

7:写入文件内容

sw.Write("写入的数据内容");

8:读取文件全部内容

string data = sr.ReadToEnd();

9:清空缓冲区

sw.Flush();

10:关闭流

sw.Close();

fs.Close();

二：字符串操作

1:获取字符串中指定字符的位置

字符串..IndexOf("指定字符")；

2:截取字符串两个位置之间的字符串

得到的字符串=data.Substring(开始位置, 结束位置);

3：用正则表达式获取开始和结束字符串中间的值

/// <summary>
/// 获得字符串中开始和结束字符串中间得值
/// </summary>
/// <param name="str">字符串</param>
/// <param name="s">开始</param>
/// <param name="e">结束</param>
/// <returns></returns> 
public static string GetValue(string str, string s, string e)
{
Regex rg = new Regex("(?<=(" + s + "))[.\\s\\S]*?(?=(" + e + "))", RegexOptions.Multiline | RegexOptions.Singleline);
return rg.Match(str).Value;
}

三:代码应用展示

 public partial class SystemSet : Page
    {
        public SystemSet()
        {
            InitializeComponent();
        }
        ///加载界面调用
        private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            if (File.Exists("ipconfig.ini"))//如果存在文件就加载文件内容
            {
                int posS, posE;
                string data,s1;
                StreamReader sr = new StreamReader("ipconfig.ini");
                //读取文件全部内容
                data = sr.ReadToEnd();
                //获取本地IP:后处在字符串的位置
                posS = data.IndexOf(":")+1;
                //获取结束位置
                posE = data.IndexOf("\r\n");
                //提取显示本地IP
                s1 = data.Substring(posS, posE - posS);
                textLocalIP.Text = s1;
                //去除本地IP后的内容
                data = data.Substring(posE+2);
                //本地端口
                posS = data.IndexOf(":") + 1;
                posE = data.IndexOf("\r\n");
                s1 = data.Substring(posS, posE - posS);
                textLocalPort.Text = s1;
                data = data.Substring(posE + 2);
                //目的IP
                posS = data.IndexOf(":") + 1;
                posE = data.IndexOf("\r\n");
                s1 = data.Substring(posS, posE - posS);
                textPurpostIP.Text = s1;
                data = data.Substring(posE + 2);
                //目的端口
                posS = data.IndexOf(":") + 1;
                posE = data.IndexOf("\r\n");
                s1 = data.Substring(posS, posE - posS);
                textPurpostPort.Text = s1;
                sr.Close();
                
            }
        }
        /// IP保存
        private void IPSave_Click(object sender, RoutedEventArgs e)
        {
            if (File.Exists("ipconfig.ini"))
            {
                //存在文件
                FileStream fs = File.Open("ipconfig.ini", FileMode.Open);
                StreamWriter sw = new StreamWriter(fs);
                //先清空文件内容
                fs.SetLength(0);
                //开始写入
                sw.Write("LocalIP:" + textLocalIP.Text + "\r\n");
                sw.Write("LocalPort:" + textLocalPort.Text + "\r\n");
                sw.Write("PurpostIP:" + textPurpostIP.Text + "\r\n");
                sw.Write("PurpostPort:" + textPurpostPort.Text + "\r\n");
                //清空缓冲区
                sw.Flush();
                //关闭流
                sw.Close();
                fs.Close();
            }
            else
            {
                FileStream fs = new FileStream("ipconfig.ini", FileMode.Create);
                StreamWriter sw = new StreamWriter(fs);
                //开始写入
                sw.Write("LocalIP:"+ textLocalIP.Text+"\r\n");
                sw.Write("LocalPort:" + textLocalPort.Text + "\r\n");
                sw.Write("PurpostIP:" + textPurpostIP.Text + "\r\n");
                sw.Write("PurpostPort:" + textPurpostPort.Text + "\r\n");
                //清空缓冲区
                sw.Flush();
                //关闭流
                sw.Close();
                fs.Close();
            }
            MessageBox.Show("IP参数保存成功!", "提示");
        }
    }