c#文件相关笔记

1、将*.txt文件内容转换为一个字符串str

FileStream fs = new FileStream("路径\\*.txt", FileMode.Open);
StreamReader sr = new StreamReader(fs，Encoding.Default);
string str = sr.ReadToEnd();

2、将str写入*.txt

string str = "";
FileStream fsWrite = new FileStream("路径\\*.txt", FileMode.OpenOrCreate, FileAccess.Write);

StreamWriter sw = new StreamWriter(fsWrite，Encoding.Default);

sw.WriteLine(str);   
sw.Close();

3、将str追加到*.txt

string str="";

StreamWriter sw =File.AppendTex("路径\\*.txt");

sw.WriteLine(str);   
sw.Close();

 4、以文件流的方式打开或保存文件

private void btSelect_Click(object sender, EventArgs e)
        {
            using (OpenFileDialog ofd = new OpenFileDialog())
            {
                if (ofd.ShowDialog() != DialogResult.OK)
                {
                    return;
                }
                //读文件
              //string strRead=  File.ReadAllText(ofd.FileName, Encoding.Default); //小文件
                using (FileStream fs = new FileStream(ofd.FileName, FileMode.Open, FileAccess.Read))
                {
                    using (StreamReader sr = new StreamReader(fs))
                    {
                        while (!sr.EndOfStream)
                        {
                            string strLine = sr.ReadLine();
                            rbRead.Text += strLine;
                        }
                    }
                }
            }
        }

private void btSave_Click(object sender, EventArgs e)
        {
            using (SaveFileDialog sfd = new SaveFileDialog())
            {
                if (sfd.ShowDialog() != DialogResult.OK)
                {
                    return;
                }
                //File.WriteAllText(sfd.FileName,rbWrite.Text);  //小文件
                //using (StreamWriter sw = new StreamWriter(sfd.FileName, false, Encoding.Default, 1024 * 1024))
                //{
                //    sw.Write(rbWrite.Text);
                //    sw.Flush();
                //}
                using (FileStream fs = new FileStream(sfd.FileName, FileMode.OpenOrCreate, FileAccess.Write))
                {
                    string str=rbWrite.Text;
                    byte[] data=Encoding.Default.GetBytes(str);

                    fs.Write(data, 0, data.Length);
                }
            }
        }