判断文件编码并且替换指定字符串的方法

 1 　　　　 private void Replace(string oldStr, string newStr, string file)
 2         {
 3             FileStream fs = File.OpenRead(file);
 4             //to know if this file is text file or binary file
 5             byte b;
 6             for (long i = 0; i < fs.Length; i++)
 7             {
 8                 b = (byte)fs.ReadByte();
 9                 if (b == 0)
10                 {
11                     MessageBox.Show("Not Text File");
12                     return;//if there is this byte then this is not text file。
13                 }
14             }
15             //Judge the type of encoding。
16             byte[] bytes = new byte[2];
17             Encoding coding = Encoding.Default;
18             if (fs.Read(bytes, 0, 2) > 2)
19             {
20                 if (bytes == new byte[2] { 0xFF, 0xFE }) coding = Encoding.Unicode;
21                 if (bytes == new byte[2] { 0xFE, 0xFF }) coding = Encoding.BigEndianUnicode;
22                 if (bytes == new byte[2] { 0xEF, 0xBB }) coding = Encoding.UTF8;
23             }
24             fs.Close();
25 
26             string text = File.ReadAllText(file,coding);
27             File.WriteAllText(file, text.Replace(oldStr, newStr), coding); 
28         }