如何在文件编码未知时使用ReadAllText

时间:2012-05-25 11:14:00

标签: c# .net encoding

我正在阅读 ReadAllText

的文件
    String[] values = File.ReadAllText(@"c:\\c\\file.txt").Split(';');

    int i = 0;

    foreach (String s in values)
    {
        System.Console.WriteLine("output: {0} {1} ", i, s);
        i++;
    }

如果我尝试阅读一些文件,有时候我会得到错误的字符(对于ÖÜÄ......)。输出就像'?',因为编码存在一些问题:

output: 0 TEST
output: 1 A??O?

一种解决方案是在ReadAllText中设置编码,让我们说ReadAllText(@"c:\\c\\file.txt", Encoding.UTF8)这样可以解决问题的方法。但是,如果我仍然会得到'?'作为输出?如果我不知道文件的编码怎么办?如果每个文件都有不同的编码怎么办?用c#做最好的方法是什么?谢谢

2 个答案:

答案 0 :(得分:7)

可靠地执行此操作的唯一方法是在文本文件的开头查找byte order marks。 (该blob更一般地表示所使用的字符编码的字节序,但也表示编码 - 例如UTF8,UTF16,UTF32)。不幸的是,这种方法仅适用于基于Unicode的编码,在此之前没有任何内容(必须使用更不可靠的方法)。

StreamReader类型支持检测这些标记以确定编码 - 您只需将标志传递给参数:

new System.IO.StreamReader("path", true)

然后,您可以检查stremReader.CurrentEncoding的值以确定文件使用的编码。但请注意,如果不存在字节编码标记,则CurrentEncoding将默认为Encoding.Default

Refer codeproject solution to detect encoding

答案 1 :(得分:5)

您必须先检查文件编码。试试这个

System.Text.Encoding enc = null; 
System.IO.FileStream file = new System.IO.FileStream(filePath, 
    FileMode.Open, FileAccess.Read, FileShare.Read); 
if (file.CanSeek) 
{ 
    byte[] bom = new byte[4]; // Get the byte-order mark, if there is one 
    file.Read(bom, 0, 4); 
    if ((bom[0] == 0xef && bom[1] == 0xbb && bom[2] == 0xbf) || // utf-8 
        (bom[0] == 0xff && bom[1] == 0xfe) || // ucs-2le, ucs-4le, and ucs-16le 
        (bom[0] == 0xfe && bom[1] == 0xff) || // utf-16 and ucs-2 
        (bom[0] == 0 && bom[1] == 0 && bom[2] == 0xfe && bom[3] == 0xff)) // ucs-4 
    { 
        enc = System.Text.Encoding.Unicode; 
    } 
    else 
    { 
        enc = System.Text.Encoding.ASCII; 
    } 

    // Now reposition the file cursor back to the start of the file 
    file.Seek(0, System.IO.SeekOrigin.Begin); 
} 
else 
{ 
    // The file cannot be randomly accessed, so you need to decide what to set the default to 
    // based on the data provided. If you're expecting data from a lot of older applications, 
    // default your encoding to Encoding.ASCII. If you're expecting data from a lot of newer 
    // applications, default your encoding to Encoding.Unicode. Also, since binary files are 
    // single byte-based, so you will want to use Encoding.ASCII, even though you'll probably 
    // never need to use the encoding then since the Encoding classes are really meant to get 
    // strings from the byte array that is the file. 

    enc = System.Text.Encoding.ASCII; 
}