你可以使用:

 public static void ReadFileToEnd()
{
    try
    {
    //provide to reader your complete text file
        using (StreamReader sr = new StreamReader("TestFile.txt"))
        {
            String line = sr.ReadToEnd();
            Console.WriteLine(line);
        }
    }
    catch (Exception e)
    {
        Console.WriteLine("The file could not be read:");
        Console.WriteLine(e.Message);
    }
}

用最少的c#代码最快的方法可能就是这个:

string readText = System.IO.File.ReadAllText(path);

你可以使用:

 public static void ReadFileToEnd()
{
    try
    {
    //provide to reader your complete text file
        using (StreamReader sr = new StreamReader("TestFile.txt"))
        {
            String line = sr.ReadToEnd();
            Console.WriteLine(line);
        }
    }
    catch (Exception e)
    {
        Console.WriteLine("The file could not be read:");
        Console.WriteLine(e.Message);
    }
}

File怎么样?ReadAllText:

string contents = File.ReadAllText(@"C:\temp\test.txt");

对于那些觉得这个东西有趣和有趣的新手来说，在大多数情况下(根据这些基准测试)将整个文件读入字符串的最快方法是通过以下方法:

using (StreamReader sr = File.OpenText(fileName))
{
        string s = sr.ReadToEnd();
}
//you then have to process the string

然而，绝对最快的读取文本文件的整体似乎是以下:

using (StreamReader sr = File.OpenText(fileName))
{
        string s = String.Empty;
        while ((s = sr.ReadLine()) != null)
        {
               //do what you have to here
        }
}

与其他几种技术相比，它在大多数情况下胜出，包括与BufferedReader的竞争。

你可以这样用

public static string ReadFileAndFetchStringInSingleLine(string file)
    {
        StringBuilder sb;
        try
        {
            sb = new StringBuilder();
            using (FileStream fs = File.Open(file, FileMode.Open))
            {
                using (BufferedStream bs = new BufferedStream(fs))
                {
                    using (StreamReader sr = new StreamReader(bs))
                    {
                        string str;
                        while ((str = sr.ReadLine()) != null)
                        {
                            sb.Append(str);
                        }
                    }
                }
            }
            return sb.ToString();
        }
        catch (Exception ex)
        {
            return "";
        }
    }

希望这对你有所帮助。