你也可以从文本文件中读取文本到字符串，如下所示

string str = "";
StreamReader sr = new StreamReader(Application.StartupPath + "\\Sample.txt");
while(sr.Peek() != -1)
{
  str = str + sr.ReadLine();
}

你也可以从文本文件中读取文本到字符串，如下所示

string str = "";
StreamReader sr = new StreamReader(Application.StartupPath + "\\Sample.txt");
while(sr.Peek() != -1)
{
  str = str + sr.ReadLine();
}

看一下File.ReadAllText()方法

一些重要备注:

This method opens a file, reads each line of the file, and then adds each line as an element of a string. It then closes the file. A line is defined as a sequence of characters followed by a carriage return ('\r'), a line feed ('\n'), or a carriage return immediately followed by a line feed. The resulting string does not contain the terminating carriage return and/or line feed. This method attempts to automatically detect the encoding of a file based on the presence of byte order marks. Encoding formats UTF-8 and UTF-32 (both big-endian and little-endian) can be detected. Use the ReadAllText(String, Encoding) method overload when reading files that might contain imported text, because unrecognized characters may not be read correctly. The file handle is guaranteed to be closed by this method, even if exceptions are raised

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);
    }
}

string content = System.IO.File.ReadAllText( @"C:\file.txt" );

string text = File.ReadAllText("Path");一个字符串变量中包含了所有文本。如果你需要每一行单独，你可以使用这个:

string[] lines = File.ReadAllLines("Path");