除了Stream抽象类及其派生的实现类（如FileStream,MemoryStream,NetworkStream...）,为了简化流的操作，.net类库中还定义了TextReader和TextWriter抽象类，分别表示读取器和写入器。

（一）写入器的基类

TextWriter抽象类的官方定义如下：

（二）TextWriter的实现类之StreamWriter

继承Object->MarshalByRefObject->TextWriter->StreamWriter

可以通过构造函数（输入文件路径或者流实例对象）来直接创建StreamWriter实例,也可以通过File.CreateText()方法或File.AppendText()方法来得到StreamWriter实例。

static void Main(string[] args) { // Get the directories currently on the C drive. DirectoryInfo[] cDirs = new DirectoryInfo(@"c:\").GetDirectories(); // Write each directory name to a file. using (StreamWriter sw = new StreamWriter("CDriveDirs.txt")) { foreach (DirectoryInfo dir in cDirs) { sw.WriteLine(dir.Name); } } // Read and show each line from the file. string line = ""; using (StreamReader sr = new StreamReader("CDriveDirs.txt")) { while ((line = sr.ReadLine()) != null) { Console.WriteLine(line); } } }

（三）TextWriter的实现类之StringWriter

实现用于将信息写入字符串的 TextWriter。 信息存储在基础 StringBuilder 中。

using System; using System.IO; class StringRW { static void Main() { string textReaderText = "TextReader is the abstract base " + "class of StreamReader and StringReader, which read " + "characters from streams and strings, respectively.\n\n" + "Create an instance of TextReader to open a text file " + "for reading a specified range of characters, or to " + "create a reader based on an existing stream.\n\n" + "You can also use an instance of TextReader to read " + "text from a custom backing store using the same " + "APIs you would use for a string or a stream.\n\n"; Console.WriteLine("Original text:\n\n{0}", textReaderText); // From textReaderText, create a continuous paragraph // with two spaces between each sentence. string aLine, aParagraph = null; StringReader strReader = new StringReader(textReaderText); while(true) { aLine = strReader.ReadLine(); if(aLine != null) { aParagraph = aParagraph + aLine + " "; } else { aParagraph = aParagraph + "\n"; break; } } Console.WriteLine("Modified text:\n\n{0}", aParagraph); // Re-create textReaderText from aParagraph. int intCharacter; char convertedCharacter; StringWriter strWriter = new StringWriter(); strReader = new StringReader(aParagraph); while(true) { intCharacter = strReader.Read(); // Check for the end of the string // before converting to a character. if(intCharacter == -1) break; convertedCharacter = Convert.ToChar(intCharacter); if(convertedCharacter == '.') { strWriter.Write(".\n\n"); // Bypass the spaces between sentences. strReader.Read(); strReader.Read(); } else { strWriter.Write(convertedCharacter); } } Console.WriteLine("\nOriginal text:\n\n{0}", strWriter.ToString()); } }