使用filestream读取文件

            //读取文本文件
           FileStream fs = new FileStream(filename, FileMode.Open, FileAccess.Read);
           //读取字节流
           StreamReader sr = new StreamReader(fs);
           //指定从开头读取文件
           sr.BaseStream.Seek(0, SeekOrigin.Begin);
           string ModelCont = sr.ReadToEnd();
           sr.Close();
           fs.Close();
           return ModelCont;