StreamWriter sw = new StreamWriter(文件路径, true);
sw.Write(string类型的值);
sw.Dispose();

------解决方案--------------------

上面的改下
C# code
sw.WriteLine();
sw.Write(string类型的值);

------解决方案--------------------

 public void WriteLog(string conten)
       {
           try
           {
               //判断文件夹是否存在
               if (!this.CreateDirectoy())
               {
                   //如果不存在，停止
                   return;
               }
               //获取文件的名称,每天生成一个日志文件
               this.FixedLogFileName = DateTime.Now.ToString("yyyy-MM-dd") + this.FixedLogFileName;
               string content =DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss")+"\t"+conten +Environment.NewLine;
               File.AppendAllText(this.LogDirName + "\\" + this.FixedLogFileName, content);
           }
           catch (Exception ex)
           {
               throw new Exception(ex.ToString());
           }
       }

------解决方案--------------------

FileStream fs=new FileStream("xxxx",FileMode.Append,FileAccess.Write);

StreamWriter sw=new StramWriter(fs,Encoding.ASCII);

sw.WriteLine(strData);