private string getLast50()
        {
            string strSol=string.Empty;
            List<string> listFile=new List<string>();
            StreamReader objSr =new StreamReader(@"c:\ss.txt",Encoding.Default);
            while(!objSr.EndOfStream){
                listFile.Add(objSr.ReadLine());
            }
            if(listFile.Count>50)
            {
                for (int i = listFile.Count - 50; i < listFile.Count-1; i++)
                {
                    strSol+=listFile[i]+Environment.NewLine;
                }
            }else
                for(int i=0;i<listFile.Count;i++)
                {
                    strSol+=listFile[i]+Environment.NewLine;
                }
            return strSol + listFile[listFile.Count-1];
        }

------解决方案--------------------

对1楼的程序的修改:

       private string getLast50()
       {
           string strSol=string.Empty;
           List<string> listFile=new List<string>();
           StreamReader objSr =new StreamReader(@"c:\ss.txt",Encoding.Default);
          
          
           while(!objSr.EndOfStream){
               listFile.Add(objSr.ReadLine());
               if ( listFile.Count > 50 )              // 如果多于50行,就把最前面的一行删掉
                   listFile.RemoveAt(0);
           }

           for(int i=0;i<listFile.Count;i++)
           {
               strSol+=listFile[i]+Environment.NewLine;
           }
           return strSol + listFile[listFile.Count-1];
       }


------解决方案--------------------
这种方式做聊天室你很快就会崩溃的。用个本地的sql express也行啊。

------解决方案--------------------
二进制方式读取，seek到最后往前缓冲区长度的地方，读到缓冲区，分析里面有多少换行符，不够的话，往前seek

------解决方案--------------------
思路被VMM说了。。。
参考如下代码：
C# code
FileStream vFileStream = new FileStream(@"c:\temp\temp.log", 
    FileMode.Open, FileAccess.Read);
byte[] vBuffer = new byte[0x1000];
int vReadLength;
int vLineCount = 0;
int vReadCount = 0;
int j = 0;
do
{
    vFileStream.Seek(-vBuffer.Length * ++vReadCount, SeekOrigin.End);
    vReadLength = vFileStream.Read(vBuffer, 0, vBuffer.Length);
    for (int i = vReadLength - 1; i >= 0; i--)
    {
        j++;
        if (vBuffer[i] == 10) vLineCount++;
        if (vLineCount >= 9)
        {
            if (vReadCount > 1)
            {
                vBuffer = new byte[vFileStream.Length - j - 1];
                vFileStream.Seek(j, SeekOrigin.End);
                vReadLength = vFileStream.Read(vBuffer, 0, vBuffer.Length);
                j = 0;
            }
            textBox1.Text = Encoding.Default.GetString(vBuffer, 
                vReadLength - j, j);
            break;
        }
    }
} while (vLineCount < 50 || vReadLength < vBuffer.Length);
if (vLineCount < 50)
    textBox1.Text = Encoding.Default.GetString(vBuffer, 0, vReadLength);
vFileStream.Close();
Text = vLineCount.ToString();

------解决方案--------------------

C# code

            string[] lines = File.ReadAllLines("C:\\test.txt", System.Text.Encoding.Default);//编码看你情况而定
            List<string> last50 = new List<string>();//也可以ArrayList last50=new ArrayList();
            for (int i = lines.Length - 1; i >= lines.Length - 50 && i >= 0; i--)
                last50.Insert(0, lines[i]);

------解决方案--------------------
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