C# 读取大文件 （可以读取3GB大小的txt文件）

源代码样例：

1，读取一般文件的代码

 public static string ReaderFile(string path)
         {
             string fileData = string.Empty;
             try
             {   ///读取文件的内容
                 StreamReader reader = new StreamReader(path, Encoding.Default);
                 fileData = reader.ReadToEnd();
                 reader.Close();
             }
             catch (Exception ex)
             {
                 // throw new Exception(ex.Message,ex);
             }  ///抛出异常
             return fileData;
         }

2, 读取 大文件（大到约4个GB的文本文件）

 private bool ReadBigFile()
         {
             string sTmpFile=@"c:\tmpTest.txt";
             if (File.Exists(sTmpFile))
             {
                 File.Delete(sTmpFile);
             }

             if (!System.IO.File.Exists(sTmpFile))
             {
                 FileStream fs;
                 fs = File.Create(sTmpFile);
                 fs.Close();
             }

             if (!File.Exists(txtFileName.Text.Trim()))
             {
                 lblResult.Text = "File not exist!";
                 txtFileName.Focus();
                 return false;
             }

             FileStream streamInput = System.IO.File.OpenRead(@txtFileName.Text.Trim());
             FileStream streamOutput = System.IO.File.OpenWrite(sTmpFile);

             int iRowCount = 10;
             int.TryParse(txtRowCount.Text.Trim(), out iRowCount);

             try
             {
                 for (int i = 1; i <= iRowCount; )
                 {
                     int result = streamInput.ReadByte();
                     if (result == 13)
                     {
                         i++;
                     }
                     if (result == -1)
                     {
                         break;
                     }
                     streamOutput.WriteByte((byte)result);
                 }
             }
             finally
             {
                 streamInput.Dispose();
                 streamOutput.Dispose();
             }

             string sContent = ReaderFile(sTmpFile);
             CopyToClipboard(sContent);

             return true;
         }

         public static string ReaderFile(string path)
         {
             string fileData = string.Empty;
             try
             {   ///读取文件的内容
                 StreamReader reader = new StreamReader(path, Encoding.Default);
                 fileData = reader.ReadToEnd();
                 reader.Close();
             }
             catch (Exception ex)
             {
                 // throw new Exception(ex.Message,ex);
             }  ///抛出异常
             return fileData;
         }

         private void CopyToClipboard(string sSource)
         {
             Clipboard.Clear();
             if (!string.IsNullOrEmpty(sSource))
             {
                 Clipboard.SetText(sSource);
             }
         }