/// <summary>
  /// 把预定内容导入到Text文档
  /// </summary>
  private void ChangeDbToText()

  { 
   this.RecNum.Visible=true;
   //建立文件，并打开
   string oneLine = "";
   string filename = "Storage Card/YD"+ DateTime.Now.ToString("yyyyMMddhhmmss")+".txt";
   FileInfo finfo = new FileInfo(filename);
   StreamWriter w = finfo.CreateText();
   w.BaseStream.Seek(0, SeekOrigin.End);   
   SqlCeCommand sqlTable = Mc.gConn.CreateCommand();
   sqlTable.CommandText = "select * from YDK ";
   SqlCeDataReader Dr=sqlTable.ExecuteReader();
   try
   {
    int i=0;
    while(Dr.Read())
    {
     //输出一条到文件
     oneLine = Dr["ISBN"].ToString().PadRight(20,' ')+Dr["BookNum"].ToString().PadRight(10,' ')+Dr["Rdate"].ToString().PadRight(10,' ')+"      "+Dr["ShuShang"].ToString().PadRight(10,' ');
     w.WriteLine(oneLine);
     i+=1;
     if(i%100==0)
     {
      this.RecNum.Text=i.ToString();
      this.RecNum.Refresh();
     }

    }
    //关闭文件
    w.Close();
 

    MessageBox.Show("成功导出"+i.ToString().Trim()+"条!");
    this.RecNum.Visible=false;
    Dr.Close();
   }
   catch
   {
    MessageBox.Show("未导出数据!");
    this.RecNum.Visible=false;
    Dr.Close();
   }
   
  }