Question

如果我比较两个文件而不对这些查询进行舍入分钟结果

var queryList1Only3 = (from file in list1 select file).Except(list2, myFileCompare2);
var queryList1Only33 = (from file in list2 select file).Except(list1, myFileCompare2);

是

12/14/2010 4:14:10 PM     C:\xml\Tracker.xml
10/13/2010 3:00:27 PM      D:\xml\Tracker.xml

但是如果我将日期时间缩短到分钟，则查询列表的结果为

   12/14/2010 4:14:10 PM     C:\xml\Tracker.xml

并且第二个查询只返回空，因为我只修改了C:\xml\Tracker.xml文件而另一个文件没有更改......

和

public class FileCompareLastwritetime : System.Collections.Generic.IEqualityComparer<System.IO.FileInfo>
        {
            public FileCompareLastwritetime() { }
            public bool Equals(System.IO.FileInfo f1, System.IO.FileInfo f2)
            {
                return RoundToMinute(f1.LastWriteTime) == RoundToMinute(f2.LastWriteTime);
            }
            public int GetHashCode(System.IO.FileInfo fi)
            {
               return RoundToMinute(fi.LastWriteTime).GetHashCode();
            }
        }


 public static DateTime RoundToMinute(DateTime time)
            {
                return new DateTime(time.Year, time.Month, time.Day,
                                    time.Hour, time.Minute, 0, time.Kind);
            }

有什么建议吗？

编辑：

   IEnumerable<System.IO.FileInfo> list1 = dir1.GetFiles("*.*", System.IO.SearchOption.AllDirectories);
   IEnumerable<System.IO.FileInfo> list2 = dir2.GetFiles("*.*", System.IO.SearchOption.AllDirectories);

Answer 1

DateTime equals比较Ticks，使用time.Year，time.Month等设置值时可能略有不同。我找到的最佳DateTime截断方法如下：

///<summary>
/// Extension methods for DateTime class
///</summary>
public static class DateTimeExt
{
    /// <summary>
    /// <para>Truncates a DateTime to a specified resolution.</para>
    /// <para>A convenient source for resolution is TimeSpan.TicksPerXXXX constants.</para>
    /// </summary>
    /// <param name="date">The DateTime object to truncate</param>
    /// <param name="resolution">e.g. to round to nearest second, TimeSpan.TicksPerSecond</param>
    /// <returns>Truncated DateTime</returns>
    public static System.DateTime Truncate(this System.DateTime date, long resolution)
    {
        return new System.DateTime(date.Ticks - (date.Ticks % resolution), date.Kind);
    }
}

用法：myDateTime.Truncate（TimeSpan.TicksPerMinute）截断为分钟。它没有圆，但你的例子也没有。

基于日期时间到分钟比较两个文件的问题？

1 个答案: