用C#实现LINQ中的交集方法

Question

我正在尝试从两个文件夹中使用Intersect方法获取相同的文件。123.xml文件在所有文件夹中都是相同的(内容、日期、大小没有变化)。

Scores\Content\123.xml
Scores\Content\hi.xml
Scores\123.xml

Power\Content\123.xml
Power\Content\helo.xml
Power\123.xml

这段代码来自C#代码

        System.IO.DirectoryInfo dir1 = new System.IO.DirectoryInfo(path1);
        System.IO.DirectoryInfo dir2 = new System.IO.DirectoryInfo(path2);

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

        FileCompare myFileCompare = new FileCompare();

        bool areIdentical = list1.SequenceEqual(list2, myFileCompare);

        if (areIdentical == true)
        {
            Console.WriteLine("the two folders are the same");
        }
        else
        {
            Console.WriteLine("The two folders are not the same");
        }


        var queryCommonFiles = list1.Intersect(list2, myFileCompare);

queryCommonFiles只从Content文件夹返回123.xml，而不是其他文件夹。

这是来自FileCompare的代码

class FileCompare : System.Collections.Generic.IEqualityComparer<System.IO.FileInfo>
{

    public FileCompare() { }

    public bool Equals(System.IO.FileInfo f1, System.IO.FileInfo f2)
    {
        return (f1.Name == f2.Name &&
                f1.Length == f2.Length);
    }

    // Return a hash that reflects the comparison criteria. According to the 
    // rules for IEqualityComparer<T>, if Equals is true, then the hash codes must
    // also be equal. Because equality as defined here is a simple value equality, not
    // reference identity, it is possible that two or more objects will produce the same
    // hash code.
    public int GetHashCode(System.IO.FileInfo fi)
    {
        string s = String.Format("{0}{1}", fi.Name, fi.Length);
        return s.GetHashCode();
    }

}

编辑：

var queryList1Only = (from file in list1
                                  select file).Except(list2, myFileCompare);

            Console.WriteLine("The following files are in list1 but not list2:\n");
            foreach (var v in queryList1Only)
            {
                Console.WriteLine(v.FullName);
            }


            var queryList2Only = (from file in list2
                                  select file).Except(list1, myFileCompare);

            Console.WriteLine("The following files are in list2 but not list1:\n");
            foreach (var v in queryList2Only)
            {
                Console.WriteLine(v.FullName);
            }

这将为list1生成hi.xml，为list2生成helo.xml。正如我所说的，对于intersect方法，只有一个123.xml。

如有任何建议，我们将不胜感激

谢谢,

Answer 1

我刚刚更改了Equals方法以达到预期的结果。

class FileCompare : System.Collections.Generic.IEqualityComparer<System.IO.FileInfo>
    {

        public FileCompare() { }

        public bool Equals(System.IO.FileInfo f1, System.IO.FileInfo f2)
        {
            return (f1.Name == f2.Name && f1.Directory.Name == f2.Directory.Name && 
                    f1.Length == f2.Length);
        }

        // Return a hash that reflects the comparison criteria. According to the 
        // rules for IEqualityComparer<T>, if Equals is true, then the hash codes must
        // also be equal. Because equality as defined here is a simple value equality, not
        // reference identity, it is possible that two or more objects will produce the same
        // hash code.
        public int GetHashCode(System.IO.FileInfo fi)
        {
            string s = String.Format("{0}{1}", fi.Name, fi.Length);
            return s.GetHashCode();
        }

    }

Answer 2

一切看起来都很好。确保Scores\123.xml和Power\123.xml的长度相同。

Answer 3

因为您只使用FileInfo.Name和FileInfo.Length进行比较，所以Content\123.xml与123.xml相同(假设两个文件具有相同的大小，我猜测试数据也是如此)。

因此，就您的FileCompare类而言，您的输入集合包含重复项。根据MSDN，Intersect计算每个集合中的不同的元素。