Intersect list returning null

Question

I have two List<FileInfo> , and I want to return a common FileItem between them.

 List<FileInfo> outputList = new List<FileInfo>(); outputList = list1.Intersect(list2).ToList(); 

However, I am returning an empty list.

Both lists contain FileInfo found

 System.IO.DirectoryInfo dir = new System.IO.DirectoryInfo(startFolder); IEnumerable<System.IO.FileInfo> fileList = dir.GetFiles("*.*", System.IO.SearchOption.AllDirectories); 

And it is filtered by requests.

Answer 1

I suspect that FileInfo does not override Equals / GetHashCode , so two different objects will be unequal, even if they refer to the same file. Three options:

• Convert lists to paths if you don't need them, like FileInfo
• Create an IEqualityComparer<FileInfo> and go to Intersect
• Add IntersectBy in the same style as DistinctBy in MoreLINQ and offer it as a patch for the project :) (I thought we already had this, but apparently not ...)

Answer 2

The links to FileInfo objects in your two lists will be different, so Intersect will create an empty list.

You will need to create a class that implements the IEqualityComparer<FileInfo> interface and passes an instance of this class to Intersect to get the expected result.