如何显示字典的结果值<string, string>来自 LINQ 语句

Question

I'm struggling and unable to display the results2 of my Dictionary<string, string> files

Dictionary<string, string> files = new Dictionary<string, string>();
foreach (var file in Directory.GetFiles(filepath + "\\Saved Pictures\\", "*.jpg"))
{
    files.Add(file, CalculateHash(file));
}

var duplicates = files.GroupBy(item => item.Value).Where(group => group.Count() > 1);


var results2 = duplicates.Select(group => group.GroupBy(x => x.Value));

So far I have tried :

foreach (KeyValuePair<string, string> result in results2)
{
    Console.WriteLine("Key: {0}, Value: {1}", result.Key, result.Value);
}

And I'm encountering this error message:

Cannot convert type 'System.Collections.Generic.IEnumerable<System.Linq.IGrouping<string, System.Collections.Generic.KeyValuePair<string, string>>>' to 'System.Collections.Generic.KeyValuePair<string, string>`

What I am doing wrong?

Answer 1

The error message tells you exactly what's wrong. results2 is not an IEnumerable<KeyValuePair<string, string>> as you'd assume in the foreach loop, but a more complex type, an IEnumrable<IGrouping<string, KeyValuePair<string, string>>> .

Two nested foreach loops will do it:

foreach (var grouping in results2)
{
    foreach (var pair in grouping)
    {
        // pair is a KeyValuePair<string, string>
    }
}

Answer 2

The more I look at this code the less I understand it. What is the point of grouping already grouped values by the same property they were originally grouped by?

In plain English, I suspect you are simply trying to obtain a list of all sets of files with identical hashes. A simple way to do this is:

var files = Directory.GetFiles(filepath + "\\Saved Pictures\\", "*.jpg");

// An enumerable of enumerables of files that share the same hash
var dupes = files.GroupBy(CalculateHash).Where(g => g.Count() > 1);

If you need to flatten this for display purposes, you can do:

// IEnumerable<(string hash, string file)>
var flattened = dupes.SelectMany(grp => grp.Select(file => (hash: grp.Key, file)));

foreach ((var hash, var file) in flattened)
{
    Console.WriteLine($"Key: {hash}, Value: {file}");
}