Linq Group by在lambda表达式中

Question

I have Model follow list:

    Id                  Name
----------------------------------------------------
    1                   john
    1                   john
    1                   john
    2                   jennifer
    2                   jennifer
    3                   smith

I want to group that Model to show following result

    Id                  Name
----------------------------------------------------
    1                   john
    2                   jennifer
    3                   smith

Answer 1

If Model implements IEquatable<Model> then it's trivial:

var noDuplicates = list.Distinct();

If it does not make sense for Model to implement that interface, you can use this overload of Distinct that lets you specify the equality criteria on the side. The documentation for IEqualityComparer<T> has an example on how to implement such.

Answer 2

                ILookup<int, string> lookup =
                list
                .ToLookup(p => p.Id,
                          p => p.Name);

            foreach (IGrouping<int, string> group in lookup)
            {
                Console.WriteLine(group.Key);
                foreach (string name in group)
                    Console.WriteLine("    {0}", name);
            }

Answer 3

从模型组v中的v通过v.id到g选择g