LINQ Select Distinct Count in Lambda form

问题

Given a linq expression of an object collection 'items' such as this:

var total = (from item in items select item.Value).Distinct().Count()

Is it possible to convert this to use linq functions/lambdas:

items.Select(???).Distinct().Count()

回答1:

Use this:

items.Select(i => i.Value).Distinct().Count()

回答2:

It must be possible, since behind the scenes, LINQ is translated to lambdas and expression trees (at least LINQ to objects)

In your case the ??? part would be item => item.Value, i.e. for item, output item.value. So, the whole expression will be

var total = items.Select(item => item.Value).Distinct().Count();

来源：https://stackoverflow.com/questions/6609916/linq-select-distinct-count-in-lambda-form