Question

I am busy writing my own collection type and need to have a function
Max that returns the value in the collection, where one of the value attributes is a max or some condition holds.

So I am trying to call Max(Func<…) on one of the underlying .net collections, but
I can’t seem to get it to work:

public TValue MaxValue(Func<TValue,TValue> func)
{
  return this.valueSet.Max<TValue>(func);
}

but I am getting 2 errors:

Argument 2: cannot convert from 'System.Func<TValue,TValue>' to System.Func<TValue,int>'

and

'System.Collections.Generic.SortedSet<TValue>' does not contain a definition for 'Max'
 and the best extension method overload 'System.Linq.Enumerable.Max<TSource>(System.Collections.Generic.IEnumerable<TSource>,
System.Func<TSource,int>)' has some invalid arguments

I just can’t seem to figure out what I should be doing here…

Answer 1

When you call:

this.valueSet.Max<TValue>(func);

the compiler interprets this as one of the Max overloads with one generic type. Either explicitly point out that the return value also should be a TValue type:

this.valueSet.Max<TValue, TValue>(func);

or use implicit typing and let the compiler sort out the types itself:

this.valueSet.Max(func);