The Max() linq extension method on a List<MyClass> [Solved]

[TMattC]

Im not very good at LINQ (yet), but I understand that I by using the LINQ extension methods in the Enumerable class can do like this to get the largest value in the sequence:

List lst = new List() { 1,2,3,4,5,6,7,8 };
int max = lst.Max();

But what if my List looks like this?

public class MyClass
{
public int Id { get; set; }
public MyClass(int _id)
{ Id = _id; }
}

List lst = new List() { new MyClass(1), new MyClass(2), new MyClass(3) };

I want to get the Id value from the instance with the highest Id value. Im under the impression that I should write a MyClass method and pass it to the Max(...) extension method, but I cant seem to figure out how it would be done. Anyone?

[TMattC]

I solved it by myself, turned out it wasnt so complicated.

int m = lst.Max(mc => mc.Id);

[Richard Deeming]

If you only want the value of the maximum ID, you can use either:

int maxId = lst.Select(x => x.Id).Max();

or:

int maxId = lst.Max(x => x.Id);

If you want to get the instance of MyClass which has the maximum ID, you'll need to implement the IComparable<T> interface[^]:

public class MyClass : IComparable<MyClass>
{
public int Id { get; set; }

public MyClass(int \_id)
{ 
    Id = \_id; 
}

public int CompareTo(MyClass other)
{
    if (other == null) return 1;
    return Id.CompareTo(other.Id);
}

}
...
MyClass maxId = lst.Max();

Unfortunately, there isn't an overload which takes an IComparer<T> instance[^], so if you need different sort orders in different situations, you're stuck with writing your own Max method.

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