class Abuse: Foo
{
    public override int GetHashCode() => 0;
}

class MyClass
{
    public int Key1 { get; set;}
    public int Key2 { get; set;}
 
    // other properties
}

struct MyClassCompositeKey
{
    public int Key1 { get; set;}
    public int Key2 { get; set;}

    public override int GetHashCode()
    {
        // override
    }

    public override bool Equals()
    {
        // override
    }
}