austinsims / relevant-equals

C# extension methods to compare objects by specified properties only

These are two extension methods to Object that compare instances based on the values of a subset of their properties.

RelevantEquals

Given a class:

class F {
    public string Foo { get; set; }
    public string Bar { get; set; }
}

using RelevantEquals will yield the following results:

var a = new F { Foo = "Hello", Bar = "World" };
var b = new F { Foo = "Goodbye", Bar = "World" };

// true
a.RelevantEquals<F>(b, new Expression<Func<F, object>>[] {
    (f) => f.Bar
})

// false
a.RelevantEquals<F>(b, new Expression<Func<F, object>>[] {
    (f) => f.Foo,
    (f) => f.Bar
})

RelevantEquivalent

This is similar to CollectionAssert.AreEquivalent. It will return true if the two collections have the same instances as far as the specified properties go.

var things = new[] {
    new F { Foo = "English", Bar = "England"},
    new F { Foo = "Swedish", Bar = "Sweden"},
};

var slightlyDifferentThings = new[] {
    new F { Foo = "Anglisch", Bar = "England"},
    new F { Foo = "Svenska", Bar = "Sweden"},
};

// true
things.RelevantEquivalent<T>(slightlyDifferentThings, new Expression<Func<F, object>>[] {
    (f) => f.Bar
});

// false
things.RelevantEquivalent<F>(slightlyDifferentThings, new Expression<Func<F, object>>[] {
    (f) => f.Foo,
    (f) => f.Bar
});