What advantages does using var have over the explicit type in C#? [duplicate]

Answer 1

I like it, especially in unit tests, because as the code evolves I only have to fix up the right-hand side of the declaration/assignment. Obviously I also have to update to reflect the changes in usage, but at the point of declaration I only have to make one change.

Answer 2

You can abstract away the mental complexity of the technicalities to focus purely on the problem domain from your model. you have to make sure your variables are named meaningfully tho.

Answer 3

There aren't any real differences. Some people suggest using the explicit type because it can make maintaining the code easier. However, people that push for var have the stance that "if we use var, we are forced to use good naming conventions".

Of course if you use vars with the intention of having good naming conventions and that breaks down, it's more painful down the road. (IMO)

Answer 4

public IAwesome { string Whatever { get; } }
public SoCool : IAwesome { public string Whatever { get; } }

public HeyHey
{
    public SoCool GetSoCool() { return new SoCool(); }

    public void Processy()
    {
        var blech = GetSoCool();
        IAwesome ohYeah = GetSoCool();
        // Now blech != ohYeah, so var is blech and ohYeah is IAwesome.
    }
}

Answer 5

Besides the readability aspect you mentioned, 'var' also has the benefit of reducing the probability that a trivial code change will break other parts of your code. If you rename a type, for example. Or if you switch to a different type that is mostly compatible with the former type (e.g. changing from Foo[] to IEnumerable) you have much less work to do to get your code back to a compilable state.

Answer 6

It produces no meaningful change in the emitted IL. It is merely a code style preference.

I, for one, like it, especially when dealing with types that have long, generic, almost unreadable names such as Dictionary<string, IQueryable<TValue1, TValue2>>[].