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Why shouldn't I always use nullable types in C#

Asked 2009-05-06T16:50:47.427
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I've been searching for some good guidance on this since the concept was introduced in .net 2.0.

Why would I ever want to use non-nullable data types in c#? (A better question is why wouldn't I choose nullable types by default, and only use non-nullable types when that explicitly makes sense.)

Is there a 'significant' performance hit to choosing a nullable data type over its non-nullable peer?

I much prefer to check my values against null instead of Guid.empty, string.empty, DateTime.MinValue,<= 0, etc, and to work with nullable types in general. And the only reason I don't choose nullable types more often is the itchy feeling in the back of my head that makes me feel like it's more than backwards compatibility that forces that extra '?' character to explicitly allow a null value.

Is there anybody out there that always (most always) chooses nullable types rather than non-nullable types?

Thanks for your time,

c# null c#-2.0 nullable
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You seem to have 2 different questions...

Why would I ever want to use non-nullable data types in C#?

Simple, because the value-type data you're relying on is guaranteed by the compiler to actually have a value!

Why wouldn't I choose nullable types by default, and only use non-nullable types when that explicitly makes sense?

As Joel has already mentioned, a type can only be null if it is a reference type. Value types are guaranteed by the compiler to have a value. If your program depends on a variable to have a value, then this is the behavior you will want by not choosing a nullable type.

Of course, when your data is coming from anywhere that is not your program, then all bets are off. The best example is from a database. Database fields can be null, so you would want your program variable to mimic this value - not just create a "magic" value (i.e. -1, 0, or whatever) that "represents" null. You do this with nullable types.

answered 2009-05-06T17:01:21.363

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