if (someObj)C# null testing
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Sometimes it's the little things that really get to you. Right now, I'm getting really sick of typing " != null" in C#. This seems to be a very common test in C# (checking if someone has subscribed to an event, testing for a SelectedItem, the result of a find), so couldn't they have let you do a C++ style
Potentially of value may be the ?? null coalescing operator.
EDIT: Actually, I see this won't be particularly useful in the examples you give, but it's still handy to have.
EDIT: Actually, I see this won't be particularly useful in the examples you give, but it's still handy to have.
Author
Thanks, Unbeliever, but I'm afraid that doesn't help.
The ?? null coalescing operator is basically a shortcut for the ?: ternary op, which means that both operands must be of the same type, i.e. you can't do
anymore than you can do
The ?? null coalescing operator is basically a shortcut for the ?: ternary op, which means that both operands must be of the same type, i.e. you can't do
void SomeMethod(){}someObject ?? SomeMethod();anymore than you can do
someObject != null ? SomeMethod() : SomeOtherMethod()
In C#, it's that way because of a case like this:
Semantically, the expression with a typo will reduce to "if (object)", exactly like your example for testing against null. Since C# requires that the expression inside an "if" reduce to a boolean, instead of getting a runtime error, you get a compile-time error.
You could try bypassing this in C# 3.0 with an implicit typecast operator as an extension method, but I suspect those are specifically disallowed.
object a;object b;// something to one or both of the objectsif (a == b)// now what happens if you have a typo:if (a = b)Semantically, the expression with a typo will reduce to "if (object)", exactly like your example for testing against null. Since C# requires that the expression inside an "if" reduce to a boolean, instead of getting a runtime error, you get a compile-time error.
You could try bypassing this in C# 3.0 with an implicit typecast operator as an extension method, but I suspect those are specifically disallowed.
Sorry, think you'll just have to get used to it. I have never found a way around it, which I think is good. Trust me, its not that bad - at least its specific on what you are checking. C# likes to make you say what you want, not just guess it and hope its right, and its worth it. Think of it this way - you may waste a little time writing out != or == null, but at least you'll save a lot more using the .NET framework and the GC. ^_^
If it's a user made class, and it makes sense, you can make an implicit casting operator to bool so if(foo){} works.
That said, you shouldn't. That behavior is specific to C, carried forward for compatibility reasons into C++ and promptly abandoned by anything since. nulls are far less common in a language like C# that forces initialization before use and promotes exceptions for exceptional circumstances (and null coalescing where appropriate).
Though yeah, invoking an unsubscribed/null event should be a no-op...
That said, you shouldn't. That behavior is specific to C, carried forward for compatibility reasons into C++ and promptly abandoned by anything since. nulls are far less common in a language like C# that forces initialization before use and promotes exceptions for exceptional circumstances (and null coalescing where appropriate).
Though yeah, invoking an unsubscribed/null event should be a no-op...
I am trying to why you are having to do so much testing for null. I very rarely have to do this. So I am thinking there might be something about your design that is causing the need for this.
theTroll
theTroll
You have a null test whenever you implement your own object.Equals() override. It's not that uncommon.
I don't know of a shorter test, but I'm often even using object.ReferenceEquals(x, null) instead of x != null in order to avoid calling the operator != override. I guess that's just something you'll have to accept when programming in C#.
I don't know of a shorter test, but I'm often even using object.ReferenceEquals(x, null) instead of x != null in order to avoid calling the operator != override. I guess that's just something you'll have to accept when programming in C#.
Quote:Original post by ChaosEngineand cast null to false?if (someObj)
I don't see why this would be a problem.
What if someObj is a bool? now you need extra checks to see if it is either null or false ( if (someObj != true) if (someObj != null) [false] else [null])
Quote:Original post by KoobazaurQuote:Original post by ChaosEngineand cast null to false?if (someObj)
I don't see why this would be a problem.
What if someObj is a bool? now you need extra checks to see if it is either null or false ( if (someObj != true) if (someObj != null) [false] else [null])
bools are not nullable.
A class which is implicitly convertible to bool will handle the null case.
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