The Daily WTF

Submitter “NotAThingThatHappens” stumbled across a “unique” way to check for nulls in C#.

Now, there are already a few perfectly good ways to check for nulls. variable is null, for example, or use nullable types specifically. But “NotAThingThatHappens” found approach:

if(((object)someObjThatMayBeNull) is var _) { //object is null, react somehow } else { UseTheObjectInAMethod(someObjThatMayBeNull); }

What I hate most about this is how cleverly it exploits the C# syntax to work.

Normally, the _ is a discard. It’s meant to be used for things like tuple unpacking, or in cases where you have an out parameter but don’t actually care about the output- foo(out _) just discards the output data.

But _ is also a perfectly valid identifier. So var _ creates a variable _, and the type of that variable is inferred from context- in this case, whatever type it’s being compared against in someObjThatMayBeNull. This variable

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