Syntax Choice For Type Parameter Variance In C# And VB

Apr 12, 2010

In both C# and VB, type parameter modifiers are used to express the variance of type parameters. For example, the C# version looks like:

[Code]....

Since variance specifications basically restrict where and how a type parameter can be used, I tend to think of them as additional constraints on type parameters. I'm just curious as to why they aren't represented so. I mean, why are they represented in both languages as additional modifiers on type parameters, instead of being added to the type constraint list? If they were type constraints, the C# version would've looked like:

[Code]....

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