What use is the Aliases property of assembly references in Visual Studio 8

c# visual-studio reference csproj
Spencer Booth picture Spencer Booth · Nov 13, 2008 · Viewed 41.2k times · Source

When I add an assembly reference to a project in Visual Studio 8 the Aliases property, of that reference, is set to "global". What is this property good for and why is it set to global?

MSDN tells me that this is a list of aliases for the assembly but not why I might want to use this property or why most are aliased as "global".

MSDN reference

Answer

Jon Skeet picture Jon Skeet · Nov 13, 2008

This is for "extern aliases". Suppose you want to use two different types, both of which are called Foo.Bar (i.e. Bar in a namespace of Foo). The two types will be in different assemblies (by definition) - you use the property in VS to associate an alias with each reference, then you can do:

extern alias FirstAlias;
extern alias SecondAlias;

using FirstBar = FirstAlias::Foo.Bar;
using SecondBar = SecondAlias::Foo.Bar;

and then use FirstBar and SecondBar in your code.

So basically it's an extra level of naming - and you shouldn't use it unless you really, really have to. It will confuse a lot of people. Try to avoid getting into that situation in the first place - but be aware of this solution for those times where you just can't avoid it.

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