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The alias keyword is used to indicate an external alias.

When you need to use several versions of the same assembly or assemblies with the same full qualified typenames, you need to use the alias and extern keywords to give different alias names for each version.

Example:

extern alias AppTools;
extern alias AppToolsV2;

To use the typenames of each version, you have the operator :: .

Example:

AppTools::MainTool tool_v1 = new AppTools::MainTool();
AppToolsV2::MainTool tool_v2 = new AppToolsV2::MainTool();

However, this only says to the compiler that there are several assemblies with typename conflicts. To relate what of each assemblies match's the alias name, you have to tell the compiler on its options apart the source. On dotNet command line, this options would be:

/r:AppTools=AppToolsv100.dll /r:AppToolsV2=AppToolsv200.dll

Notice: In order for it to be of use, you need to provide an external assembly to the compiler (e.g. pass /r:EXTALIAS=XXX.dll) and identify the external alias within the code (e.g. extern alias EXTALIAS;)



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