Professional Visual Basic 2012 and .NET 4.5 Programming

Dynamic Loading of Assemblies

The preceding discussion about locating and loading assemblies refers to assemblies that are known at compile time through the application's references. There is an alternative method of locating and loading an assembly that is useful for certain scenarios.

In this technique, the location of the assembly is supplied by the application, using a URL or filename. The normal rules for locating the assembly do not apply — only the location specified by the application is used.

The location is just a string variable, so it may come from a configuration file or a database. In fact, the assembly to be loaded may be newly created, and perhaps did not even exist when the original application was compiled. Because the information to load the assembly can be passed into the application on the fly at run time, this type of assembly loading is called dynamic loading.

The LoadFrom Method of the Assembly Class

The Assembly class has a shared method called LoadFrom that takes a URL or filename and returns a reference to the assembly at that location. Here's a code example of LoadFrom in action, getting an assembly reference from a URL:

Dim asmDynamic As [Assembly]
asmDynamic = [Assembly].LoadFrom("http://www.dotnetmasters.com/DynamicWindows.dll")

As previously discussed, the brackets around Assembly are needed because it is a reserved keyword in Visual Basic. The brackets indicate that the word applies to the Assembly class, and the keyword is not being used.

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