DLL reference location

Question

Okay, I asked this question the other day, and it was closed due to my vagueness. I'll try to be more specific. In a project, say C# (using Visual Studio), I add a reference to a dll (right-click References->Add Reference), and the location of said dll is in C:\Blah\Foo. Now, if I move the exe that is built over to another machine, will the location of the dll need to be with the exe, or will it need to be in C:\Blah\Foo? Thank you.

Answer 1

When you add a reference in the way you've described it is copied to the output folder (same as the exe file). Look in the properties of the reference (F4) and you will see an option called "Copy Local", if this is set to true then the DLL will be copied to the same output folder as the EXE file.

So when you deploy your application to another machine you will need to copy the exe and all it's referenced DLLs to the deployment location. Windows will search for DLLs in a number of locations, the first of which is the same folder as the EXE file.

Answer 2

Typically, you'll just put the assemblies in the same folder as the application, which causes it to be in the default probing path, and get found (for most applications), but there are many other options depending on the type of application. When you define your reference, there is the option to "Copy Local" - which causes the assembly to be copied to the application's output folder. If you leave this set to True, the assembly (DLL) will be with the .exe, and typically "just work."

The full process the runtime uses is covered on MSDN in How the Runtime Locates Assemblies. In particular, the topic titled Locating the Assembly through Codebases or Probing covers how the assemblies are located in detail, which depends on a lot of factors.