Delphi project group, referencing a project

Delphi "Project group" is the concept similar to Visual Studio Solution.

If you use Delphi and not Delphi Prizm, it means you're not developing .NET assemblies but you're developing native Windows code. For native Windows, there is no a concept of assembly and there is no a concept of references.

Unfortunately, you can use only less robust lower-level concept of exporting and importing methods, which are not even object-oriented. (You can simulate very basic object-oriented features via explicit passing of "self" parameters, but this is an advanced technique which requires good understanding of OOP internals.) You can also use Delphi concept of package which is technically based on native import/export but ideologically close to .NET (Delphi is a major .NET predecessor). But packages are between Delphi projects. Let's talk about consuming native DLL in Delphi. Import is performed in source code using external key word.

Here is a simple example:

procedure DllMessage; external 'SimpleMessageDLL.dll';

Find a full code sample here:
http://delphi.about.com/od/windowsshellapi/a/dll_basics.htm[^].

Alternatively, you can load a DLL during run-time using Windows API LoadLibrary/LoadLibraryEx and access DLL methods using GetProcAddress. See:
http://msdn.microsoft.com/en-us/library/ms684175(v=vs.85).aspx[^],
http://msdn.microsoft.com/en-us/library/ms684179(v=vs.85).aspx[^],
http://msdn.microsoft.com/en-us/library/ms683212(v=vs.85).aspx[^].

—SA