Question

Is it possible to load external “web-parts” in an ASP.NET website? I would like to make stand-alone dll’s containing a User-Control or Page to include in a main site. Like a plug-in architecture for websites.

The only examples I can seem to find bind the user control to the main project, you need to have a “hard” reference to the control.

What I would like is to define a shared interface which the plugins can implement, and the website can load and display.

Answer 1

There is a discussion over here about compiling UserControls into dlls

ASP.NET UserControl class library

For something like what you are describing, I would highly recommend creating custom server controls. You could provide an abstract base class for all plug ins.

public abstract class PluginBase : WebControl {

}

Then you could search a directory for assemblies and search each assembly for anything deriving from that type.

    DirectoryInfo di = new DirectoryInfo(path);
    FileInfo[] assemblies = di.GetFiles("*.dll");
    foreach (var assembly in assemblies) {
        Assembly a = Assembly.LoadFrom(assembly.FullName);
        foreach (Type type in a.GetTypes()) {
            if (type.BaseType == typeof(PluginBase)) {                     
                //load plugin
            }
        } 
    }

You can also register your plug ins in your web.config by providing a config section like the example here