How to reference a DLL on runtime?

Question

I\'m building an application with WPF and C#, basically I want to allow anyone to create a dll and put it into a folder (similar to plugins). The application will take all t

Answer 1

The answers above pretty much give you what you need. You can try to load all dlls to be plugged into your app when the program starts up:

// note: your path may differ, this one assumes plugins directory where exe is executed
var pluginsDirectory = Path.Combine(AppContext.BaseDirectory, "plugins");
if (Directory.Exists(pluginsDirectory))
{
    var dllPaths = Directory.GetFiles(pluginsDirectory);
    if (dllPaths.Count() > 0)
    {
        foreach (var dllPath in dllPaths)
        {
            Assembly.LoadFrom(Path.Combine("plugins", Path.GetFileName(dllPath)));
        }
    }
    else
    {
        // warn about no dlls
    }
}
else
{
    // warn about no plugins directory
}

How to reference the dll and its types:

// if dll file name is My.Plugin.Assembly.ShortName.dll, then reference as follows
var pluginAssembly = Assembly.Load("My.Plugin.Assembly.ShortName");
var typesInAssembly = pluginAssembly.GetExportedTypes();
var instanceType = typesInAssembly.FirstOrDefault(t => t.Name == "MyClassName");
var instance = Activator.CreateInstance(instanceType, new object[] { "constructorParam1", "constructorParam2" });
instanceType.InvokeMember("MyMethod", BindingFlags.InvokeMethod, null, instance, new object[] { "methodParam1", "methodParam2" });

You may need to tell your app configuration to probe your plugins directory. I'm assuming one child directory of plugins, you can probe a list of subdirectory paths.

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You will need something to tell you which type to implement (perhaps configuration mapping). The interface, as best I can tell, will just provide a contract all the plugins implement to provide an expected method to invoke via reflection.