How to get a Type from an object in another DLL?

Question

I've got an object called "Communication" that has a method to "CreatePdfFromTemplate". This method is going to be called from a Windows Service that has a SqlDependancy on a table that will notify when a new row is added by a method on a website.

Into my method, I pass a list of custom objects that have an "Id" and a "Name". The name, is the name of the object I need to load using reflection. For example, "Instruction". The "Id" is the Id of the object referred to in "Name" that needs to be loaded from the database. This object is not referenced or available in the runtime of my "Communication" DLL.

I'm currently falling at the first hurdle. I am trying to do the following as a first step:

// Load object information using Reflection
Type objectType = Assembly.GetExecutingAssembly().GetType(queueObject.Name);
int objectId = queueObject.Id;

I have found some info from my searches for answers that say there is a way to load a DLL by making it available in the application cache or the GAC, but I wasn't sure if this was the best way to go.

I've never used Reflection before so if you have any advice on it, or any advice on the way I have chosen to structure this in general (i.e. website adds row to DB table, SqlDependancy in Windows Service fires, calls to Communication service DLL to create PDF).

Just to give you some more information, the reason I have chosen to do it like this, is because my templates contain tags such as {Instruction.CreatedDate} where "Instruction" is the name of the object and "CreatedDate" is the name of a property, the value of which will replace the tag.

Any help on how to load this "Instruction" object in my Reflection or just on my structure in general is much appreciated. Let me know if I haven't given enough info or if what I've said isn't clear enough (this is my first StackOverflow question, although I am a long time lurker).

Thanks.

--UPDATE--

Ok, using the idea put forward from Maarten, I have managed to load my assembly and get a type from it, but I've done it slightly differently. I wasn't able to put in a specific path using the Assembly.LoadFile method, so I've done it like this:

Assembly executingAssembly = Assembly.GetExecutingAssembly();
Assembly objectAssembly = Assembly.Load(executingAssembly
                                          .GetReferencedAssemblies()
                                          .Where(a => a.Name == "Common")
                                          .FirstOrDefault());

This works because the Type I am trying to get, is part of a referenced assembly in my Communication service called "Common" (which is an installed package using nuget to help keep it up to date, as it changes quite often).

Any further posts on how I'm doing this and if it's the right or wrong way would be appreciated though!

Answer 1

Load the assembly using Assembly.LoadFile or another overload.

Get the type using Assembly.GetType.

Use the Activator.CreateInstance once you have the type.

Cast it to dynamic, and call your method, or set your property. I'm assuming you are using .net 4.0.

var myAssembly = Assembly.LoadFile(...);
var myType = myAssembly.GetType(...);
dynamic myObject = Activator.CreateInstance(myType);
if (myObject != null) {
    var createdDate = myObject.CreatedDate;
}