ASP.NET Web API : How Can I Return Object of System.Type

Question

I have an assembly which is created using ASP.Net Framework Class Library Project. This assembly has lot of Types. Each Types has its own Methods, Fields and Properties.

Now I have written an ASP.Net Web API in which I am loading this assembly using var asmbly = Assembly.LoadFrom("assembly path"). Now in my API can I return an instance of Type from the loaded assembly? I am able to get the types using asmbly.GetTypes.

In my client WinForms application I am consuming this API and I want to get the instance of Type and show its Methods, Fields and Properties. Is it possible, am I doing it in right way?

In my Client application I am parsing through the type to get its methods, fields and properties using

private void loadObjectDetail(Object typeInstance)
{
MethodInfo[] actionMethods = typeInstance.GetMethods(BindingFlags.Instance | BindingFlags.Public);
FieldInfo[] fields = typeInstance.DeclaredFields;

/** Loading the contents to WinForms TreeView **/
}

Answer 1

You cannot return an instance of Type. In order for this to work you'd have to create an instance of Type which you cannot, at least the version that is being used. Type is abstract and the runtime creates a derived instance for types at runtime.

Even if you could do that it wouldn't make sense as the bulk of a Type is just metadata associated with the type that is running on the server. None of this is useful on the client side as all the client gets is the data and it can define its own structure (pulling in only what it wants). The method/constructor/etc members in the metadata and none of that would make it back to the client anyway.

It is important to remember that the big benefit of an API is separation of client/server behavior. The server has all the implementation details and the client just gets the raw data. Any functionality should be handled on the server side otherwise you are spreading functionality across the client and server which defeats the purpose of using APIs.

I'm not really sure why you would ever want to return a type from an API as types are just collections of data and functionality. It almost sounds like you might be using an API when you should really just be using a class library. But assuming you need to do this then you should normalize the Type to just the data the client needs. For example maybe you need the unique name so return the fully qualified type name. If you want to know what properties are available then expose the property metadata that defines the property name, type and whether it is read only or not. Same thing for methods.

public class TypeInformation
{
   public string Name { get; set; }
   public IEnumerable<PropertyInformation> Properties { get; set; }
}
public class PropertyInformation
{
   public string Name { get; set; }
   public string TypeName { get; set; }
   public bool IsReadOnly { get; set; }
}

But ultimately none of this is going to be directly usable on the client side. It isn't like they will be able to create a Type to represent any of that. Your best bet would be to just move the types into a class library and share it on both sides. In that case you just need to expose the actual type instance in the API.

//Sitting in a class library shared by client and server
public class SharedData
{
   //Some random data
   public string Id { get; set; }
   public string Name {  get; set; }
}

//API
ActionResult<SharedData> GetData ( int id )
{
   SharedData data = ...;

   return data;   
}

//Client
var data = httpClient.GetJsonAsync<SharedData>(10);

Answer 2

By definition, Web API returns only the pubic properties of an object. The client making the request must also have a reference to the type in order to instantiate the type on the client.

Answer 3

webapi does not return types. it returns data that may be serialized/deserialized to type and is language independant.

You might be interest in swagger-ui. It’s supplies an api that exposes the metadata of webapi requests and responses. This can be used to define classes for serialization and deserialization.

https://swagger.io/tools/swagger-ui/

Answer 4

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