Question

I have a class which has the following constructor

public DelayCompositeDesigner(DelayComposite CompositeObject) {     InitializeComponent();      compositeObject = CompositeObject;   } 

along with a default constructor with no parameters.

Next I’m trying to create an instance, but it only works without parameters:

var designer = Activator.CreateInstance(designerAttribute.Designer); 

This works just fine, but if I want to pass parameters it does not:

var designer = Activator.CreateInstance(designerAttribute.Designer, new DelayComposite(4)); 

This results in an MissingMethodException:

Constructor voor type Vialis.LightLink.Controller.Scenarios.Composites.DelayCompositeDesigner was not found

Any ideas here?

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The problem is I really need to pass an object during construction.

You see I have a designer which loads all the types that inherit from the CompositeBase. These are then added to a list from which the users can drag them to a designer. Upon doing so an instance of the dragged is added to the designer. Each of these classes have custom properties defined on them:

[CompositeMetaData('Delay','Sets the delay between commands',1)] [CompositeDesigner(typeof(DelayCompositeDesigner))] public class DelayComposite : CompositeBase { } 

When the user selects an item in the designer, it looks at these attributes in order to load up a designer for that type. For example, in the case of the DelayComposite it would load up a user control which has a label and a slider which allow the user to set the ‘Delay’ property of the DelayComposite instance.

So far this works fine if I don’t pass any parameters to the constructor. The designer creates an instance of the DelayCompositeDesigner and assigns it to the content property of a WPF ContentPresenter.

But since that designer needs to modify the properties of the selected DelayComposite in the designer, I have to pass this instance to it. That is why the constructor looks lie this:

public DelayCompositeDesigner(DelayComposite CompositeObject) {     InitializeComponent();      compositeObject = CompositeObject; } 

Suggestions are welcome

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@VolkerK

The result of your code is this:

<—- foo Vialis.LightLink.Controller.Scenarios.Composites.DelayCompositeDesignerVoid .ctor() Vialis.LightLink.Controller.Scenarios.Composites.DelayCompositeDesignerVoid .ctor(Vialis.LightLink.Controller.Scenarios.Composites.DelayComposite) param:Vialis.LightLink.Controller.Scenarios.Composites.DelayComposite foo —->

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Leppie, you were correct, I had for some reason referenced the Composites assembly in my UI application… which is not something I should have done as I was loading it at runtime. The following code works:

object composite = Activator.CreateInstance(item.CompositType,(byte)205);                     var designer = Activator.CreateInstance(designerAttribute.Designer, composite); 

As you can see the code does not have knowledge of the DelayComposite type.

This solves the current problem, but introduces many new ones for what I want to achieve, either way thank you and thank you to everyone who has replied here.

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As for the following code, suggested by multiple people:

var designer = Activator.CreateInstance(     designerAttribute.Designer,      new object[] { new DelayComposite(4) }  ); 

The Activator.CreateInstance has a signature that looks like this:

Activator.CreateInstance(Type type, params object[] obj) 

So it should accept my code, but I will try the suggested code

UPDATE:

I’ve tried this as suggested:

var designer = Activator.CreateInstance(designerAttribute.Designer, new object[] { new DelayComposite(4)}); 

The result is the same.

Answer 1

I think you are dealing with a Type mismatch.

Likely the assembly is referenced in different places, or they are compiled against different versions.

I suggest you iterate through the ConstructorInfo’s and do a paramtype == typeof(DelayComposite) on the appropriate parameter.