如果 Unity C# 中的语句为 false，但 Watch 中的语句为 true

Question

I am currently developing an user interface editor for Unity3D. At this point I have a dictionary, with a key and value both representing a type. Based on the key type I want to add a component of the value type to a gameObject and return it:

protected Dictionary<string, string> eventHandlers = new Dictionary<string, string>();

public virtual EventHandler GetHandler(System.Type type)
{
    string name = type.Name;
    if(eventHandlers.ContainsKey(name))
    {
        System.Type eventHandlerType = TypeUtility.GetType(eventHandlers[name], null);
        return this.gameObject.AddComponent(eventHandlerType) as EventHandler;
    }
    return null;
}

The problem lies with my if statement. Appearantly, eventHandlers.ContainsKey(name) returns false, because the return null statement is called. However, the dictionary does contain the key. Even weirder: if I enter this statement into my watches in Visual Studio, it is true.

• I started out with a Dictionary but that wouldn't work out either.
• I looked into type, and it gave an exception for type.DeclaringMethod: System.InvalidOperationException: DeclaringMethod can only be used on generic arguments. However, I can access name fine, as you can see in the code above. String name is the right value and it doesn't break here.

Does anybody know why my if statement is false, when it is true in the watch? Can anybody point me in the right direction?

[edit] The values are:

name    "IOnClick"  System.String

eventHandlers   
    Count=1 
    System.Collections.Generic.Dictionary`2
        [
            [System.String, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089],
            [System.String, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]
        ]
    ["IOnClick"]    "OnClickHandler"    System.Collections.DictionaryEntry

type    "InterfaceEditor.EventSlots.IOnClick"   System.Type
    DeclaringMethod System.InvalidOperationException: DeclaringMethod can only be used on generic arguments System.Reflection.MethodBase
    Name    "IOnClick"  System.String

[edit2] So, I figured out where my problem lies.

The code above resides in my class InterfaceElement:

public abstract class InterfaceElement : MonoBehaviour, ISerializationCallbackReceiver
{
    protected Dictionary<string, string> eventHandlers = new Dictionary<string, string>();
}

For my different InterfaceElements, like my button, I figured I could just override the dictionary like this:

public class Button : InterfaceElement, IOnClick
{
    protected new Dictionary<string, string> eventHandlers = new Dictionary<string, string>()
    {
        { typeof(IOnClick).Name, typeof(OnClickHandler).Name }
    };
}

Appearantly, C# or Unity doesn't like this. What's the correct way to do something simular? I can't use the constructor, cause my InterfaceElement is a MonoBehaviour, right?

Answer 1

So. It turns out new does not do what I thought it would. New does not override a field, but rather hides the base field. This means the base class will still see the base field. My solution is to not use a field, but a method to return the dictionary, like this:

public abstract class InterfaceElement : MonoBehaviour
{
    protected virtual Dictionary<System.Type, System.Type> GetEventHandlers()
    {
        return null;
    }

    public virtual EventHandler GetHandler(System.Type type)
    {
        Dictionary<System.Type, System.Type> eventHandlers = GetEventHandlers();
        if(eventHandlers != null && eventHandlers.ContainsKey(type))
            return this.gameObject.AddComponent(eventHandlers[type]) as EventHandler;
        return null;
    }
}

public class Button : InterfaceElement, IOnClick
{
    protected override Dictionary<System.Type, System.Type> GetEventHandlers()
    {
        return new Dictionary<System.Type, System.Type>()
        {
            {typeof(IOnClick), typeof(OnClickHandler)}
        };
    }
}

Thank you for commenting and helping to find an answer!