views:

111

answers:

2

Question

I am trying to dynamically get the default for a type that is specified in a ParameterInfo. _methods[methodName] returns a MethodInfo object.

Unfortunately, the compiler doesn't like the "paramType" bit inside the default(paramType). I'm stumped.

Error

The type or namespace name 'paramType' could not be found (are you missing a using directive or an assembly reference?)

C:\Applications\...\MessageReceiver.cs Line 113

Example

object blankObject = null;
foreach (var paramInfo in _methods[methodName].Key.GetParameters())
{
    if (paramInfo.Name == paramName)
    {
        Type paramType = paramInfo.ParameterType;
        blankObject = (object)default(paramType);
    }
}
parameters[i] = blankObject;
A: 

I think default only works with the an actual type. It's a complier shortcut not an actual method. It works well with generics. for example:

public void MyMethod<T>(T obj)
{
   T myvar = default(T);
}

Check out this question I posted a while back:

Default Value for Generics

Micah
Right... I've used it with generics a lot, but now I need to get it from a ParameterInfo. Surely there is a way to do this through reflection or something.
Chris Benard
+6  A: 

It's quite simple to implement:

public object GetDefault(Type type)
{
    return type.IsValueType ? Activator.CreateInstance(type) : null;
}
Jon Skeet
Thanks man. It's great to have a celebrity answer my question. :) Repped.
Chris Benard
Don't get too starstruck. He answers _everyone's_ questions! :)
Michael Meadows