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Dynamically getting default of a parameter type

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;
like image 825
Chris Benard Avatar asked Jan 23 '09 22:01

Chris Benard


2 Answers

It's quite simple to implement:

public object GetDefault(Type type)
{
    return type.IsValueType ? Activator.CreateInstance(type) : null;
}
like image 200
Jon Skeet Avatar answered Nov 15 '22 02:11

Jon Skeet


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

like image 1
Micah Avatar answered Nov 15 '22 03:11

Micah