Question

With the DLR, i would like to do something like this:

class MyClass {
   int MyProperty { get; set; }
}

In razor, I would do something like this. (InstanceOfMyClass is some dynamic object that looks at an instance of MyClass)

@InstanceOfMyClass.MyProperty

This would output the string representation of MyProperty.

Now if I do this.

@InstanceOfMyClass.MyMissingProperty

I would like it to output “Missing: MyMissingProperty”. I would love to capture the whole expression, like so.

@InstanceOfMyClass.MyMissingProperty.MoreMissing

Could potentially output “Missing: MyMissingProperty.MoreMissing”, but that might be asking a lot of the DLR.

Will the ExpandoObject allow me to do this? If not, what do I have to do to implement this?

Answer 1

Extend DynamicObject.TryGetMember in this way:

If the member exists, return the value. If the member doesn’t exist, return a new instance of a class that will handle both the string representation of the missing property and also the chain. Something like this

public class MissingPropertyChain : DynamicObject
{
    private string property;

    public MissingPropertyChain(string property)
    {
        this.property = property;
    }

    public override bool TryGetMember(GetMemberBinder binder, out object result) 
    {
        if(binder.Name == "ToString")
            result = "Missing property: " + property;
        else
            result = new MissingPropertyChain( property + "." + binder.Name;

        return true;
    }
}

I didn’t try it, but I think it will give you the idea of how to solve the problem.

Hope it helps.