CODEWITHSUNDEEP
c#asp.net
Control Freak
Control Freak

Reputation: 13233

Getting dynamic property value via string

I have a dynamic object that is generated from WebMatrix.Data:

dynamic obj;  [WebMatrix.Data.DynamicRecord]

So doing something like this is fine:

int ID = obj.ID;

However, trying to access the property by string like this:

obj.GetType().GetProperty("ID").GetValue(obj, null);

and I gets the following error: Cannot perform runtime binding on a null reference

I am assuming the WebMatrix.Data.DynamicRecord type is not used the same as the dynamic type? But it is declared as dynamic.

The following does return a type of WebMatrix.Data.DynamicRecord w/ a whole array of values:

obj.GetType();

However, the following returns a type of dynamic with value of null:

obj.GetType().GetProperty("ID");

I'm guessing that's why the error, but why is it null when obj.ID does not return null?

How do I get the property by string?

Upvotes: 0

Views: 498

Answers (1)

Jon Skeet
Jon Skeet

Reputation: 1500665

I'm guessing that's why the error, but why is it null when obj.ID does not return null?

GetProperty() will look for a CLR property on the type. That's not always how a dynamic property access works - DynamicRecord derives from DynamicObject, and I suspect it overrides the TryGetMember method which is used for property access (amongst other things). So basically, this is a property which is only available dynamically.

If you know that obj will always be a DynamicObject, you could always cast to that and call TryGetMember yourself... although you'd have to create your own GetMemberBinder. That's slightly awkward, but it looks like the only abstract member is FallbackGetMember, so you'd just need to work out how to implement that.

Upvotes: 1

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