Get MethodInfo from Expression tree

Question

I have the following method:

public TResult Call<TResult>(Expression<Func<T, TResult>> code)
{
    var returnValue = default(TResult);
    // code that will inspect the interface method that is being called 
    // along with lots of other code
    // and then call a WebAPI service.
    return returnValue;
}

In this instance, T is an interface named ICustomer and TResult will be a class CustomerData In this specific instance, I'm doing the following:

var model = client.Call(customer => customer.Get(1));

My ultimate goal with this is to be able to inspect the interface method for certain attributes. Based on those attributes, I'd like to call a WebAPI service and pass to it any parameters that were in the interface method.

How do I figure out in the Call method that the interface.Get(1) method was called?

You should put some type constraints on T and TResult if they're always going to be those types. — George Mauer, Jan 18 '15 at 19:35
@GeorgeMauer they won't always be those types. I went ahead and updated the post. Thanks. — Justin Adkins, Jan 18 '15 at 19:39

score 4 · Answer 1 · answered Jan 18 '15 at 20:08

4

After fooling around, All I needed to do was cast the Body of the expression as MethodCallExpression.

answered Jan 18 '15 at 20:08

Justin Adkins

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score 2 · Answer 2 · answered Jan 18 '15 at 19:27

2

You can try using ExpressionVisitor for this. Overriding VisitMethodCall method will let you examine each method call inside the expression. In case of customer => customer.Get(1) you would get a single callback with MethodCallExpression with Object property set to ParameterExpression representing customer, Method parameter set to MethodInfo of the Get method, and Arguments set to a collection of a single constant expression representing integer constant 1.

answered Jan 18 '15 at 19:27

Sergey Kalinichenko

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I'm not able to override `VisitMethodCall`. It's protected. The only thin you're able to override is `Visit`. – Justin Adkins Jan 18 '15 at 19:51
1

You can override protected methods in inheritor class. .Net allows to do such things – Sergey Litvinov Jan 18 '15 at 23:51
@JustinAdkins It shouldn't be an issue - take a look at [this Q&A](http://stackoverflow.com/q/11164009/335858) for an example. – Sergey Kalinichenko Jan 19 '15 at 00:48

Get MethodInfo from Expression tree

2 Answers2