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
– George Mauer, Commented Jan 18, 2015 at 19:35
@GeorgeMauer they won't always be those types. I went ahead and updated the post. Thanks. — Justin Adkins
– Justin Adkins, Commented Jan 18, 2015 at 19:39

Justin Adkins · Accepted Answer · 2015-01-18 20:08:04Z

4

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

answered Jan 18, 2015 at 20:08

Justin Adkins

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Comments

Sergey Kalinichenko · Accepted Answer · 2015-01-18 19:27:16Z

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.

I'm not able to override VisitMethodCall. It's protected. The only thin you're able to override is Visit.
You can override protected methods in inheritor class. .Net allows to do such things
@JustinAdkins It shouldn't be an issue - take a look at this Q&A for an example.

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