Dynamic invoke of a method using named parameters

Question

We're currently using .NET 3.5 and part of our application uses dynamic invocation (using MethodBase.Invoke)

I am wondering if it is possible to mix in Named Parameters (in .NET 4) with dynamic invocation, to perform something similar to:

// Dictionary that holds parameter name --> object mapping
var parameters = new Dictionary<string, object>();

// Add parameters ....

// Invoke where each parameter will match the one from the method signature.
methodInfo.Invoke(obj, parameters);

Is there any API that allows this option out of the box? If not, is it possible to develop some solution to perform this?

EDIT:

Rethinking of this problem, it sounds similar to how the compiler may actually need to match method calls based on argument lists. Perhaps there's some Compiler API (or the new Roslyn project) that allows doing just this easily? (without coding it myself which may be prone to errors).

Jordão · Accepted Answer · 2019-10-17 11:07:13Z

22

You can use code like this:

public static class ReflectionExtensions {

    public static object InvokeWithNamedParameters(this MethodBase self, object obj, IDictionary<string, object> namedParameters) { 
        return self.Invoke(obj, MapParameters(self, namedParameters));
    }

    public static object[] MapParameters(MethodBase method, IDictionary<string, object> namedParameters)
    {
        string[] paramNames = method.GetParameters().Select(p => p.Name).ToArray();
        object[] parameters = new object[paramNames.Length];
        for (int i = 0; i < parameters.Length; ++i) 
        {
            parameters[i] = Type.Missing;
        }
        foreach (var item in namedParameters)
        {
            var paramName = item.Key;
            var paramIndex = Array.IndexOf(paramNames, paramName);
            if (paramIndex >= 0)
            {
                parameters[paramIndex] = item.Value;
            }
        }
        return parameters;
    }
}

And then call it like this:

var parameters = new Dictionary<string, object>();
// Add parameters ...
methodInfo.InvokeWithNamedParameters(obj, parameters);

edited Oct 17, 2019 at 11:07

answered Oct 25, 2012 at 16:02

Jordão

56.8k13 gold badges118 silver badges147 bronze badges

Sign up to request clarification or add additional context in comments.

8 Comments

lysergic-acid Over a year ago

What would happen if the method uses default parameter values (.NET 4 feature)? does this solution work in that case? (can it differentiate between a null passed parameter, to a parameter that should not be passed (and thus take the default value)? I am not sure, but i will take the code and test that!

Jordão Over a year ago

@lysergic-acid: look here for some ideas.

lysergic-acid Over a year ago

awesome so basically i can amend your example to reflect for these attributes and get the default value into the array in any case. Thanks!

Jordão Over a year ago

I've changed the code to initialize the parameters with Type.Missing to account for optional parameters. But I haven't tested it, please check that it works.

Fred Over a year ago

You might want to check if paramIndex != -1 before you set the value to prevent IndexOutOfRangeException.

|

Community · Accepted Answer · 2017-05-23 10:30:04Z

1

you can get your paramter names with the help of this article How can you get the names of method parameters? and then you can reorder them to invoke them as described here Reflection: How to Invoke Method with parameters

edited May 23, 2017 at 10:30

CommunityBot

11 silver badge

answered Oct 25, 2012 at 15:31

TGlatzer

6,4252 gold badges30 silver badges49 bronze badges

Comments

jbtule · Accepted Answer · 2012-10-29 20:06:31Z

1

With .net4, I have an opensource framework ImpromptuInterface (found in nuget) that makes it easy to use the DLR apis for late invocation including named/optional parameters.

var result = Impromptu.InvokeMember(target, "MyMethod", parameters.Select(pair=>  InvokeArg.Create(pair.Key, pair.Value)).Cast<object>().ToArray());

answered Oct 29, 2012 at 20:06

jbtule

31.9k12 gold badges101 silver badges129 bronze badges

Collectives™ on Stack Overflow

Dynamic invoke of a method using named parameters

3 Answers 3

8 Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

8 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related