C# ‘dynamic’ cannot access properties from anonymous types declared in another assembly

Question

Code below is working well as long as I have class ClassSameAssembly in same assembly as class Program. But when I move class ClassSameAssembly to a separate assembly, a RuntimeBinderException (see below) is thrown. Is it possible to resolve it?

using System;

namespace ConsoleApplication2
{
    public static class ClassSameAssembly
    {
        public static dynamic GetValues()
        {
            return new
            {
                Name = "Michael", Age = 20
            };
        }
    }

    internal class Program
    {
        private static void Main(string[] args)
        {
            var d = ClassSameAssembly.GetValues();
            Console.WriteLine("{0} is {1} years old", d.Name, d.Age);
        }
    }
}

Microsoft.CSharp.RuntimeBinder.RuntimeBinderException: 'object' does not contain a definition for 'Name'

at CallSite.Target(Closure , CallSite , Object )
at System.Dynamic.UpdateDelegates.UpdateAndExecute1[T0,TRet](CallSite site, T0 arg0)
at ConsoleApplication2.Program.Main(String[] args) in C:\temp\Projects\ConsoleApplication2\ConsoleApplication2\Program.cs:line 23

Solution 1

I believe the problem is that the anonymous type is generated as internal, so the binder doesn't really "know" about it as such.

Try using ExpandoObject instead:

public static dynamic GetValues()
{
    dynamic expando = new ExpandoObject();
    expando.Name = "Michael";
    expando.Age = 20;
    return expando;
}

I know that's somewhat ugly, but it's the best I can think of at the moment... I don't think you can even use an object initializer with it, because while it's strongly typed as ExpandoObject the compiler won't know what to do with "Name" and "Age". You may be able to do this:

 dynamic expando = new ExpandoObject()
 {
     { "Name", "Michael" },
     { "Age", 20 }
 };
 return expando;

but that's not much better...

You could potentially write an extension method to convert an anonymous type to an expando with the same contents via reflection. Then you could write:

return new { Name = "Michael", Age = 20 }.ToExpando();

That's pretty horrible though :(

Solution 2

You could use [assembly: InternalsVisibleTo("YourAssemblyName")] to make you assembly internals visible.

Solution 3

I ran into a similair problem and would like to add to Jon Skeets answer that there is another option. The reason I found out was that I realized that many extension methods in Asp MVC3 uses anonymous classes as input to provide html attributes (new {alt="Image alt", style="padding-top: 5px"} =>

Anyway - those functions use the constructor of the RouteValueDictionary class. I tried that myself, and sure enough it works - though only the first level (I used a multi-level structure). SO - in code this would be:

object o = new {
    name = "theName",
    props = new {
        p1 = "prop1",
        p2 = "prop2"
    }
}
SeparateAssembly.TextFunc(o)

//In SeparateAssembly:
public void TextFunc(Object o) {
  var rvd = new RouteValueDictionary(o);

//Does not work:
Console.WriteLine(o.name);
Console.WriteLine(o.props.p1);

//DOES work!
Console.WriteLine(rvd["name"]);

//Does not work
Console.WriteLine(rvd["props"].p1);
Console.WriteLine(rvd["props"]["p1"]);

SO... What is really going on here? A peek inside the RouteValueDictionary reveals this code (values ~= o above):

foreach (PropertyDescriptor descriptor in TypeDescriptor.GetProperties(values))
    object obj2 = descriptor.GetValue(values);
    //"this.Add" would of course need to be adapted
    this.Add(descriptor.Name, obj2);
}

SO - using TypeDescriptor.GetProperties(o) we would be able to get the properties and values despite the anonymous type being constructed as internal in a separate assembly! And of course this would be quite easy to extend to make it recursive. And to make an extension method if you wanted.

Hope this helps!

/Victor

Solution 4

Here is a rudimentary version of an extension method for ToExpandoObject that I'm sure has room for polishing.

    public static ExpandoObject ToExpandoObject(this object value)
    {
        // Throw is a helper in my project, replace with your own check(s)
        Throw<ArgumentNullException>.If(value, Predicates.IsNull, "value");

        var obj = new ExpandoObject() as IDictionary<string, object>;

        foreach (var property in value.GetType().GetProperties(BindingFlags.Public | BindingFlags.Instance))
        {
            obj.Add(property.Name, property.GetValue(value, null));
        }

        return obj as ExpandoObject;
    }

    [TestCase(1, "str", 10.75, 9.000989, true)]
    public void ToExpandoObjectTests(int int1, string str1, decimal dec1, double dbl1, bool bl1)
    {
        DateTime now = DateTime.Now;

        dynamic value = new {Int = int1, String = str1, Decimal = dec1, Double = dbl1, Bool = bl1, Now = now}.ToExpandoObject();

        Assert.AreEqual(int1, value.Int);
        Assert.AreEqual(str1, value.String);
        Assert.AreEqual(dec1, value.Decimal);
        Assert.AreEqual(dbl1, value.Double);
        Assert.AreEqual(bl1, value.Bool);
        Assert.AreEqual(now, value.Now);
    }

Solution 5

A cleaner solution would be:

var d = ClassSameAssembly.GetValues().ToDynamic();

Which is now an ExpandoObject.

Remember to reference:

Microsoft.CSharp.dll

View more solutions

Comments

[Dave Markle]

Thanks Jon. I just had the same problem using a class which happened to be private to the assembly.

[ProfK]

I would love something like your horrible example at the end though, just not as horrible. To use: dynamic props = new {Metadata = DetailModelMetadata.Create, PageTitle = "New Content", PageHeading = "Content Management"}; and have the named props added as dynamic members would be great!

[Victor]

Sorry for that confusion. Code updated from prop1 => p1 where appropriate. Still - the idea with the entire post was to put forward TypeDescriptor.GetProperties as an option to solve the problem, which hopefully was clear anyway...

[jbtule]

The open source framework impromptu interface does a lot with the dlr it has an inline initialization syntax that works for any object dynamic or static. return Build<ExpandoObject>.NewObject(Name:"Micheal", Age: 20);

[Jimmy Bosse]

The problem with this solution is that the ExpandoObject will serialize as an array of key value pairs while the anonymous type will serialize s expected. Using the InternalsVisibleTo will remove the error, but this won't work if you expect your object to be consumed by unknown sources. In my case I needed to allow my unit tests to be able access the properties and I needed to serialize the object to JSON so the InternalsVisibleTo was a better solution for my use case.

[kelloti]

Jon's answer is more complete, but this actually provides a reasonably simple workaround for me. Thanks :)

[Kiquenet]

any full source code sample for an extension method to convert an anonymous type to an expando ?

[Jon Skeet]

@Kiquenet: Not that I know offhand, but it should be pretty simple just using Type.GetProperties and iterating over the results, fetching them and putting them into the Expando as a dictionary.

[Faisal Mq]

I was banging my head for hours on different forums but found no simple answer except this one. Thanks Luke. But still I cannot understand why a dynamic type is not accessible outside an assembly like it does in same assembly? I mean why is this restriction in .Net.

[Paťo Debute Krehák]

@FaisalMq it's because the compiler that generate the anonymous classes declares them "internal". Don't know which is the real reason.

[lbrahim]

@JonSkeet How do I write extension method for 'Anonymous Types'? Like public static dynamic ToExpando(this ? dynamicObject){//Do Sth} How do I tell it to get ToExpando on 'Anonymous Types' only?

[Jon Skeet]

@Md.lbrahim: You can't, basically. You'd have to do it either on object or on a generic type (you can require that it's a class...) and check the type at execution time.

[Igor Mironenko]

Yes, I think this answer is important, because I don't want to change working code, I just need to test it from another assembly

[trevorgk]

An annoying problem, I put the repetive logic into following method: private static dynamic Expando(string blurb, string imageSrc, string navUrl) { dynamic expando = new ExpandoObject(); expando.Blurb = blurb; expando.ImageSrc = imageSrc; expando.NavigateUrl = navUrl; return expando; }

[Rady]

One note to add here is that you need to restart Visual Studio after this change for this to work.