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Support for dynamic object parameter/variable (ExpandoObject) #16
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👍 Any news on this? |
No, sorry. For now I don't have any news. I have tried to post a question on stackoverflow but without success: I have found a way to solve this only using unsupported/private methods. And I really don't like it. |
Have you tried deriving from the public (abstract) class DynamicMetaObjectBinder in the Also, I have done some research. Consider the following test program: using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
namespace TestProject
{
public class Program
{
public static void Test()
{
dynamic test = "Hello";
object result = test.Length;
Console.WriteLine(result);
}
}
} When decompiled using ILSpy, what you get is this: using Microsoft.CSharp.RuntimeBinder;
using System;
using System.Linq.Expressions;
using System.Runtime.CompilerServices;
namespace TestProject
{
public class Program
{
[CompilerGenerated]
private static class <Test>o__SiteContainer0
{
public static CallSite<Func<CallSite, object, object>> <>p__Site1;
}
public static void Test()
{
object test = "Hello";
if (Program.<Test>o__SiteContainer0.<>p__Site1 == null)
{
Program.<Test>o__SiteContainer0.<>p__Site1 = CallSite<Func<CallSite, object, object>>.Create(Binder.GetMember(CSharpBinderFlags.None, "Length", typeof(Program), new CSharpArgumentInfo[]
{
CSharpArgumentInfo.Create(CSharpArgumentInfoFlags.None, null)
}));
}
object result = Program.<Test>o__SiteContainer0.<>p__Site1.Target(Program.<Test>o__SiteContainer0.<>p__Site1, test);
Console.WriteLine(result);
}
}
} Which appears to reveal the inner workings of the dynamic keyword. I've manually edited this to make it more readable and remove insignificant parts: public class Program
{
[CompilerGenerated]
private static class Container
{
public static CallSite<Func<CallSite, object, object>> Site;
}
public static void Test()
{
object test = "Hello";
if (Program.Container.Site == null)
{
Program.Container.Site = CallSite<Func<CallSite, object, object>>.Create(
Binder.GetMember(
CSharpBinderFlags.None,
"Length",
typeof(Program),
new CSharpArgumentInfo[]
{
CSharpArgumentInfo.Create(CSharpArgumentInfoFlags.None, null)
}));
}
object result = Program.Container.Site.Target(Program.Container.Site, test);
Console.WriteLine(result);
}
} Now I'm assuming that we're dealing with two things here:
I would think that the CallSite stuff is related to the caching mechanism, so let's strip that away: public static void Test()
{
object test = "Hello";
var callSite = CallSite<Func<CallSite, object, object>>.Create(
Binder.GetMember(
CSharpBinderFlags.None,
"Length",
typeof(Program),
new CSharpArgumentInfo[]
{
CSharpArgumentInfo.Create(CSharpArgumentInfoFlags.None, null)
}));
object result = callSite.Target(callSite, test);
Console.WriteLine(result);
} Digging into the CallSite code reveals that the Create method actually requires a CallSiteBinder, just like the one required by
However, what it does (thanks ILSpy again :D ) appears to be nothing more than creating a |
My similar project CSharpEval supports dynamics. I also used ILSpy to get a gist of what the compiler was doing. It probably isn't perfect, but it works. You just put the binder you created in an Expression.Dynamic. Property Getter: var binder = Binder.GetMember(
CSharpBinderFlags.None,
membername,
type,
new[] { CSharpArgumentInfo.Create(CSharpArgumentInfoFlags.None, null) }
);
Expression result = Expression.Dynamic(binder, typeof(object), instance); Property Setter (upon checking that the left hand expression is a dynamic): var dle = (DynamicExpression)le;
var membername = ((GetMemberBinder)dle.Binder).Name;
var instance = dle.Arguments[0];
var binder = Binder.SetMember(
CSharpBinderFlags.None,
membername,
type,
new[]
{
CSharpArgumentInfo.Create(CSharpArgumentInfoFlags.None, null),
CSharpArgumentInfo.Create(CSharpArgumentInfoFlags.None, null)
}
);
return Expression.Dynamic(binder, typeof(object), instance, re); Method Call: var binderM = Binder.InvokeMember(
CSharpBinderFlags.None,
membername,
null,
type,
expArgs.Select(x => CSharpArgumentInfo.Create(CSharpArgumentInfoFlags.None, null))
);
return Expression.Dynamic(binderM, typeof(object), expArgs); You also have to catch unary and binary expressions and handle dynamics accordingly: Binary: var expArgs = new List<Expression>() { le, re };
var binderM = Binder.BinaryOperation(CSharpBinderFlags.None, expressionType, le.Type,
new CSharpArgumentInfo[]
{
CSharpArgumentInfo.Create(CSharpArgumentInfoFlags.None, null),
CSharpArgumentInfo.Create(CSharpArgumentInfoFlags.None, null)
});
return Expression.Dynamic(binderM, typeof(object), expArgs); All this is in the AntlrParser branch, ExpressionEvaluator project, ExpressionHelper.cs. My code is terrible, btw, but hopefully you can get some information from it. |
Thank you Adam and Rupert for your comments! I really appreciate it. I usually don't like to use code marked as
So my idea is to support some kind of extension mechanism used to plugin special/custom implementations. I will try to work on this on the first occasion! P.S. Just don't understand why Microsoft doesn't write a better documentation and official support for dynamic 👎 ! |
Have you tried something lik this: http://stackoverflow.com/questions/3562088/c-sharp-4-dynamic-in-expression-trees ? Expression GenerateAdd(Expression left, Expression right)
{
if (left.Type == typeof(string) && right.Type == typeof(string))
{
return GenerateStaticMethodCall("Concat", left, right);
}
if (left.Type == typeof (object) || right.Type == typeof (object))
return GenerateDynamicBinary(ExpressionType.Add, left, right);
return Expression.Add(left, right);
}
Expression GenerateDynamicBinary(ExpressionType exprType, Expression left, Expression right)
{
var binder = Microsoft.CSharp.RuntimeBinder.Binder.BinaryOperation(
CSharpBinderFlags.None, exprType, GetType(),
new[]
{
CSharpArgumentInfo.Create(CSharpArgumentInfoFlags.None, null),
CSharpArgumentInfo.Create(CSharpArgumentInfoFlags.None, null)
});
return Expression.Dynamic(binder, typeof(object), left, right);
} I'm not sure if it is right solution, but this test code works now: dynamic a = 5;
dynamic b = 6;
dynamic obj = new { a, b };
var target = new Interpreter();
target.SetVariable("obj", obj);
Assert.AreEqual(a + b, target.Eval("obj.a + obj.b")); |
Thanks @pgolinski for your code.
https://msdn.microsoft.com/en-us/library/microsoft.csharp.runtimebinder.binder%28v=vs.110%29.aspx Anyway probably it is the only easy solution...the any other solution that I think of is to create a custom Binder class. Can I ask you to send a pull request, so I can easily merge it. thanks! |
The code I pasted is all I have changed, so a pull request made from it would be quite useless. |
👍 I don't like it either, but this might your best bet. That or risk venturing into the uncharted waters of Roslyn circa VS2015 CTP. |
Thanks to all! I'm just releasing version 1.3.3 with partial dynamic support (get properties and method invocation). |
See also:
http://stackoverflow.com/questions/21982040/using-dynamic-types-with-espresso
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