cannot use dynamic type with asp.net vnext core

Question

I need to read and save a JSON file inside an ASP.NETt vNext app, and I would like to use a dynamic variable to store the value loaded using JSON.net, but when I go to compile I received this error message:

ASP.NET Core 5.0 error CS1980: Cannot define a class or member that utilizes 'dynamic' because the compiler required type 'System.Runtime.CompilerServices.DynamicAttribute' cannot be found. Are you missing a reference?

How can solve this? If I use dynamic, can I run an application using ASP.NET core?

Answer 1

You need to include the packages Microsoft.CSharp and System.Dynamic.Runtime for the aspnetcore50 framework.

This seems to work for me with CoreCLR version 1.0.0-beta1:

using Newtonsoft.Json.Linq;
using System;

namespace DynamicTest
{
    public class Program
    {
        public void Main(string[] args)
        {

            dynamic dobject = JObject.Parse("{number:1000, str:'string', array: [1,2,3,4,5,6]}");

            Console.WriteLine(dobject.number);
            Console.WriteLine(dobject.str);
            Console.WriteLine(dobject.array.Count);
            Console.ReadLine();
        }
    }
}

The project.json

{
    "version": "1.0.0-*",
    "dependencies": {
        "Newtonsoft.Json" :  "6.0.7"
    },
    "commands": { 
        "run" : "run"
    },
    "frameworks" : {
        "aspnet50" : { },
        "aspnetcore50" : { 
            "dependencies": {
                "System.Console": "4.0.0-beta-22231",
                "System.Dynamic.Runtime": "4.0.0-beta-22231",
                "Microsoft.CSharp": "4.0.0-beta-22231"
            }
        }
    }
}

Answer 2

I was fighting this problem, along with an even less useful error message...

The type or namespace name 'Linq' does not exist in the namespace 'System.Data'

But, I was running into the problem on my IIS Server (2012 R2 - IIS 8). Most of the posts I read on these problems were dealing with their development environment, not their web server.

In order to resolve both problems, I had to copy the System.Core.dll, from the servers framework folder (%windows path%\Microsoft.Net\Framework\v4.0.30319), into my web applications bin folder.

I'm not clear on why this was necessary, but I spent 3 days reading through documentation and forum posts, and nothing out there worked. We just got lucky...

Maybe this will help someone else that is struggling.