C# RLNET/OPENTK System.MissingMethodException during run-time

Question

I am trying to make a small 2d game in c# using the RLNET library. The RLNET library has OpenTK as a dependency, so I added the latest versions of both RLNET and OpenTK to my project using the NuGet packages manager in Visual Studio. I was following along with a tutorial explaining how to work with these libraries. But, when I got to running the code I ran into a MissingMethodException at run-time.

The tutorial I was following along with is here: https://roguesharp.wordpress.com/2016/03/02/roguesharp-v3-tutorial-creating-the-project/

The Solution Explorer shows both libraries included in the project under the References dropdown. And I also included them in my code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using RLNET;
using OpenTK;

namespace Rouge_Game
{
    class Program
    {
        private static readonly int _screenWidth = 100;
        private static readonly int _screenHeight = 70;

        private static RLRootConsole _rootConsole;

        static void Main(string[] args)
        {
            // This must be the exact name of the bitmap font file we are using or it will error.
            string fontFileName = "terminal8x8.png";
            // The title will appear at the top of the console window
            string consoleTitle = "RougeSharp V3 Tutorial - Level 1";
            // Tell RLNet to use the bitmap font that we specified and that each tile is 8 x 8 pixels
            _rootConsole = new RLRootConsole(fontFileName, _screenWidth, _screenHeight,
          8, 8, 1f, consoleTitle);
            // Set up a handler for RLNET's Update event
            _rootConsole.Update += OnRootConsoleUpdate;
            // Set up a handler for RLNET's Render event
            _rootConsole.Render += OnRootConsoleRender;
            // Begin RLNET's game loop
            _rootConsole.Run();
        }

        // Event handler for RLNET's Update event
        private static void OnRootConsoleUpdate(object sender, UpdateEventArgs e)
        {
            _rootConsole.Print(10, 10, "It worked!", RLColor.White);
        }

        // Event handler for RLNET's Render event
        private static void OnRootConsoleRender(object sender, UpdateEventArgs e)
        {
            // Tell RLNET to draw the console that we set
            _rootConsole.Draw();
        }
    }
}

The part of the code that has a run time error is this:

    // Event handler for RLNET's Render event
        private static void OnRootConsoleRender(object sender, UpdateEventArgs e)
        {
            // Tell RLNET to draw the console that we set
            _rootConsole.Draw();
        }

When I run the project it compiles with no errors and the program launches, but then throws this exception:

System.MissingMethodException
  HResult=0x80131513
  Message=Method not found: 'Void 
OpenTK.Graphics.OpenGL.GL.BlendFunc(OpenTK.Graphics.OpenGL.BlendingFactorSrc, OpenTK.Graphics.OpenGL.BlendingFactorDest)'.
  Source=RLNET
  StackTrace:
   at RLNET.RLRootConsole.Draw()
   at Rouge_Game.Program.OnRootConsoleRender(Object sender, UpdateEventArgs e) in C:\Users\pjmul\source\repos\Rouge Game\Rouge Game\Program.cs:line 45
   at RLNET.RLRootConsole.window_RenderFrame(Object sender, FrameEventArgs e)
   at System.EventHandler`1.Invoke(Object sender, TEventArgs e)
   at OpenTK.GameWindow.OnRenderFrame(FrameEventArgs e)
   at OpenTK.GameWindow.RaiseRenderFrame(Double elapsed, Double& timestamp)
   at OpenTK.GameWindow.DispatchRenderFrame()
   at OpenTK.GameWindow.Run(Double updates_per_second, Double frames_per_second)
   at OpenTK.GameWindow.Run(Double updateRate)
   at RLNET.RLRootConsole.Run(Double fps)
   at Rouge_Game.Program.Main(String[] args) in 
C:\Users\pjmul\source\repos\Rouge Game\Rouge Game\Program.cs:line 32

I don't understand this error however as when I use the object viewer built into Visual Studio I can find the "missing" function when I open OpenTK.dll. Any suggestions as to how I might fix this error are greatly appreciated. I would also like to thank anyone who takes the time to help me in advance.

Answer 1

There is something wrong with the 3.x branch of OpenTK. Try downgrading your OpenTK package back to 2.x and it will work.