✅ ImGui.NET and OpenTK

using System;
using ImGuiNET;
using OpenTK;
using OpenTK.Graphics;
using OpenTK.Graphics.OpenGL4;
using OpenTK.Mathematics;
using OpenTK.Windowing.Common;
using OpenTK.Windowing.Desktop;

namespace ImGuiWithOpenTK
{
    class Program
    {
        private static GameWindow gameWindow;

        public static void Main(string[] args)
        {
            NativeWindowSettings nativeWindowSettings = new NativeWindowSettings
            {
                Size = new Vector2i(800, 600),
                Title = "ImGui with OpenTK",
                API = ContextAPI.OpenGL,
                APIVersion = new Version(4, 6),
            };

            GameWindowSettings gameWindowSettings = new GameWindowSettings
            {
                UpdateFrequency = 60
            };

            gameWindow = new GameWindow(gameWindowSettings, nativeWindowSettings);

            gameWindow.Load += GameWindow_Load;

            gameWindow.RenderFrame += GameWindow_RenderFrame;

            gameWindow.UpdateFrame += GameWindow_UpdateFrame;

            gameWindow.Run();
        }

        private static void GameWindow_UpdateFrame(FrameEventArgs obj)
        {

        }

        private static void GameWindow_RenderFrame(FrameEventArgs obj)
        {
            GL.Clear(ClearBufferMask.ColorBufferBit | ClearBufferMask.DepthBufferBit);

            ImGui.NewFrame();
            ImGui.Begin("Demo windows");
            ImGui.Text("Hello world");
            ImGui.End();
            ImGui.Render();

            gameWindow.SwapBuffers();
        }

        private static void GameWindow_Load()
        {
            GL.ClearColor(Color4.CornflowerBlue);

            ImGui.CreateContext();
            ImGuiIOPtr io = ImGui.GetIO();
            ImGui.StyleColorsDark();
        }
    }
}