Added helper method for selecting the debug build variant.

Mochi.DearImGui/MochiDearImGui.cs

@@ -0,0 +1,65 @@
+using System;
+using System.IO;
+using System.Reflection;
+using System.Runtime.InteropServices;
+
+namespace Mochi.DearImGui;
+
+public static class MochiDearImGui
+{
+    public enum Variant
+    {
+        Default,
+        Debug,
+        Release,
+    }
+
+    private static IntPtr NativeRuntimeHandle;
+
+    // This could be public, but it's very hard to use correctly and the developer could currently manually set their own import resolver.
+    // Let's wait to expose this based on a demonstrated need so that the API can stay flexible and so if someone thinks/knows they need this they'll feel more inclined to say something.
+    /// <summary>Specifies a specific <see cref="NativeLibrary"/> handle to use for the Dear ImGui runtime.</summary>
+    /// <remarks>You must call this method before calling any Dear ImGui functions.</remarks>
+    private static void UseSpecificRuntime(IntPtr nativeRuntimeHandle)
+    {
+        if (nativeRuntimeHandle == IntPtr.Zero)
+        { throw new ArgumentException("The specified native runtime handle is invalid.", nameof(nativeRuntimeHandle)); }
+        else if (NativeRuntimeHandle != IntPtr.Zero)
+        { throw new InvalidOperationException("Cannot select a specific runtime after one has already been loaded."); }
+
+        //TODO: We should validate that the native runtime wasn't already loaded
+        NativeRuntimeHandle = nativeRuntimeHandle;
+
+        static IntPtr DllImportResolver(string libraryName, Assembly assembly, DllImportSearchPath? searchPath)
+            => NativeRuntimeHandle;
+
+        NativeLibrary.SetDllImportResolver(typeof(MochiDearImGui).Assembly, DllImportResolver);
+    }
+
+    /// <summary>Specifies a specific variant of the Dear ImGui runtime to use.</summary>
+    /// <remarks>
+    /// You must call this method before calling any Dear ImGui functions.
+    ///
+    /// In order to use a variant, you must manually add the appropriate NuGet package reference.
+    /// (For example: To use the debug variant on Windows x64, reference the appropriate version of Mochi.DearImGui.Native.win-x64-debug.)
+    ///
+    /// This method expects the native runtime layout file provided by the official MochiDearImGui NuGet packages.
+    /// </remarks>
+    public static void SelectRuntimeVariant(Variant variant)
+    {
+        string variantPath = "Mochi.DearImGui.Native";
+
+        variantPath = variant switch
+        {
+            Variant.Default => variantPath,
+            Variant.Release => variantPath,
+            Variant.Debug => Path.Combine("debug", variantPath),
+            _ => throw new ArgumentException("The specified variant is invalid.", nameof(variant))
+        };
+
+        if (NativeLibrary.TryLoad(variantPath, typeof(MochiDearImGui).Assembly, DllImportSearchPath.ApplicationDirectory, out IntPtr handle))
+        { UseSpecificRuntime(handle); }
+        else
+        { throw new DllNotFoundException($"Failed to load the {variant.ToString().ToLowerInvariant()} variant of the Dear ImGui runtime '{variantPath}'. Is the appropriate runtime NuGet package installed?"); }
+    }
+}