error.cs

using System;
using System.Runtime.InteropServices;

namespace ConsoleApp1
{
	unsafe class Program
	{
		private static readonly IntPtr libSkiaSharp;

		static Program()
		{
			libSkiaSharp = Win32.LoadLibrary(@"C:\Users\mattl\.nuget\packages\skiasharp\2.80.1\runtimes\win-x86\native\libSkiaSharp.dll");
		}

		static void Main(string[] args)
		{
			var font = sk_font_new();

			var res = sk_font_measure_text(font, null, IntPtr.Zero, 0, IntPtr.Zero, IntPtr.Zero);

			Console.WriteLine(res);
		}

		internal static IntPtr sk_font_new()
		{
			var proc = Win32.GetProcAddress(libSkiaSharp, "sk_font_new");
			var del = Marshal.GetDelegateForFunctionPointer<Delegates.sk_font_new>(proc);
			return del.Invoke();
		}

		internal static float sk_font_measure_text(IntPtr font, void* text, IntPtr byteLength, int encoding, IntPtr bounds, IntPtr paint)
		{
			var proc = Win32.GetProcAddress(libSkiaSharp, "sk_font_measure_text");
			var del = Marshal.GetDelegateForFunctionPointer<Delegates.sk_font_measure_text>(proc);
			return del.Invoke(font, text, byteLength, encoding, bounds, paint);
		}

		private partial class Delegates
		{
			[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
			internal delegate IntPtr sk_font_new();

			[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
			internal delegate Single sk_font_measure_text(IntPtr font, void* text, IntPtr byteLength, int encoding, IntPtr bounds, IntPtr paint);
		}
	}

	public static class Win32
	{
		private const string SystemLibrary = "Kernel32.dll";

		[DllImport(SystemLibrary, SetLastError = true, CharSet = CharSet.Ansi)]
		public static extern IntPtr LoadLibrary(string lpFileName);

		[DllImport(SystemLibrary, SetLastError = true, CharSet = CharSet.Ansi)]
		public static extern IntPtr GetProcAddress(IntPtr hModule, string lpProcName);

		[DllImport(SystemLibrary, SetLastError = true, CharSet = CharSet.Ansi)]
		public static extern void FreeLibrary(IntPtr hModule);
	}
}