cscの作法 その280

概要

cscの作法、調べてみた。
練習問題やってみた。

練習問題

Marshal.GetDelegateForFunctionPointerを使ってください。

方針

• dllimport使わない、dllインポート。

参考にしたページ

サンプルコード

using System;
using System.Runtime.InteropServices;

namespace App
{
	public class LateBinding : IDisposable {
		[DllImport("kernel32", CharSet = CharSet.Unicode, SetLastError = true)]
		private static extern IntPtr LoadLibrary([MarshalAs(UnmanagedType.LPWStr)] string lpFileName);
		[DllImport("kernel32", SetLastError = true)]
		private static extern bool FreeLibrary(IntPtr hModule);
		[DllImport("kernel32", CharSet = CharSet.Ansi, SetLastError = true, ExactSpelling = false)]
		private static extern IntPtr GetProcAddress(IntPtr hModule, [MarshalAs(UnmanagedType.LPStr)] string lpProcName);
		private IntPtr _module;
		public LateBinding(string filename) {
			_module = LateBinding.LoadLibrary(filename);
			if (_module != IntPtr.Zero) 
			{
				return;
			}
			int result = Marshal.GetHRForLastWin32Error();
			throw Marshal.GetExceptionForHR(result);
		}
		public Delegate GetDelegate(string procName, Type delegateType) {
			IntPtr ptr = LateBinding.GetProcAddress(_module, procName);
			if (ptr != IntPtr.Zero) 
			{
				Delegate d = Marshal.GetDelegateForFunctionPointer(ptr, delegateType);
				return d;
			}
			int result = Marshal.GetHRForLastWin32Error();
			throw Marshal.GetExceptionForHR(result);
		}
		public void Dispose() {
			if (_module != IntPtr.Zero) 
			{
				LateBinding.FreeLibrary(_module);
			}
		}
	}
	public delegate int MessageBox(IntPtr hwnd, [MarshalAs(UnmanagedType.LPWStr)] string text, [MarshalAs(UnmanagedType.LPWStr)] string Caption, int type);
	static class Program {
		[STAThread]
		static void Main() {
			using (LateBinding b = new LateBinding("user32.dll")) 
			{
				MessageBox m = (MessageBox) b.GetDelegate("MessageBoxW", typeof(MessageBox));
				m(IntPtr.Zero, "hello c#", "App", 0);
			}
		}
	}
}

以上。