使用 C# 4.0 dynamic 让 PInvoke 变简单

http://tirania.org/blog/archive/2009/Aug-11.html的文章中介绍了一种使用dynamic对象调用PInvoke的方法，笔者在这些代码的基础上作了一些改进，添加了返回值和ref及out类型参数的支持。

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Dynamic;using System.Reflection;using System.Linq.Expressions;using System.Reflection.Emit;using System.Threading;namespace RaisingStudio{ internal class DynamicDllImportMetaObject : DynamicMetaObject { public DynamicDllImportMetaObject(Expression expression, object value) : base(expression, BindingRestrictions.Empty, value) { } public override DynamicMetaObject BindInvokeMember(InvokeMemberBinder binder, DynamicMetaObject[] args) { Type returnType = GetMethodReturnType(binder); Type[] types = new Type[args.Length]; Expression[] arguments = new Expression[args.Length]; for (int i = 0; i < args.Length; i++) { Type type = args[i].LimitType; Expression expression = args[i].Expression; dynamic typedParameterExpression = expression; if (typedParameterExpression.IsByRef) { types[i] = type.MakeByRefType(); } else { types[i] = type; } arguments[i] = expression; } MethodInfo method = (base.Value as DynamicDllImport).GetInvokeMethod(binder.Name, returnType, types); Expression callingExpression; if (method.ReturnType == typeof(void)) { callingExpression = Expression.Block(Expression.Call(method, arguments), Expression.Default(typeof(object))); } else { callingExpression = Expression.Convert(Expression.Call(method, arguments), typeof(object)); } BindingRestrictions bindingRestrictions = BindingRestrictions.GetTypeRestriction(this.Expression, typeof(DynamicDllImport)); return new DynamicMetaObject(callingExpression, bindingRestrictions); } private Type GetMethodReturnType(InvokeMemberBinder binder) { IList<Type> types = binder.GetType().GetField("m_typeArguments", BindingFlags.NonPublic | BindingFlags.Instance).GetValue(binder) as IList<Type>; if ((types != null) && (types.Count > 0)) { return types[0]; } return null; } } public class DynamicDllImport : DynamicObject { internal string dllName; public string DllName { get { return dllName; } } public System.Runtime.InteropServices.CharSet CharSet = System.Runtime.InteropServices.CharSet.Auto; public System.Runtime.InteropServices.CallingConvention CallingConvention = System.Runtime.InteropServices.CallingConvention.Cdecl; public DynamicDllImport(string dllName) { this.dllName = dllName; } public DynamicDllImport(string dllName, System.Runtime.InteropServices.CharSet charSet = System.Runtime.InteropServices.CharSet.Auto, System.Runtime.InteropServices.CallingConvention callingConvention = System.Runtime.InteropServices.CallingConvention.Cdecl) { this.dllName = dllName; this.CharSet = charSet; this.CallingConvention = callingConvention; } AssemblyBuilder assemblyBuilder; ModuleBuilder moduleBuilder; private string assemblyName; internal string AssemblyName { get { if (this.assemblyName == null) { this.assemblyName = GetAssemblyName(); } return this.assemblyName; } set { this.assemblyName = value; } } private string GetAssemblyName() { return (new System.IO.FileInfo(this.dllName)).Name; } private int methodIndex = 0; private string GetDefineTypeName(string methodName) { return string.Format("{0}_{1}", methodName, Interlocked.Increment(ref this.methodIndex)); } public override DynamicMetaObject GetMetaObject(System.Linq.Expressions.Expression parameter) { return new DynamicDllImportMetaObject(parameter, this); } public MethodInfo GetInvokeMethod(string methodName, Type returnType, Type[] types) { string entryName = methodName; if (assemblyBuilder == null) { AssemblyName assemblyName = new AssemblyName(AssemblyName); assemblyBuilder = AppDomain.CurrentDomain.DefineDynamicAssembly(assemblyName, AssemblyBuilderAccess.Run); moduleBuilder = assemblyBuilder.DefineDynamicModule(AssemblyName); } var defineType = moduleBuilder.DefineType(GetDefineTypeName(methodName)); var methodBuilder = defineType.DefinePInvokeMethod(methodName, dllName, entryName, MethodAttributes.Public | MethodAttributes.Static | MethodAttributes.PinvokeImpl, CallingConventions.Standard, returnType, types, CallingConvention, CharSet); if ((returnType != null) && (returnType != typeof(void))) { methodBuilder.SetImplementationFlags(MethodImplAttributes.PreserveSig | methodBuilder.GetMethodImplementationFlags()); } var type = defineType.CreateType(); var method = type.GetMethod(methodName, BindingFlags.Public | BindingFlags.Static); return method; } }}

示例:

dynamic user32 = new DynamicDllImport("user32.dll", callingConvention : CallingConvention.Winapi);user32.MessageBox(0, "Hello World", "Platform Invoke Sample", 0);dynamic asmproject = new DynamicDllImport("asmproject.dll");int value = asmproject.add<int>(3, 4);Console.WriteLine(value); dynamic sdl = new DynamicDllImport("SDL.dll", CharSet.Ansi);Sdl.SDL_Rect rect = new Sdl.SDL_Rect( 0, 0, (short)width, (short)height);int result = sdl.SDL_FillRect<int>(rgbSurfacePtr, ref rect, 0);Sdl.SDL_Event evt;while (sdl.SDL_WaitEvent(out evt) != 0){ if (evt.type == Sdl.SDL_QUIT) { break; }}

 

最新代码可在 http://code.google.com/p/dynamicdllimport/ 下载。