我正在使用反射构建动态方法。大多数教程和文档(例如如何:定义和定义执行动态方法或动态创建方法并执行)显示一个非常简单的示例。
I am building a dynamic method using reflection. Most tutorials and documentation (e.g. How to: Define and Execute Dynamic Methods or Creating method dynamically, and executing it) show a very simple example.
我试图找到一种从动态程序集中引用另一个程序集的方法。
I trying to find a way to reference another assembly from the dynamic assembly.
例如,我希望能够通过使用 Reflection.Emit 构造以下函数。
For example, I would like to be able to construct the following function by using Reflection.Emit.
public static void f(int n) { int[] arr = new arr[n]; return arr.Max(); }这样做的常见方式是什么?
What would be the common way of doing this?
推荐答案获取有效IL指令的最可靠方法是用高级语言创建代码,对其进行编译和反编译。接下来,您可以使用 Reflection.Emit 重新创建指令。
The most reliable way to get valid IL instructions is to create your code in a high level language, compile it and decompile it. Next you can recreate the instructions with Reflection.Emit.
我更改了示例函数,否则它的可测试性不好,因为结果将始终相同:
I changed your example function otherwise its not good testable because the result would be always the same:
public static int f(int n) { int[] arr = Enumerable.Range(0, n).ToArray(); return arr.Max(); }作为调试程序构建,ILDAsm给了我们(释放将导致更少的指令,但是
Build as debug, ILDasm gives us (Release would result in far fewer instructions but there is not too much to see then):
.method public hidebysig static int32 f(int32 n) cil managed { // Code size 25 (0x19) .maxstack 2 .locals init ([0] int32[] arr, [1] int32 V_1) IL_0000: nop IL_0001: ldc.i4.0 IL_0002: ldarg.0 IL_0003: call class [mscorlib]System.Collections.Generic.IEnumerable`1<int32> [System.Core]System.Linq.Enumerable::Range(int32, int32) IL_0008: call !!0[] [System.Core]System.Linq.Enumerable::ToArray<int32>(class [mscorlib]System.Collections.Generic.IEnumerable`1<!!0>) IL_000d: stloc.0 IL_000e: ldloc.0 IL_000f: call int32 [System.Core]System.Linq.Enumerable::Max(class [mscorlib]System.Collections.Generic.IEnumerable`1<int32>) IL_0014: stloc.1 IL_0015: br.s IL_0017 IL_0017: ldloc.1 IL_0018: ret } // end of method Program::f现在,您可以使用MethodBuilder / DynamicMethod和ILGenerator重新创建此方法的每个方面。
Now you can recreate every aspect of this method with the MethodBuilder/DynamicMethod and the ILGenerator.
public static int fNew(int n) { var da = AppDomain.CurrentDomain.DefineDynamicAssembly(new AssemblyName("tempAsm"), AssemblyBuilderAccess.RunAndSave); var dm = da.DefineDynamicModule("tempAsm", "tempAsm.dll"); var dt = dm.DefineType("dynType"); var d = dt.DefineMethod("f", MethodAttributes.Public | MethodAttributes.Static | MethodAttributes.HideBySig, CallingConventions.Standard, typeof (int), new[] {typeof (int)}); var il = d.GetILGenerator(); il.DeclareLocal(typeof (int[])); il.DeclareLocal(typeof (int)); var range = typeof (Enumerable).GetMethod(nameof(Enumerable.Range)); var toArray = typeof (Enumerable).GetMethod(nameof(Enumerable.ToArray)).MakeGenericMethod(typeof (int)); var max = typeof (Enumerable).GetMethod(nameof(Enumerable.Max), new[] {typeof (IEnumerable<>).MakeGenericType(typeof (int))}); if (range == null || toArray == null || max == null) throw new Exception(); var branchTarget = il.DefineLabel(); il.Emit(OpCodes.Nop); il.Emit(OpCodes.Ldc_I4_0); il.Emit(OpCodes.Ldarg_0); il.Emit(OpCodes.Call, range); il.Emit(OpCodes.Call, toArray); il.Emit(OpCodes.Stloc_0); il.Emit(OpCodes.Ldloc_0); il.Emit(OpCodes.Call, max); il.Emit(OpCodes.Stloc_1); il.Emit(OpCodes.Br_S, branchTarget); il.MarkLabel(branchTarget); il.Emit(OpCodes.Ldloc_1); il.Emit(OpCodes.Ret); var bakedType = dt.CreateType(); da.Save("tempAsm.dll"); var x = bakedType.GetMethod("f"); return (int) x.Invoke(null, new object[] {n}); }测试一下:
static void Main(string[] args) { Console.WriteLine(f(10)); Console.WriteLine(fNew(10)); },它应该可以工作:
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