从IL构造方法引用集合 [英] Reference a collection from IL constructed method
问题描述
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:
9
9
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