问题
I want to create a multi-dimensional array using Reflection.Emit and set it's element. Like the following C# code:
int[,] nums = new int[2, 2];
nums[1, 1] = 2;
And turn into IL code:
IL_0000: nop
IL_0001: ldc.i4.2
IL_0002: ldc.i4.2
IL_0003: newobj instance void int32[0..., 0...]::.ctor(int32, int32)
IL_0008: stloc.0
IL_0009: ldloc.0
IL_000a: ldc.i4.1
IL_000b: ldc.i4.1
IL_000c: ldc.i4.2
IL_000d: call instance void int32[0..., 0...]::Set(int32, int32, int32)
The IL code to create array:
newobj instance void int32[0..., 0...]::.ctor(int32, int32)
And the IL code to set the array's element:
call instance void int32[0..., 0...]::Set(int32, int32, int32)
What kind of IL Generator.Emit() code corresponding to those two IL sentence?
回答1:
You can almost translate that IL verbally:
il.Emit(OpCodes.Ldc_I4_2);
il.Emit(OpCodes.Ldc_I4_2);
var constructor = typeof(int[,]).GetConstructor(new Type[]{ typeof(int), typeof(int) });
il.Emit(OpCodes.Newobj, constructor);
il.Emit(OpCodes.Stloc_0);
il.Emit(OpCodes.Ldloc_0);
il.Emit(OpCodes.Ldc_I4_1);
il.Emit(OpCodes.Ldc_I4_1);
il.Emit(OpCodes.Ldc_I4_2);
var setMethod = typeof(int[,]).GetMethod("Set");
il.Emit(OpCodes.Call, setMethod);
Of course, you need to use reflection to actually get the ConstructorInfo
and the MethodInfo
object you need for the Newobj
and Call
codes.
回答2:
Here is an example:
DynamicMethod method =
new DynamicMethod("Test" , typeof(int[,]), new Type[]{});
var generator = method.GetILGenerator();
//get the constructor that takes in 2 integers (the dimensions of the array)
var constructor = typeof (int[,])
.GetConstructor(new {typeof (int), typeof (int)});
//get the Set method that takes in 3 integers; 2 indexes and the value
var set_method = typeof(int[,])
.GetMethod("Set", new[] { typeof(int), typeof(int), typeof(int) });
var local = generator.DeclareLocal(typeof (int[,])); //local variable to reference the array
generator.Emit(OpCodes.Ldc_I4_2);
generator.Emit(OpCodes.Ldc_I4_2);
generator.Emit(OpCodes.Newobj, constructor); //invoke the constructor to create the array
generator.Emit(OpCodes.Stloc, local);
generator.Emit(OpCodes.Ldloc, local);
generator.Emit(OpCodes.Ldc_I4_1);
generator.Emit(OpCodes.Ldc_I4_1);
generator.Emit(OpCodes.Ldc_I4_2);
generator.Emit(OpCodes.Call, set_method); //call the Set method to set the value
generator.Emit(OpCodes.Ldloc, local);
generator.Emit(OpCodes.Ret);
var result_method = (Func<int[,]>)method.CreateDelegate(typeof (Func<int[,]>));
var result = result_method(); //returns the array
This example creates a dynamic method that creates the array, fills the value in [1,1], and then returns that array.
来源:https://stackoverflow.com/questions/36250968/how-to-create-multi-dimensional-array-using-reflection-emit