Reflection.Emit 抛出 BadImageFormatException

Question

我正在尝试在运行时生成一个新的 class/object。

阅读后，我已经设法实现了所有功能，一切都像我需要的那样。

但是当我尝试实例化我的新对象时，我收到了 BadImageFormatException

这似乎是一个类似的问题，但未解决Is there any way to instrument System.Reflection.Emit?

这是我的代码：

字段：

internal class Field {
      public string FieldName;
      public Type FieldType;
      public string Value;
    }

生成器代码：

var xx = new List<Field>(new[] { new Field { FieldName = "Name", FieldType = typeof(string), Value = "Hello World" },
        new Field { FieldName = "Id", FieldType = typeof(int), Value = "1" } });
      this.DoVodoo(xx);

魔术

private dynamic DoVodoo(IEnumerable<Field> fields) {
      var aName = new AssemblyName("DynamicAssemblyExample");
      var ab = AppDomain.CurrentDomain.DefineDynamicAssembly(aName, AssemblyBuilderAccess.RunAndSave);

      var mb = ab.DefineDynamicModule(aName.Name, aName.Name + ".dll");

      // Create class with all needed Properties
      var tb = mb.DefineType("ParamRow", TypeAttributes.Public, typeof(object));
      foreach (var field in fields) {
        var pb = tb.DefineProperty(field.FieldName, PropertyAttributes.None, CallingConventions.HasThis, field.FieldType, null);

        var getSetAttr = MethodAttributes.Public | MethodAttributes.SpecialName | MethodAttributes.HideBySig;
        // Define the "get" accessor method for the Property.
        var custNameGetPropMthdBldr = tb.DefineMethod($"get_{field.FieldName}", getSetAttr, typeof(string), Type.EmptyTypes);

        var custNameGetIL = custNameGetPropMthdBldr.GetILGenerator();

        custNameGetIL.Emit(OpCodes.Ldarg_0);
        custNameGetIL.Emit(OpCodes.Ldfld, custNameGetPropMthdBldr);
        custNameGetIL.Emit(OpCodes.Ret);

        // Define the "set" accessor method for CustomerName.
        var custNameSetPropMthdBldr = tb.DefineMethod($"set_{field.FieldName}", getSetAttr, null, new[] { typeof(string) });

        var custNameSetIL = custNameSetPropMthdBldr.GetILGenerator();

        custNameSetIL.Emit(OpCodes.Ldarg_0);
        custNameSetIL.Emit(OpCodes.Ldarg_1);
        //custNameSetIL.Emit(OpCodes.Stfld, custNameGetPropMthdBldr);
        custNameSetIL.Emit(OpCodes.Stfld, custNameSetPropMthdBldr);
        custNameSetIL.Emit(OpCodes.Ret);

        // Last, we must map the two methods created above to our PropertyBuilder to 
        // their corresponding behaviors, "get" and "set" respectively. 
        pb.SetGetMethod(custNameGetPropMthdBldr);
        pb.SetSetMethod(custNameSetPropMthdBldr);
      }

      var finalType = tb.CreateType();

      var result = new List<object>();

      foreach (var field in fields) {
        var inst = ab.CreateInstance(finalType.Name);
        finalType.GetProperty(field.FieldName, BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic).SetValue(inst, field.Value); //<-- Here comes the trouble
        result.Add(inst);
      }
      return result;}

感谢任何有关如何实例化我新创建的类型的帮助 ParamRow。

奖金问题：为什么会有BadImageFormatException?

附加信息：

.Net-Framework 4.6.1
编译器目标是 x86
以前Reflection.Emit从来没有

Answer 1

你得到的异常的.Message是重要的一点：

Field token out of range.

这告诉您它不理解您要在 ldfld / stfld 中使用的字段 - 这是因为您正在向它传递方法标记 (custNameGetPropMthdBldr / custNameSetPropMthdBldr) 而不是字段标记。

您需要定义和使用一个字段：

var fb = tb.DefineField("__" + field.FieldName, field.FieldType, FieldAttributes.Private);
// ...
custNameGetIL.Emit(OpCodes.Ldarg_0);
custNameGetIL.Emit(OpCodes.Ldfld, fb);
custNameGetIL.Emit(OpCodes.Ret);
// ...
custNameSetIL.Emit(OpCodes.Ldarg_0);
custNameSetIL.Emit(OpCodes.Ldarg_1);
custNameSetIL.Emit(OpCodes.Stfld, fb);
custNameSetIL.Emit(OpCodes.Ret);

另请注意，通过反射创建对象时，使用 Type 比 name 更有效；这很好用：

var inst = Activator.CreateInstance(finalType);

Reflection.Emit 抛出 BadImageFormatException

Reflection.Emit throws BadImageFormatException

c#

reflection

reflection.emit