I want to build type dynamically like this:
public class Sample
{
Sample Parent { get; set; }
public Sample(Sample parent)
{
Parent = parent;
}
public int Depth
{
get
{
if (Parent == null)
return -1;
else
return Parent.Depth + 1;
}
}
}
The code I write is :
const string assemblyName = "SampleAssembly";
const string parentPproperty = "Parent";
const string depthProperty = "Depth";
const string typeName = "Sample";
const string assemblyFileName = assemblyName + ".dll";
AppDomain domain = AppDomain.CurrentDomain;
AssemblyBuilder assemblyBuilder = domain.DefineDynamicAssembly(new AssemblyName(assemblyName), AssemblyBuilderAccess.RunAndSave);
ModuleBuilder moduleBuilder = assemblyBuilder.DefineDynamicModule(assemblyName, assemblyFileName);
TypeBuilder typeBuilder = moduleBuilder.DefineType(typeName, TypeAttributes.Public);
FieldBuilder parentField = typeBuilder.DefineField($"_{parentPproperty}", typeBuilder, FieldAttributes.Private);
PropertyBuilder propertyBuilder = typeBuilder.DefineProperty(parentPproperty, PropertyAttributes.None, parentField.FieldType, Type.EmptyTypes);
MethodAttributes getSetAttr = MethodAttributes.Public |
MethodAttributes.SpecialName | MethodAttributes.HideBySig;
MethodBuilder getParentMethod = typeBuilder.DefineMethod($"get_{propertyBuilder.Name}", getSetAttr, parentField.FieldType, Type.EmptyTypes);
ILGenerator il = getParentMethod.GetILGenerator();
il.Emit(OpCodes.Ldarg_0);
il.Emit(OpCodes.Ldfld, parentField);
il.Emit(OpCodes.Ret);
propertyBuilder.SetGetMethod(getParentMethod);
MethodBuilder setParentMethod = typeBuilder.DefineMethod($"set_{propertyBuilder.Name}", qetSetAttr, null, Type.EmptyTypes);
il = setParentMethod.GetILGenerator();
il.Emit(OpCodes.Ldarg_0);
il.Emit(OpCodes.Ldarg_1);
il.Emit(OpCodes.Stfld, parentField);
il.Emit(OpCodes.Ret);
propertyBuilder.SetSetMethod(setParentMethod);
parentField = typeBuilder.DefineField($"_{depthProperty}", typeBuilder, FieldAttributes.Private);
propertyBuilder = typeBuilder.DefineProperty(depthProperty, PropertyAttributes.None, parentField.FieldType, Type.EmptyTypes);
MethodBuilder getDepthMethod = typeBuilder.DefineMethod($"get_{depthProperty}", getSetAttr , parentField.FieldType, Type.EmptyTypes);
il = getDepthMethod.GetILGenerator();
LocalBuilder lb = il.DeclareLocal(typeof(bool));
il.Emit(OpCodes.Ldarg_0);
il.Emit(OpCodes.Call, getParentMethod);
il.Emit(OpCodes.Ldnull);
il.Emit(OpCodes.Ceq);
il.Emit(OpCodes.Stloc_0);
il.Emit(OpCodes.Ldloc_0);
il.Emit(OpCodes.Brfalse_S);
il.Emit(OpCodes.Ldc_I4_1);
il.Emit(OpCodes.Stloc_1);
il.Emit(OpCodes.Br_S);
il.Emit(OpCodes.Ldarg_0);
il.Emit(OpCodes.Call, getParentMethod);
il.Emit(OpCodes.Callvirt, getDepthMethod);
il.Emit(OpCodes.Ldc_I4_1);
il.Emit(OpCodes.Add);
il.Emit(OpCodes.Stloc_1);
il.Emit(OpCodes.Br_S);
il.Emit(OpCodes.Ldloc_1);
il.Emit(OpCodes.Ret);
propertyBuilder.SetGetMethod(getDepthMethod);
ConstructorBuilder constructor = typeBuilder.DefineConstructor(MethodAttributes.Public, CallingConventions.HasThis, new Type[] { typeBuilder });
il= constructor.GetILGenerator();
il.Emit(OpCodes.Ldarg_0);
il.Emit(OpCodes.Call, typeof(object).GetConstructor(Type.EmptyTypes));
il.Emit(OpCodes.Ldarg_0);
il.Emit(OpCodes.Ldarg_1);
il.Emit(OpCodes.Call, setParentMethod);
il.Emit(OpCodes.Ret);
Type type = typeBuilder.CreateType();
var obj1 = Activator.CreateInstance(type, null);
var obj2 = Activator.CreateInstance(type, obj1);
assemblyBuilder.Save(assemblyFileName);
I think I had problem in building constructor and Depth property getter method.
Please help me get out of this.
Instance is not created as well.
Thanks
There are a few issues in your code.
In your parent setter method, you missed to declare the parameter:
You are declaring a redundant backing field here, just delete this line:
Your depth property is of the wrong type, it has to be of type int:
The IL code you are generating for your computed property seems like debugging code, I replaced it with release code. Also, you are emitting incomplete branching instructions, you should pass a target label as second parameter, have a look at this working method body:
Last but not least, you have to wrap your null argument in an object array so that the activator can find the expected constructor overload: