Como injetar chamada para System.Object.Equals com Mono.Cecil?
Usando o Mono.Cecil, quero reescrever a seguinte propriedade:
public string FirstName
{
get { return _FirstName; }
set
{
_FirstName = value;
}
}
para isso:
public string FirstName
{
get { return _FirstName; }
set
{
if (System.Object.Equals(_FirstName, value))
{
return;
}
_FirstName = value;
}
}
Este é apenas um trecho do que será a reescrita, mas é onde estou tendo um problema.
Usando o Refletor, vejo o código a seguir reescreve a propriedade conforme necessário, exceto a chamada para System.Object.Equals (). Se você espera que o código IL seja:
call bool [mscorlib]System.Object::Equals(object, object)
mas está sendo escrito como:
call instance void RewriteSharp.Person::.ctor()
O código para gravar a chamada para System.Object.Equals é:
setMethodWriter.InsertBefore(
firstExistingInstruction,
setMethodWriter.Create(OpCodes.Call, objectEqualsMethodReference));
O método usado para iniciar objectEqualsMethodReference é:
private static MethodReference GetSystemObjectEqualsMethodReference(
AssemblyDefinition assembly
)
{
var typeReference = assembly.MainModule.GetTypeReferences()
.Single(t => t.FullName == "System.Object");
var typeDefinition = typeReference.Resolve();
var methodDefinition = typeDefinition.Methods.Single(
m => m.Name == "Equals"
&& m.Parameters.Count == 2
&& m.Parameters[0].ParameterType.Name == "Object"
&& m.Parameters[1].ParameterType.Name == "Object"
);
return methodDefinition;
}
Parece-me que setMethodWriter.Create () ou GetSystemObjectEqualsMethodReference () está incorreto e nenhuma quantidade de depuração resolveu o problema.
A propriedade que está sendo gravada e o código para reescrever a propriedade têm o mesmo destino da estrutura. 3.5 e 4.0 falham.
Estou usando o ramo principalhttps://github.com/jbevain/cecil para construir o Mono.Cecil.
Listagem de código completa
using Mono.Cecil;
using Mono.Cecil.Cil;
using System;
using System.Linq;
namespace RewriteNotifyPropertyChanged
{
class Program
{
static void Main(string[] args)
{
var rewrite = "..\\RewriteSharp.dll";
var rewritten = "..\\RewritenSharp.dll";
var typeName = "Person";
var propertyName = "FirstName";
var assembly = AssemblyDefinition.ReadAssembly(rewrite);
var typeDefinition = assembly.MainModule.Types.Single(t => t.Name == typeName);
var propertyDefintion = typeDefinition.Properties
.Single(p => p.Name == propertyName);
var setMethodWriter = propertyDefintion.SetMethod.Body.GetILProcessor();
var backingFieldReference = GetBackingFieldReference(typeDefinition, propertyName);
var objectEqualsMethodReference = GetSystemObjectEqualsMethodReference(assembly);
var firstExistingInstruction = setMethodWriter.Body.Instructions[0];
setMethodWriter.InsertBefore(
firstExistingInstruction,
setMethodWriter.Create(OpCodes.Ldarg_0));
setMethodWriter.InsertBefore(
firstExistingInstruction,
setMethodWriter.Create(OpCodes.Ldfld, backingFieldReference));
setMethodWriter.InsertBefore(
firstExistingInstruction,
setMethodWriter.Create(OpCodes.Ldarg_1));
setMethodWriter.InsertBefore(
firstExistingInstruction,
setMethodWriter.Create(OpCodes.Call, objectEqualsMethodReference));
setMethodWriter.InsertBefore(
firstExistingInstruction,
setMethodWriter.Create(OpCodes.Brfalse_S, firstExistingInstruction));
setMethodWriter.InsertBefore(
firstExistingInstruction,
setMethodWriter.Create(OpCodes.Ret));
assembly.Write(rewritten, new WriterParameters { WriteSymbols = true });
Console.WriteLine("Done.");
Console.ReadKey();
}
private static MethodReference GetSystemObjectEqualsMethodReference(
AssemblyDefinition assembly
)
{
var typeReference = assembly.MainModule.GetTypeReferences()
.Single(t => t.FullName == "System.Object");
var typeDefinition = typeReference.Resolve();
var methodDefinition = typeDefinition.Methods.Single(
m => m.Name == "Equals"
&& m.Parameters.Count == 2
&& m.Parameters[0].ParameterType.Name == "Object"
&& m.Parameters[1].ParameterType.Name == "Object"
);
return methodDefinition;
}
private static FieldReference GetBackingFieldReference(
TypeDefinition typeDefinition,
string propertyName
)
{
var fieldName = "_" + propertyName;
var fieldReference = typeDefinition.Fields.Single(f => f.Name == fieldName);
return fieldReference;
}
}
}