private static Delegate CreateReadDelegate(
[NotNull] Type delegateType,
[NotNull] Type elementType)
{
Debug.Assert(delegateType != null);
Debug.Assert(elementType != null);
var method = new DynamicMethod(
$"{DynamicMethodPrefix}Read{elementType.Name}",
typeof(void),
// reader, namespaceUri
new[] { typeof(XmlReader), typeof(string), elementType },
elementType.Module);
ILGenerator generator = method.GetILGenerator();
generator.DeclareLocal(typeof(string));
generator.Emit(OpCodes.Ldarg_0);
generator.Emit(OpCodes.Ldstr, "key");
generator.EmitCall(OpCodes.Callvirt, Metadata.GetAttributeMethod, null);
generator.Emit(OpCodes.Stloc_0);
// We need to create the switch for each property
Label next = generator.DefineLabel();
Label @return = generator.DefineLabel();
bool first = true;
foreach (PropertySerializationInfo info in SerializationHelpers.GetAttributeProperties(elementType))
{
PropertyInfo property = info.Property;
if (!first)
{
generator.MarkLabel(next);
next = generator.DefineLabel();
}
first = false;
generator.Emit(OpCodes.Ldloc_0);
generator.Emit(OpCodes.Ldstr, info.Name);
generator.EmitCall(OpCodes.Call, Metadata.StringEqualsMethod, null);
// If false jump to next
generator.Emit(OpCodes.Brfalse, next);
// Do our stuff
if (!Metadata.TryGetReadContentMethod(property.PropertyType, out MethodInfo readMethod))
{
throw new NotSupportedException($"Property {property.Name} has a non supported type.");
}
// Do we have a set method?
MethodInfo setMethod = property.GetSetMethod();
if (setMethod is null)
{
throw new InvalidOperationException($"Property {property.DeclaringType}.{property.Name} has no setter.");
}
// reader.ReadXXX
generator.Emit(OpCodes.Ldarg_2); // element
generator.Emit(OpCodes.Ldarg_0); // reader
generator.Emit(OpCodes.Ldstr, "data");
generator.Emit(OpCodes.Ldarg_1); // namespace URI
// When writing scalar values we call member methods of XmlReader, while for array values
// we call our own static methods. These two types of methods seem to need different OpCode.
generator.EmitCall(
readMethod.DeclaringType == typeof(XmlReaderExtensions)
? OpCodes.Call
: OpCodes.Callvirt,
readMethod,
null);
generator.EmitCall(OpCodes.Callvirt, setMethod, null);
// Jump to do while
generator.Emit(OpCodes.Br, @return);
}
// We don't know this parameter.. we throw
generator.MarkLabel(next);
generator.Emit(OpCodes.Ldloc_0);
generator.Emit(OpCodes.Newobj, Metadata.ArgumentExceptionCtor);
generator.Emit(OpCodes.Throw);
generator.MarkLabel(@return);
generator.Emit(OpCodes.Ret);
// Let's bake the method
return(method.CreateDelegate(delegateType));
}
