Imagine you have large DTOs that are ushared for GET, POST and PUT.

Some properties might only be used for display purposes, and cannot be updated (i.e. denormalized fields).

You might also allow the setting of a property on POST, but not on PUT. For example, you might not allow the Id of an object to be set on POST (because it will be the primary key identity insert), but if you want to update it, you can pass it in a PUT:

We currently are doing this using a custom attribute and interface on the models and model properties.

[ReadonlyRequest(ApplyTo.Post, null)]
public int? Id { get; set; }

Before each request we build up a list of warnings that we add to the request context. We also remove / set the default on any properties using this attribute.

After the request is processed, we automatically add a list of warnings to the ResponseStatus.

The calling client then knows based on the response, which of the data they have passed will simply be ignored.

When creating immutable objects, it's common to not have a default constructor. ServiceStack.Text supports this presently with the use of FormatterServices.GetUnitializedObject. However, GetUnitializedObject does not do any field initialization. The DataContractSerializer works around this with support of the OnDeserialized attribute; but why would we want to write the initialization code twice? Instead, We should change ServiceStack.Text to fall back to private constructors. Here is some proposed code.

public static ConstructorInfo GetEmptyConstructor(this Type type)
{
#if NETFX_CORE
return type.GetTypeInfo().DeclaredConstructors.FirstOrDefault(c => c.GetParameters().Count() == 0);
#else
var ret = type.GetConstructor(Type.EmptyTypes);
if (ret != null) return ret;

// attempt to use constructors with all default values
var ctors = from ctor in type.GetConstructors()
let prms = ctor.GetParameters()
where prms.All(p => p.IsOptional)
orderby prms.Length
select ctor;

ret = ctors.FirstOrDefault();
if (ret != null) return ret;

if (JsConfig.UsePrivateConstructor)
{
ret = type.GetConstructor(BindingFlags.Instance | BindingFlags.NonPublic, null, Type.EmptyTypes, null);
}

return ret;
#endif
}