goshoom: ‘is’ and ‘as’ operators with .NET types

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Источник: http://dev.goshoom.net/en/2020/05/is...h-net-objects/
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I recently ran into an unfortunate limitation of .NET Interop from X++ (in D365FO).
I wanted to check if an X++ object is of a given type, nevertheless the type used for the variable declaration was a .NET interface. Here is an example:

using Microsoft.Dynamics.ApplicationSuite.FinancialManagement.Currency.Framework; void demo(IExchangeRateProvider _provider){ if (_provider is ExchangeRateProviderCBOE) {}}






Exchange rate providers are X++ classing implementing IExchangeRateProvider interface and I wanted to check if the object I received was a particular provider (namely ExchangeRateProviderCBOE class or its child). Unfortunately this ended up with a compilation error:

The operand on the left side of the ‘is’ or ‘as’ operator must be a table, class, or form.

As I tested, neither managed interfaces nor managed classes (such as System.Object) can be used on the left side of ‘is’ and ‘as’ operators.

I solved the problem by using Type.IsAssignableFrom() method. Simply using the ‘is’ operator would be nicer, but this does the job too.

void demo(IExchangeRateProvider _provider){ System.Object providerObj = _provider; if (providerObj.GetType().IsAssignableFrom(new ExchangeRateProviderCBOE().GetType())) {}}






Note that the problem is only with the left side of the operators, e.g. when you want to check whether a managed type is this or that. Using the ‘is’ operator to check if an instance of an X++ class implements a managed interface works without problems.

Object obj = new ExchangeRateProviderCBOE();if (obj is IExchangeRateProvider) {}








Источник: http://dev.goshoom.net/en/2020/05/is...h-net-objects/

[belugin]

Мы пользуемся AnyType и сделали себе класс ERCast чтобы обходить это:

AnyType x;
if (x is System.IServiceProvider)
...
XppClass x
if (ERCast::asAny(x) is IDisposable)
...