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) {}
Hello
try to use AnyType:
AnyType providerObj = _provider;
if (providerObj is new ExchangeRateProviderCBOE) {
}
Oops
AnyType providerObj = _provider;
if (providerObj is ExchangeRateProviderCBOE) {
For ElectronicReporting we added ERCast class just to make it easier:
if (ERCast::asObject(providerObj) is ExchangeRateProviderCBOE) {
Good idea! Using anytype does work (the correct syntax is if (providerObj is new ExchangeRateProviderCBOE)).
I don’t see the point in using ERCast::asObject(), but ERCast::asAny() indeed makes things simpler, since we don’t have to declare any anytype variable. The downside is taking dependency on the ER module; it would be nice to have such things in the platform or a general-purpose library.
By the way, there are already people like Peter Villadsen involved and it seems that X++ compiler will be extended to support this scenario. 🙂
ERCast::asObject is for cases when one need to cast CLR interface to X++ object like
void myCode(IDisposable _x)
{
if (_x is MyXppClass) // does not compile
if (ERCast::asObject(_x) is MyXppClass) // compiles
}
Maybe it is fixed already but did not work in 7.3
Aha, you’re right. For some reason (that I’m unable to explain), I thought that asObject() does something else.