.NET Interoperability Tricks: Dynamics NAV: Generic Lists<​T> in C/AL

Working with .NET in Dynamics NAV 2018 is cool. It feels like you are writing C/AL armed with the full might and strength of an Asgardian god. There is a good amount of tutorials online that help us understand how this interoperability works.

Recently, I was in need to model a List<T> where T could be any type of class. I will demonstrate how this can be achieved. As an example, we will attempt to model a NAV Purchase Order and NAV Purchase Lines.

Step 1: Create a .NET Standard Class Library in Visual Studio

Step Two: The Purchase Order Class and Purchase Lines Class

Step Three: The C/AL Code

PurchaseOrder := PurchaseOrder.NAVPurchasOrder();

PurchaseOrder.DocumentType := ‘Order’;

PurchaseOrder.No := ‘PO1000’;

Now its time to set values for our Items. But how do we do that? Lets say there are 2 Items in this PO. We would first have to

REPEAT

//Somehow add NAV Items to a List<NAVItems>

UNTIL NAVPurchaseLine.NEXT = 0

First, we need a List Variable:

NavItemsList: System.Collections.Generic.List`1.’mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'

Next, we need to Tell NAV that this List is of type dotnet NAVPurchaseLines. To do this, I figured out a quick and easy way using the NavItemsList constructor. C/AL will make this of Type whatever the constructor returns.

So in our Purchase Order class, we can create a function that returns a List<NAVPurchaseLines> as such:

public List<NAVPurchaseLines> InitializeNavPurchaseLines()

{

return new List<NAVPurchaseLines>();

}

in C/AL:

NavItemsList := PurchaseOrder. InitializeNavPurchaseLines();

Now we can loop through the Items:

NavItem: .NET Type of NAVLibrary.PurchaseLines

REPEAT

NavItem:=NavItem.NAVItem;

NavItem.DocumentType:= ‘Order’;

NavItem.BuyFromVendorNo:= ‘31314’;

NavItem.DocNo:= ‘PO1000’;

NavItem.LineNo:= ‘1000’;

NavItemsList.Add(NavItem);

UNTIL NAVPurchaseLine.NEXT = 0;

And Finally, we can add our NavItemsList to our Purchase Order class

Type := GETDOTNETTYPE(PurchaseOrder);

Type.GetProperty(‘PurchaseLines’).SetValue(PurchaseOrder,NavItemsList);

Which this technique, We are easily able to add Any Type of List to our Class from C/AL!

SO.MUCH.POWER