Dynamics GP Web Services: Changing policy behavior at runtime - microsoft-dynamics

Question

I am creating a payables invoices using Web Services on GP2013. Optionally, my users can provide line item distributions. I can create invoices, but unless I modify the CreatePayablesInvoice policy to "Distributions Will Be Provided" in the dynamics security console, the invoice gets both the system provided distributions as well as the distribution lines I am creating. I want to have the ability to provide distributions if necessary, otherwise I want the system to handle it.
The documentation suggests I should be able to alter the policy in code, but when I get the policy object back from GetPolicyByOperation, the Behaviors array is empty. I have tried creating the behavior manually in code and it doesn't alter what happens when the invoice is created. The only thing that impacts the result is editing the property in the security console.
My code for altering the the policy is below:
payablesInvoiceCreatePolicy = wsDynamicsGP.GetPolicyByOperation("CreatePayablesInvoice", context);
BehaviorKey bk = new BehaviorKey();
bk.Id = new Guid("e476a157-ecf0-4dae-8cef-317dd2cfbe41");
Behavior b = new Behavior();
b.Key = bk;
BehaviorOption opt0 = new BehaviorOption();
opt0.Key = new BehaviorOptionKey();
opt0.Key.Id = 0;
opt0.Name = "Distributions Will Be Provided";
BehaviorOption opt1 = new BehaviorOption();
opt1.Key = new BehaviorOptionKey();
opt1.Key.Id = 1;
opt1.Name = "Automatically Create Distributions";
b.Options = new BehaviorOption[] { opt0, opt1 };
b.SelectedOption = b.Options[1];
payablesInvoiceCreatePolicy.Behaviors = new Behavior[]{b};
wsDynamicsGP.CreatePayablesInvoice(payablesInvoice, context, payablesInvoiceCreatePolicy);
Documentation seems to be sparse on what should or shouldn't work here. I have to assume I should be able to update the policy as I see fit at runtime based on whether or not my user has decided to provide line item distributions.
Does anyone know what I am missing?

Answer 1

Yes. It took me 2 days to fix this myself. After adding the behaviour to the policy object UpdatePolicy before calling the create invoice as below:
wsDynamicsGP.UpdatePolicy(payablesInvoiceCreatePolicy, new RoleKey { Id = "00000000-0000-0000-0000-000000000000" }, context)
wsDynamicsGP.CreatePayablesInvoice(payablesInvoice, context, payablesInvoiceCreatePolicy);

Answer 2

Note that you selected the behavior that automatically creates distribution lines on invoice creation. The behavior's Internal property also must be set to true.
Here is a working example also utilizing FlowerKing's answer:
BehaviorKey bk = new BehaviorKey();
bk.Id = new Guid("e476a157-ecf0-4dae-8cef-317dd2cfbe41");
bk.PolicyKey = payablesInvoiceCreatePolicy.Key;
Behavior b = new Behavior();
b.Key = bk;
b.Internal = true;
BehaviorOption opt0 = new BehaviorOption();
opt0.Key = new BehaviorOptionKey();
opt0.Key.Id = 0;
opt0.Name = "Distributions Will Be Provided";
BehaviorOption opt1 = new BehaviorOption();
opt1.Key = new BehaviorOptionKey();
opt1.Key.Id = 1;
opt1.Name = "Automatically Create Distributions";
b.Options = new BehaviorOption[] { opt0, opt1 };
b.SelectedOption = b.Options[0];
policy.Behaviors = new Behavior[] { b };
client.UpdatePolicy(payablesInvoiceCreatePolicy, new RoleKey { Id = "00000000-0000-0000-0000-000000000000" }, context);
client.CreatePayablesInvoice(payablesInvoice, context, payablesInvoiceCreatePolicy);