Error with simple Acumatica contract soap api call - api

Question

I'm trying to get a simple Acumatica contract-based SOAP API Get() or GetList() call to work and all I'm getting is an error:
System.ServiceModel.FaultException: 'System.ArgumentNullException: Value cannot be null. Parameter name: model
See the code below. I first tried the REST API, but couldn't get around different issues (which I'll also probably add in another post). Any ideas what the error is referring to?
using (var soapClient = new ServiceReference1.DefaultSoapClient())
{
//Log in to Acumatica ERP
soapClient.Login
(
"admin",
"admin",
"Company",
null,
null
);
ServiceReference1.SalesOrder orderToFind = new
ServiceReference1.SalesOrder
{
CustomerID = new ServiceReference1.StringValue { Value = "2" },
OrderType = new ServiceReference1.StringValue { Value = "SO" },
OrderNbr = new ServiceReference1.StringValue { Value =
"SO001337" },
};
var getOrder = soapClient.Get(orderToFind);
var getOrders =
soapClient.GetList(orderToFind);
}
Acumatica v17.204.0019.

Answer 1

Just encountered the same error and a little ashamed to admit that solution appeared to be super simply for me: the binding was simply missing allowCookies="true" in app.config
Having enabled cookies, error ArgumentNullException: Value cannot be null. Parameter name: model got resolved:
<binding name="DefaultSoap" allowCookies="true" />

Answer 2

The solution for me was to add the WSDL as a ServiceReference instead of a WebReference, long story. Another thing to check might be the app.config to make sure it has the correct endpoint, bindings, etc. as per Acumatica documentation.

Answer 3

When searching for a record, one must always work with a proper variation of the [FieldType]Search type. In your case the orderToFind object should be declared as follows:
ServiceReference1.SalesOrder orderToFind = new ServiceReference1.SalesOrder
{
OrderType = new ServiceReference1.StringSearch { Value = "SO" },
OrderNbr = new ServiceReference1.StringSearch { Value = "SO001337" }
};
var getOrder = soapClient.Get(orderToFind);
To export orders for the given customer, you should define the ordersToFind object as follows:
ServiceReference1.SalesOrder ordersToFind = new ServiceReference1.SalesOrder
{
CustomerID = new ServiceReference1.StringSearch { Value = "2" },
};
var getOrders = soapClient.GetList(orderToFind);