CRM 2013: Using the value of an Option Set input parameter in a custom workflow activity

Question

I was trying to use an optionset input parameter in custom workflow activity, so I have used the below code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Security.Cryptography;

using System.Activities;
using Microsoft.Xrm.Sdk;
using Microsoft.Xrm.Sdk.Workflow;
using Microsoft.Xrm.Sdk.Query;
using System.Globalization;

namespace ITWorx.VisitManagement.Workflows
{
    public class FormatDate : CodeActivity
    {
        [Input("Preferred Language")]
        [AttributeTarget("contact", "itworx_preferredlanguage")]
        [Default("894330000")]
        public InArgument<OptionSetValue> PreferredLanguage { get; set; }

        protected override void Execute(CodeActivityContext context)
        {
            IWorkflowContext workflowContext = context.GetExtension<IWorkflowContext>();
            IOrganizationServiceFactory serviceFactory = context.GetExtension<IOrganizationServiceFactory>();
            IOrganizationService service = serviceFactory.CreateOrganizationService(workflowContext.UserId);

            int preferredLanguage = PreferredLanguage.Get<OptionSetValue>(context).Value;

        }
    }
}

But an exception is thrown in the below line:

int preferredLanguage = PreferredLanguage.Get<OptionSetValue>(context).Value;

Exception: NullReferenceException {"Object reference not set to an instance of an object."}

Please advise

Answer 1

The Default("894330000") attribute does not generate a Default value in code, it only tells the Workflow designer what to suggest as a Value. When you set the Value to a Dynamic Value, based on your entity record (which I assume you are doing, you must set the Default Value at that time. This is what it should look like in your Workflow editor:

You can also modify your code to ensure that if a null value does get passed it will use your desired default:

int preferredLanguage = PreferredLanguage.Get<OptionSetValue>(context) != null
            ? PreferredLanguage.Get<OptionSetValue>(context).Value
            : 894330001;

Answer 2

PreferredLanguage.Get<OptionSetValue>(context) yields an OptionSetValue object.

OptionSetValue is a class and can therefore be null.

My best guess: field itworx_preferredlanguage is null for the given record. Trying to get its .Value property throws the NullReferenceException.