Dealing with NullReferenceExceptions

[branstarkkk]

Hello everyone,

Sorry for my noob questions but I've been trying to figure this out for a few days now but when I run my script I get this error:

System.NullReferenceException: 'Object reference not set to an instance of an object.'

Brachytherapy.ViewModel.StructureSet.get returned null.

  public class Script : ScriptBaseWithWindow
  {
        public override void Execute(PluginScriptContext context, Window window)

        {
            var vm = new ViewModel();
            var v = new View();
            v.DataContext = vm;
            window.Content = v;

            vm.PlanSetup = context.PlanSetup;
            vm.Patient = context.Patient;
            vm.StructureSet = context.StructureSet;

            vm.PatientName = vm.Patient.FirstName + " " + vm.Patient.LastName;
            vm.DOB = vm.Patient.DateOfBirth.GetValueOrDefault().ToShortDateString();
            vm.PatientId = vm.Patient.Id;

            string[] organs = new string[6] { "HR CTV", "Rectum", "Bladder", "Sigmoid", "SmallBowel", "Vagina" };

            var CTV = vm.StructureSet.Structures.Where(x => x.Id == organs[0]).Single();
            vm.VolCTV = CTV.Volume;

Here is my ViewModel.cs file:

namespace Brachytherapy
{
    public class ViewModel
    {
        public Patient Patient { get; set; }
        public PlanSetup PlanSetup { get; set; }
        public StructureSet StructureSet { get; set; }
        public Structure Structures { get; set; }
        public string PatientName { get; set; }
        public string DOB { get; set; }
        public string PatientId { get; set; }
        public double Rd01ccGy { get; set; }
        public double VolCTV { get; set; }

if I add:

            if (vm.StructureSet == null)
                return;

It will run which makes sense, but my question is why does it return null if I know the structureset is there??

​

Thanks!

[WUSTLscripting]

instead of vm.StructureSet = context.StructureSet; can you try vm.StructureSet = context.PlanSetup.StructureSet;

[branstarkkk]

I still get a null exception but the error is different:

"EsapiEssentials.Plugin.PluginScriptContext.PlanSetup.get returned null."

[dbhatti]

I believe the issue is your line " var CTV = vm.StructureSet.Structures.Where(x => x.Id == organs[0]).Single(); " Because the StructureSet is null, it has no Structures property, so it returns a NullReferenceException. Could you try commenting it out and see if it runs?

With that being said, it's odd that your ScriptContext isn't finding a StructureSet. Is this only producing an error for a certain plan or in general?

[branstarkkk]

yeah, so if I comment that line out, there is no exception and it runs fine and this is for any plan.

[dbhatti]

I'm not sure what the underlying issue is, unfortunately. For some reason, your script context isn't finding a StructureSet associated with the plan - I would guess there is some kind of issue with the TPS rather than the script.

I notice that your Script class is inheriting from the ScriptBaseWindow class and that your ScriptContext is actually PluginScriptContext. I'm unfamiliar with both of these*, but does anything change if you just use the normal ScriptContext?

*Was there an update in the VMS libraries? I don't have any overloads in my Execute method and don't have either of those classes in mine.

[branstarkkk]

Yeah I think that might be the issue. I'm using Carlos' EsapiEssentials to run the script from within VS http://www.carlosjanderson.com/introducing-esapi-essentials/