Silverlight WCF/RIA MVVM Property

Question

I've got a Property built in one of my ViewModels that is an integer vs a collection.

    private int _formTypeID;
    public int FormTypeID
    {
        get { return _formTypeID; }

        set
        {
            if (_formTypeID == value)
            {
                return;
            }
            _formTypeID = value;
            RaisePropertyChanged("FormTypeID");
        }
    }

What I'd like to do is to load this from a query from my DomainContext. The query would look something like:

    public int GetFormTypeByForm(int Formid)
    {
        var p = (from i in this.ObjectContext.Forms
                where i.FormID == Formid
                select i.FormType).FirstOrDefault();

        return p;
    }

But I can't seem to figure out how to do this. I will be using this property for loading form specific data and also loading custom column definitions into my XAML.

Anyone know how to do this?

Thanks,

Neil

Answer 1

Do you have the parent form present in a collection? If yes your query should work, just use SingleOrDefault instead.

Otherwise, you have to load your form to the DomainContext:

private int _FormType;
public int FormType
{
  get { return _FormType; }
  set
  {
    if (_FormType == value) return;
    _FormType = value;
    RaisePropertyChanged("FormType");
  }
}

public void LoadFormTypeByForm(int Formid)
{
  var query = (from f in this.ObjectContext.Forms
               where f.FormID == Formid
               select f.FormType);

  var action = new Action<LoadOperation<Form>>((op) =>
    {
      if (op.HasError && !op.IsErrorHandled)
      {
        op.MarkErrorAsHandled();
        return;
      }
      var form = ObjectContext.Forms.SingleOrDefault(f => f.FormID == FormID);
      if (form != null)
        FormType = form.FormType;
    });
  Context.Load(query, action, null);
}