Question

I have an Entity result of List<string> GetTagsData that I need to somehow bind with checkboxes in an ObservableCollection and then to a DataGrid. These checkbox bindings correspond to a dynamic comma delimited string that is a subset of that entity result GetTagsData except it’s in a comma delimited string. The user then can uncheck or check each item in the DataGrid and then we call an event handler to basically regenerate the comma delimited string. My question is this, Is there a better way of architecting this solution? I see this as potential problematic to maintain in the future. the only thing that I can’t change is the comma delimited string coming in and out. and I have to build it in silverlight. Thanks ahead!

Comma Delimited String

'Chicago','New York','Boston','Los Angeles'

Entity Result for List<string> GetTagsData

GetTagsData = SecurityDomainContext.Current.vwBusinessUnits.Select(d => d.Market).Distinct().ToList();

ObservableCollection Class

    public class TagsCollection : ViewModelBase 
{
    private string _tag;   
    private bool _isSelected; 
    public string Tag
    {
        get
        { return _tag; }
        set 
        { _tag = value; }
    }

    public bool IsSelected
    {
        get 
        { return _isSelected; }
        set 
        { _isSelected = value; }
    }  

Now in my ViewModel I am able to iterate the Entity results into the Collection and bind that Collection to the DataGrid.

private ObservableCollection<TagsCollection> GetTagsCollection(string colName)
        {
            ObservableCollection<TagsCollection> ocTags = new ObservableCollection<TagsCollection>();

                            foreach (string tag in GetTagsData)
                        {
                            if (DelimitedTagSet.Contains(tag.Trim()))
                            {
                                ocTags.Add(new TagsCollection { Tag = tag, IsSelected = true });
                            }
                            else
                            {
                                ocTags.Add(new TagsCollection { Tag = tag, IsSelected = false });
                            }                               
                        }
            return ocTags;
        }

Here’s what the xaml view looks like

Answer 1

Based on my understanding, the states you have to provide is a dynamic immutable list of options where you want to prompt user to enable/disable each of them, then return result as original string.

If the list is a static list that you expect, for instance states, I’d surely suggest you having a list of states, and mapping against it.

Make an Tag class that implement INotifyPropertyChanged, that has two props (name, selected) and remember to raise the PropertyChanged for each property change (I see it’s excluded from your code, I assume for brevity purposes).

Make a List subclass, add a string constructor and override the ToString(), make all the parsing in this class and return the result on the ToString, then call it from you ViewModel.

I now realize that you tagged the question with , so why would you want to bind against that comma delimited string?

You might want to expose the options in the server and treat it like this, so the client doesn’t know it’s a comma delimited.

public class OptionsViewModel : ViewModelBase
{

  public OptionsViewModel()
  {
     IsBusy = True;
     var context = new MyDomainContext();
     _Tags = context.Tags;
     //if called elsewhere but from ctor, make sure context.IsLoading is false;
     //The Load method is throwing an exception if re-loading when a load is on.
     //Debug.Assert(!context.IsLoading);
     context.Load(
        context.GetTagsQuery(),
        (op) =>
        {
          if(op.HasError && !op.IsErrorHandled) op.MarkErrorAsHandlere();
          IsBusy = false;
        },
        null);
  }

  private readonly Ienumerable<Tag> _Tags;
  public Ienumerable<Tag> Tags
  {
    get
    {
      return _Tags;
    }
  }

}

In the server expose an operation that returns that datacontract (of Tag) and the server should do the comma string parsing.