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user3235445
user3235445

Reputation: 155

WPF ComboBox SelectedItem when bound to an enum

I have a WPF ComboBox bound to a list of a class which contains an enum.

This all works fine, my question is at the end of this post, first the code:

Here is the class:

public class FILTER_TEST
{
    public FilterType Filter { get; private set; }
    public string Description { get; private set; }

    public static List<FILTER_TEST> CreateFilters()
    {
        var list = new List<FILTER_TEST>();

        list.Add(new FILTER_TEST() { Filter = FilterType.CheckNone, Description = "Uncheck all" });
        list.Add(new FILTER_TEST() { Filter = FilterType.CheckAll, Description = "Check all" });
        list.Add(new FILTER_TEST() { Filter = FilterType.CheckCustom, Description = "Custom check" });

        return list;
    }
}

Here is the enum FilterType:

public enum FilterType
{
    CheckNone,
    CheckAll,
    CheckCustom
}

In my view model I have the following:

public List<FILTER_TEST> FilterNames { get { return FILTER_TEST.CreateFilters(); } }

public FILTER_TEST SelectedFilter
{
    get { return selectedFilter; }
    set
    {
        if (value != selectedFilter)
        {
            selectedFilter = value;
            OnPropertyChanged("SelectedFilter");
        }
    }
}

Also in the view model, I set the SelectedItem of the ComboBox as follows:

SelectedFilter = FilterNames.Where(x => x.Filter == FilterType.CheckNone).FirstOrDefault();

Here is the xaml putting it all together:

<ComboBox DisplayMemberPath="Description" ItemsSource="{Binding FilterNames}"
SelectedItem="{Binding SelectedFilter, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" IsSynchronizedWithCurrentItem="True"/>

My problem is that although the changing of the SelectionItem works, the actual value displayed in the ComboBox doesn’t change.

The initial SelectedItem is “Uncheck all” as, when the window has been loaded, none of the corresponding CheckBox controls (bound to another class which contains a Boolean property) have been checked. What I would like is that when a CheckBox has been checked, then the SelectedItem changes to “Custom check”.

This does indeed change the value of the SelectedItem:

SelectedFilter = FilterNames.Where(x => x.Filter == FilterType.CheckCustom).FirstOrDefault();

But the text shown in the ComboBox is still “Uncheck all”.

Does anyone have an idea as to what I am missing? I am forced to use the 4.0 framework, I don’t know if this is relevant.

Upvotes: 1

Views: 610

Answers (1)

rdoubleui
rdoubleui

Reputation: 3598

I've seen the hint to overwrite Equals() of the type in use as this:

public override bool Equals(object o)
{
      if (o is FILTER_TEST)
      {
           var other = o as FILTER_TEST;
           return this.Description == other.Description && this.Filter == other.Filter;
      }
      else
           return false;
}

Now that makes your sample work. Let me come back for a reference on the why.

Upvotes: 1

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