In WPF, displaying only empty fields

Question

In WPF, I have a ListView which is bounded to a Dictionary (InpLangList) and a CheckBox bounded with a boolean(IsShowEmptyFields) property.

Eg. private Dictionary<string, string> _langList = new Dictionary<string, string>();

<ListView ItemsSource="{Binding InpLangList, Mode=TwoWay}" >
    <ListView.View>
        <GridView>
            <GridViewColumn Header="Id" Width="Auto" DisplayMemberBinding="{Binding Key}" />
            <GridViewColumn Header="Values" Width="Auto" DisplayMemberBinding="{Binding Value}" />
        </GridView>
    </ListView.View>
</ListView>

public Dictionary<string, string> InpLangList
{
    get { return _langList ; }
    set
    {
        _langList = value; 
        NotifyPropertyChanged();
    }
}

(...)

InpLangList.Add("id1","One");
InpLangList.Add("id2","");
InpLangList.Add("id3","");
InpLangList.Add("id4","Four");
InpLangList.Add("id5","Five");

(...)

private bool _isShowEmptyFields;

public bool IsShowEmptyFields
{
    get { return _isShowEmptyFields; }
    set
    {
        _isShowEmptyFields = value; 
        NotifyPropertyChanged();
    }
}

What I need is, if Checkbox is checked, then I want to display only the empty fields, i.e.

InpLangList.Add("id2","");
InpLangList.Add("id3","");

should be displayed in the ListView else entire InpLangList should be displayed in the ListView.

Answer 1

Use CollectionView:

ViewModel:

// Actual data source
Dictionary<string, string> inpLangList = new Dictionary<string, string>();
// A presentation of your data that you can group, sort, filter, etc
public ICollectionView InpLangList { get; set; }

private bool _isShowEmptyFields;
public bool IsShowEmptyFields 
{
    get { return _isShowEmptyFields; }
    set 
    {
        _isShowEmptyFields = value;
        // if the presentation of your data is assigned - filter it
        InpLangList?.Refresh();
    }
}

// ViewModel constructor
public VM()
{
    inpLangList.Add("id1", "One");
    inpLangList.Add("id2", "");
    inpLangList.Add("id3", "");
    inpLangList.Add("id4", "Four");
    inpLangList.Add("id5", "Five");
    // note what's going next:
    // assigning the data source to it's presentation (view)
    InpLangList = CollectionViewSource.GetDefaultView(inpLangList);
    // assigning filter that will be applied to your data source
    // before the showing it within the UI
    InpLangList.Filter = (obj) => 
    {
        if (!(obj is KeyValuePair<string, string> pair))
            return false;
         return !IsShowEmptyFields || string.IsNullOrEmpty(pair.Value);
    };
}

View:

<CheckBox IsChecked="{Binding IsShowEmptyFields}" Content="Empty only"/>
<ListView ItemsSource="{Binding InpLangList}" >
    <ListView.View>
         <GridView>
            <GridViewColumn Header="Id" Width="Auto" DisplayMemberBinding="{Binding Key}" />
            <GridViewColumn Header="Values" Width="Auto" DisplayMemberBinding="{Binding Value}" />
        </GridView>
    </ListView.View>
</ListView>