Trying to create custom filter for RadGridView

[Mark]

I'm trying to create a custom filter for a RadGridView, but no matter what I do I get the following error.

 

The value "(CategoryList Contains Allergies)" is not of type "Telerik.Windows.Data.IFilterDescriptor" and cannot be used in this generic collection.
Parameter name: value

 

The column that the filter is on contains a List<string> of possibly multiple category names in each row and the filter contains a distinct list of the categories.

 

001.public partial class CategoryFilter : UserControl, IFilteringControl
002.{
003.    private GridViewBoundColumnBase _column;
004.
005.    public delegate void BeginCategoryChangeEvent();
006.    public event BeginCategoryChangeEvent BeginCategoryChange;
007.
008.    public delegate void CategoryChangeEvent();
009.    public event CategoryChangeEvent CategoryChange;
010.    private CompositeFilterDescriptor _compositeFilter;
011.
012.
013.    public class CategoryItem
014.    {
015.        public string CategoryName { get; set; }
016.        public bool IsChecked { get; set; }
017.    }
018.
019.    private List<CategoryItem> MainCategoryList;
020.
021.    /// <summary>
022.    /// Gets or sets a value indicating whether the filtering is active.
023.    /// </summary>
024.    public bool IsActive
025.    {
026.        get { return (bool)GetValue(IsActiveProperty); }
027.        set { SetValue(IsActiveProperty, value); }
028.    }
029.
030.    /// <summary>
031.    /// Identifies the <see cref="IsActive"/> dependency property.
032.    /// </summary>
033.    public static readonly DependencyProperty IsActiveProperty =
034.        DependencyProperty.Register(
035.            "IsActive",
036.            typeof(bool),
037.            typeof(CategoryFilter),
038.            new System.Windows.PropertyMetadata(false));
039.
040.
041.
042.
043.    public bool this[string CategoryName]
044.    {
045.        get
046.        {
047.            CategoryItem item = MainCategoryList.FirstOrDefault(i => i.CategoryName == CategoryName);
048.
049.            if (item == null)
050.                throw new Exception("Category Name not found");
051.
052.            return (item.IsChecked);
053.        }
054.        set
055.        {
056.            CategoryItem item = MainCategoryList.FirstOrDefault(i => i.CategoryName == CategoryName);
057.
058.            if (item == null)
059.                throw new Exception("Category Name not found");
060.
061.            item.IsChecked = value;
062.        }
063.    }
064.
065.    [TypeConverter(typeof(String))]
066.    public List<string> Categories
067.    {
068.        get
069.        {
070.            return MainCategoryList.Where(i => i.IsChecked).Select(i => i.CategoryName).ToList();
071.        }
072.        set
073.        {
074.            foreach (CategoryItem item in MainCategoryList)
075.            {
076.                item.IsChecked = value.Contains(item.CategoryName);
077.            }
078.        }
079.    }
080.
081.    public System.Windows.Controls.ListBox CategoryList
082.    {
083.        get { return this.LstCategories; }
084.    }
085.
086.    public CategoryFilter()
087.    {
088.        InitializeComponent();
089.    }
090.
091.    public void Prepare(GridViewColumn column)
092.    {
093.        this._column = column as GridViewBoundColumnBase;
094.        if (this._column == null)
095.        {
096.            return;
097.        }
098.
099.        List<string> catList = ((List<EducationChoices>)(column.DataControl.ItemsSource))
100.            .SelectMany(l => l.CategoryList)
101.            .Distinct()
102.            .Where(l => (l ?? "")
103.                .Trim() != "")
104.            .OrderBy(c => c)
105.            .ToList();
106.
107.        MainCategoryList = catList
108.                .Select(i => new CategoryItem() {CategoryName = i, IsChecked = false})
109.                .ToList();
110.
111.        LstCategories.ItemsSource = MainCategoryList;
112.    }
113.
114.    private void ChangeFilter(object sender, RoutedEventArgs e) {
115.        BeginCategoryChange();
116.
117.        if (_compositeFilter != null) {
118.            _column.DataControl.FilterDescriptors.Remove(_compositeFilter);
119.        }
120.        _compositeFilter = new CompositeFilterDescriptor { LogicalOperator = FilterCompositionLogicalOperator.Or };
121.        var dataMember = _column.DataMemberBinding.Path.Path;
122.
123.        string Category = ((CheckBox)e.OriginalSource).Tag.ToString();
124.
125.        foreach (var item in MainCategoryList) {
126.            if (item.IsChecked) {
127.                var filter = new FilterDescriptor(dataMember, FilterOperator.Contains, Category);
128.                _compositeFilter.FilterDescriptors.Add(filter);
129.            }
130.        }
131.
132.        if ((((CheckBox)e.OriginalSource).IsChecked ?? false) &&
133.                    _compositeFilter.FilterDescriptors.All(f => ((FilterDescriptor)f).Value.ToString() != Category))
134.        {
135.            var filter = new FilterDescriptor(dataMember, FilterOperator.Contains, Category);
136.            _compositeFilter.FilterDescriptors.Add(filter);
137.        } else if (!(((CheckBox) e.OriginalSource).IsChecked ?? false) &&
138.                   _compositeFilter.FilterDescriptors.Any(f => ((FilterDescriptor) f).Value.ToString() == Category))
139.        {
140.            _compositeFilter.FilterDescriptors.Remove(
141.                _compositeFilter.FilterDescriptors.FirstOrDefault(
142.                    f => ((FilterDescriptor) f).Value.ToString() == Category));
143.        }
144.
145.
146.        if (!_column.DataControl.FilterDescriptors.Contains(_compositeFilter)) {
147.            _column.DataControl.FilterDescriptors.Add(_compositeFilter);
148.        }
149.
150.        this.IsActive = true;
151.
152.        CategoryChange();
153.    }
154.}

 

I found this thread and tried to figure out what it was doing, but it didn't help.

[Mark]

I forgot to mention that the error keeps showing up on line 147, above.

_column.DataControl.FilterDescriptors.Add(_compositeFilter);

[Dilyan Traykov]

Hello Mark,

This exception is normally thrown when an element which is not an IFIlterDescriptor is added to the FilterDescriptors collection. But I'm afraid I'm unable to reproduce it on my end.
Can you please have a look at the Custom Filtering Controls article of the RadGridView documentation, as the recommended approach for creating a Custom FilteringControl is demonstrated in it?
Please also observe the Custom Filter Control demo from our SDK examples browser.

Regards,
Dilyan Traykov
Telerik