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Persisting a custom filter

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GridView

This is a migrated thread and some comments may be shown as answers.

7 Answers, 1 is accepted

answered on 15 Nov 2012, 09:17 AM

CustomColumnFilterDescriptor.zip

Hello,

What you can try to do is to create your custom column filter descriptor that inherist from our stock one.

Then you need to override the CreateFilterExpression and return an expression that will be used by our data engine for filtering. You will build this custom expression based on what the user has entered in the UI, i.e. you will be reading stuff from:

((IColumnFilterDescriptor)this).DistinctFilter and ((IColumnFilterDescriptor)this).FieldFilter.

Take a careful look at the ICoumnFilterDescriptor interface - it is a direct representation of the filtering UI. More about this you can learn from here. Please read this before going on.

Once you have gathered the data you only need to build your LINQ expression and return it to our data engine.

I have attached a sample project that builds a custom column filter descriptor for a flags enum type, but the idea and the approach should be the same in your case. You can debug this project to see what is going on and then tailor the custom column filter descriptor to your particular needs, i.e. return a LINQ Expression that will filter your collection property.

I hope this helps.

Regards,
Rossen Hristov
the Telerik team

Explore the entire Telerik portfolio by downloading Telerik DevCraft Ultimate.

answered on 15 Nov 2012, 05:23 PM

I've made my filter inherit from a stock one. This is what it looks like:

public sealed class CollectionFilterDescriptor : MemberColumnFilterDescriptor

{

private static readonly MethodInfo EnumerableCastMethod = typeof(Enumerable).GetMethod("Cast");

private static readonly MethodInfo GenericContainsMethod = GetGenericContainsMethodInfo();

private static MethodInfo GetGenericContainsMethodInfo()

{

var methodCall = ((MethodCallExpression)((Expression<Func<IEnumerable<object>, bool>>)

(source => source.Contains(null))).Body).Method.GetGenericMethodDefinition();

return methodCall.MakeGenericMethod(typeof(object));

}

private readonly GridViewBoundColumnBase column;

public CollectionFilterDescriptor(GridViewBoundColumnBase column)

: base(column)

{

this.column = column;

}

public override Expression CreateFilterExpression(Expression instance)

{

var propertyName = this.column.DataMemberBinding.Path.Path;

var collectionPropertyAccessor = Expression.Property(instance, propertyName);

var genericCollectionPropertyAccessor = Expression.Call(

null, EnumerableCastMethod.MakeGenericMethod(new[] { typeof(object) }), collectionPropertyAccessor);

var value = ((IColumnFilterDescriptor)this).DistinctFilter.DistinctValues.First();

Expression result = Expression.Call(

GenericContainsMethod, genericCollectionPropertyAccessor, Expression.Constant(value));

return result;

}

I'm using this filter to filter a collection of strings based on the string typed into my little filter.

I try to restore this filter using code as such:

private static void RestoreFilterDescriptors(IEnumerable<FilterSetting> filterSettings, RadGridView gridView)

{

gridView.FilterDescriptors.SuspendNotifications();

foreach (var c in gridView.Columns)

{

if (c.ColumnFilterDescriptor.IsActive) c.ClearFilters();

}

foreach (var setting in filterSettings)

{

var column = gridView.Columns[setting.ColumnUniqueName];

var columnFilter = column.ColumnFilterDescriptor;

foreach (var distinctValue in setting.SelectedDistinctValues)

{

columnFilter.DistinctFilter.AddDistinctValue(distinctValue);

}

if (setting.Filter1 != null)

{

columnFilter.FieldFilter.Filter1.Operator = setting.Filter1.Operator;

columnFilter.FieldFilter.Filter1.Value = setting.Filter1.Value;

columnFilter.FieldFilter.Filter1.IsCaseSensitive = setting.Filter1.IsCaseSensitive;

}

columnFilter.FieldFilter.LogicalOperator = setting.FieldFilterLogicalOperator;

if (setting.Filter2 != null)

{

columnFilter.FieldFilter.Filter2.Operator = setting.Filter2.Operator;

columnFilter.FieldFilter.Filter2.Value = setting.Filter2.Value;

columnFilter.FieldFilter.Filter2.IsCaseSensitive = setting.Filter2.IsCaseSensitive;

}

gridView.FilterDescriptors.ResumeNotifications();

}

Unfortunately, I get one of two errors depending on when I try to do this.

Error 1
Error: The value "Telerik.Windows.Controls.GridView.MemberColumnFilterDescriptor" is not of type
Stack Trace:

at System.ThrowHelper.ThrowWrongValueTypeArgumentException(Object value, Type targetType)

at System.Collections.ObjectModel.Collection`1.System.Collections.IList.Add(Object value)

at Telerik.Windows.Data.CollectionHelper.Equalize(IList left, IList right, IEqualityComparer comparer)

at Telerik.Windows.Data.CollectionHelper.Equalize(IList left, IList right)

at Telerik.Windows.Data.DataItemCollection.EqualizeFilterDescriptors()

at Telerik.Windows.Data.DataItemCollection.EqualizeDescriptors()

at Telerik.Windows.Data.DataItemCollection.set_CollectionView(QueryableCollectionView value)

at Telerik.Windows.Data.DataItemCollection.CreateAndSetCollectionView(IEnumerable source, Type itemType)

at Telerik.Windows.Data.DataItemCollection.SetItemsSource(IEnumerable source, Type itemType)

at Telerik.Windows.Controls.GridView.GridViewDataControl.<>c__DisplayClass14.<Bind>b__13()

at Telerik.Windows.Controls.CursorManager.PerformTimeConsumingOperation(FrameworkElement frameworkElement, Action action)

at Telerik.Windows.Controls.GridView.GridViewDataControl.Bind(Object newValue)

at Telerik.Windows.Controls.GridView.GridViewDataControl.OnApplyTemplate()

at System.Windows.FrameworkElement.ApplyTemplate()

at System.Windows.FrameworkElement.MeasureCore(Size availableSize)