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Filtering Overview

RadListView for ASP.NET AJAX features integrated filtering capabilities. Filtering is achieved through the definition of filter expressions which should consequently be added to the FilterExpressions collection of the control.

Each filter function has a corresponding type that should be used for the construction of the filter expression. If, for example, a filter expression with a GreaterThan logical operator is to be defined, the RadListViewGreaterThanFilterExpression type is there to help you build the expression. The same goes for all the other filter operators (functions).

Building filter expressions

The filter expressions can be added to RadListView's FilterExpressions collection in several ways:

  • Creating instances of the new filter expressions and adding them to the FilterExpressions collection.

          RadListView1.FilterExpressions.Add( new RadListViewGreaterThanFilterExpression<DateTime>("ShippedDate"){CurrentValue
          = DateTime.Parse("7/10/1996")} ); RadListView1.FilterExpressions.Add( new RadListViewEqualToFilterExpression<int>("OrderID"){CurrentValue
          = 42} );
  • Using the fluent expression builder object which can be used to build the expressions in a more stream-lined manner. With this approach you need to remember to call the Build() method upon the expression once it is declared.

          RadListView1.FilterExpressions.BuildExpression() .GreaterThan("ShippedDate",
          DateTime.Parse("7/10/1996")) .Or().EqualTo("OrderID", 42).Build();
  • The last and most consise way is provided by an overload of the FilterExpressions collection BuildExpression method which takes in as an argument an Action delegate.

          RadListView1.FilterExpressions.BuildExpression(expression => expression .GreaterThan("ShippedDate",
          DateTime.Parse("7/10/1996")) .Or().EqualTo("OrderID", 42) ) );

More information on the APIs used for these ways of filtering and some code samples can be found here.

Grouping the filter expressions

One of RadListView's most powerful filtering features is the easy way to tie several filter expressions into one group and treat it as a single expression that can participate in further logical operations. Again a dedicated type is provided out-of-the-box to help you in this regard - the RadListViewGroupFilterExpression. It can be used in all of the above ways to construct filter expressions and add them to the FilterExpressions collection of the RadListView control. The sample filter expressions above can be extended with the group feature as follows:

      RadListView1.FilterExpressions .BuildExpression(expression => expression .GreaterThan("ShippedDate",
      DateTime.Parse("7/10/1996")) .Or().EqualTo("OrderID", 42) .And().Group(group =>
      group.IsNotEmpty("ShipCountry") .And().Contains("ShipCountry", "G") ) );

Again further information can be found here.

Filtering with RadFilter

The above functionalities can also be achieved without manually building the filter expression. RadFilter control which provides UI and back-end for building complex filtering criteria. In most cases it is enough to assign the ID of RadListView to the FilteredControlID property of the RadFilter and you are ready to go. This is demonstrated in the following online demo:

ListView / Filtering with RadFilter

For more custom scenarios (like applying expressions on custom actions, building expressions through the filter APIs, etc.) the FireApplyCommand() method along with the OnApplyExpressions event are used. RadFilter has a query provider written to produce filter queries specifically for the RadListView control - RadFilterListViewQueryProvider. You can use it to extract the built custom expression and assign it to RadListView. You can see a code sample on using the provider in the following help article:

RadListView Filtering with RadFilter

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