How to enable filtering on an ObjectDataSource with FilterExpression when bound to a List<object>.

Does anyone know how to use FilterExpression with an ObjectDataSource when it is bound using a select method that returns a list of entity objects?

I get the following error when I attempt it:

"The data source 'testODS' only supports filtering when the SelectMethod returns a DataSet or a开发者_开发技巧 DataTable"

According to MSDN

The ObjectDataSource control supports filtering data only when the Select method returns a DataSet or DataTable object.

So if you want to filter your result set of entities, perhaps you can use a LinqDataSource instead.

<asp:LinqDataSource ID="LinqDataSource1" runat="server" 
    ContextTypeName="MyNamespace.MyDataContext" 

        Select="new (MyId, MyProperty1, MyCollection1.MyProperty2)" 
        TableName="MyTable" Where="MyProperty1.Contains(@PropertyFilter)" >
        <WhereParameters>
            <asp:ControlParameter ControlID="txtPropertyFilter" Name="PropertyFilter" 
                PropertyName="Text" Type="String" />
        </WhereParameters>
</asp:LinqDataSource>

Why not just do what the error says and use a DataTable or DataSet?

Convert generic list to dataset in C#

Use a select parameter for the ODS to hold the filter variable.

    <asp:ObjectDataSource ID="odsResults" runat="server" 
        OldValuesParameterFormatString="original_{0}" SelectMethod="GetSearchResults" 
        TypeName="LiftSearchResults" SortParameterName="sortType">
        <SelectParameters>
            <asp:Parameter Name="liftID" Type="Int32" />
            <asp:Parameter Name="sortType" Type="String" />
            <asp:Parameter Name="range" Type="Int32" />
        </SelectParameters>
    </asp:ObjectDataSource>

Data object method:

[DataObjectMethod(DataObjectMethodType.Select, false)]
    public List<SearchResultsLift>
        GetSearchResults(
        int liftID,
        string sortType,
        int range
        )
    {        
    List<SearchResultsLift> returnList =
        new List<SearchResultsLift>();

        ...Code to populate list...

        if (range != 0)
        returnList = FilterByRange(returnList, range);

        returnList = GetListSort(returnList, sortType);
    return returnList;
}

Unless the range parameter is explicitly set in the page it returns 0 and all records are returned. GetListSort (not shown) is a sort function.

private List<SearchResultsLift>
    FilterByRange(List<SearchResultsLift> filterList, int range)
{
    var fList = (from srl in filterList
                 where 
                 srl.DistanceFromDestination <= range &&
                 srl.DistanceFromStart <= range
                 select srl).ToList<SearchResultsLift>();
        return fList;
}
}