QueryableFilterUserControl.GetQueryable Method (IQueryable)

.NET Framework (current version)
 

Gets the transformed IQueryable object from the source IQueryable object.

Namespace:   System.Web.DynamicData
Assembly:  System.Web.DynamicData (in System.Web.DynamicData.dll)

Public MustOverride Function GetQueryable (
	source As IQueryable
) As IQueryable

Parameters

source
Type: System.Linq.IQueryable

The source IQueryable object.

Return Value

Type: System.Linq.IQueryable

The transformed IQueryable object from the source IQueryable object.

You must implement this method if you derive a control from QueryableFilterUserControl.

This method is implemented to transform the source IQueryable object into the target IQueryable object. Examples of IQueryable expressions that you might want to implement include order by, range, or search.

The following example shows how to implement the GetQueryable method for a Boolean filter that is derived from QueryableFilterUserControl.

Public Overloads Overrides Function GetQueryable(ByVal source As IQueryable) As IQueryable 
    If [String].IsNullOrEmpty(DropDownList1.SelectedValue) Then 
        Return source 
    End If 

    Dim value As Boolean = Convert.ToBoolean(DropDownList1.SelectedValue) 

    Dim parameterExpression As ParameterExpression = Expression.Parameter(source.ElementType, "item") 
    Dim body As Expression = BuildQueryBody(parameterExpression, value) 

    Dim lambda As LambdaExpression = Expression.Lambda(body, parameterExpression) 
    Dim whereCall As MethodCallExpression = Expression.[Call](GetType(Queryable), "Where", _
         New Type() {source.ElementType}, source.Expression, Expression.Quote(lambda)) 
    Return source.Provider.CreateQuery(whereCall) 
End Function

.NET Framework
Available since 4.0
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