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QueryableFilterUserControl.GetQueryable Method

Gets the transformed IQueryable object from the source IQueryable object.

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

public abstract IQueryable GetQueryable(
	IQueryable source
)

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 override IQueryable GetQueryable(IQueryable source) {
    if (String.IsNullOrEmpty(DropDownList1.SelectedValue)) {
        return source;
    }

    bool value = Convert.ToBoolean(DropDownList1.SelectedValue);

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

    LambdaExpression lambda = Expression.Lambda(body, 
        parameterExpression);
    MethodCallExpression whereCall = Expression.Call(
        typeof(Queryable), 
        "Where", 
        new Type[] { source.ElementType }, 
        source.Expression, Expression.Quote(lambda));
    return source.Provider.CreateQuery(whereCall);
}

.NET Framework

Supported in: 4.6, 4.5, 4
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