how create predicate from grid filters

[tuan]

hi!,

In silverlight, how can i create predicate from grid filters. ( I can FilterDescriptors)
 
I read http://www.telerik.com/community/forums/silverlight/gridview/lamba-predicate-from-grid-filters.aspx but I can not it

public static IQueryable Where(this IQueryable source, IEnumerable<IFilterDescriptor> filterDescriptors)
        {
            if (filterDescriptors.Count() > 0)
            {
                var parameterExpression = Expression.Parameter(source.ElementType, "item");

                var expressionBuilder = new FilterDescriptorCollectionExpressionBuilder(parameterExpression, filterDescriptors);
                var predicate = expressionBuilder.CreateFilterExpression();
                return source.Where(predicate);
            }

            return source;
        }

but FilterDescriptorCollectionExpressionBuilder unavailable in silverlight.