/// <summary>
/// Creates a predicate filter expression combining <see cref="FilterDescriptors"/>
/// expressions with <see cref="LogicalOperator"/>.
/// </summary>
/// <param name="parameterExpression">The parameter expression, which will be used for filtering.</param>
/// <returns>A predicate filter expression.</returns>
protected override Expression CreateFilterExpression(ParameterExpression parameterExpression)
{
var builder = new FilterDescriptorCollectionExpressionBuilder(parameterExpression, this.FilterDescriptors, this.LogicalOperator);
builder.Options.CopyFrom(this.ExpressionBuilderOptions);
return builder.CreateBodyExpression();
}
/// <summary>
/// Filters a sequence of values based on a collection of <see cref="IFilterDescriptor"/>.
/// </summary>
/// <param name="source">The source.</param>
/// <param name="filterDescriptors">The filter descriptors.</param>
/// <returns>
/// An <see cref="IQueryable" /> that contains elements from the input sequence
/// that satisfy the conditions specified by each filter descriptor in <paramref name="filterDescriptors" />.
/// </returns>
public static IQueryable Where(this IQueryable source, IEnumerable<IFilterDescriptor> filterDescriptors)
{
if (filterDescriptors.Any())
{
var parameterExpression = Expression.Parameter(source.ElementType, "item");
var expressionBuilder = new FilterDescriptorCollectionExpressionBuilder(parameterExpression, filterDescriptors);
expressionBuilder.Options.LiftMemberAccessToNull = source.Provider.IsLinqToObjectsProvider();
var predicate = expressionBuilder.CreateFilterExpression();
return source.Where(predicate);
}
return source;
}
