/// <summary>
/// Produces the Linq expression representing the entire filter descriptors collection.
/// </summary>
/// <param name="filterDescriptors">Collection of filters</param>
/// <param name="filterOperator">The operator used to combine filters</param>
/// <param name="expressionCache">Cache for storing built expressions</param>
/// <returns>Produced linq expression, which can be <c>null</c> if there are no filter descriptors.</returns>
public static Expression BuildFiltersExpression(
FilterDescriptorCollection filterDescriptors,
FilterDescriptorLogicalOperator filterOperator,
ExpressionCache expressionCache)
{
Debug.Assert(filterDescriptors != null, "Unexpected null filterDescriptors");
Expression filtersExpression = null;
foreach (FilterDescriptor filterDescriptor in filterDescriptors)
{
// Ignored filters will not have a cache entry
if (expressionCache.ContainsKey(filterDescriptor))
{
Expression filterExpression = expressionCache[filterDescriptor];
if (filtersExpression == null)
{
filtersExpression = filterExpression;
}
else if (filterOperator == FilterDescriptorLogicalOperator.And)
{
filtersExpression = Expression.AndAlso(filtersExpression, filterExpression);
}
else
{
filtersExpression = Expression.OrElse(filtersExpression, filterExpression);
}
}
}
return(filtersExpression);
}
/// <summary>
/// Initializes a new instance of the <see cref="FilterCollectionManager"/> class.
/// </summary>
/// <param name="sourceCollection">The collection of <see cref="FilterDescriptor"/>s to manage</param>
/// <param name="expressionCache">The cache with entries for the <see cref="FilterDescriptor"/>s</param>
/// <param name="validationAction">The callback for validating items that are added or changed</param>
public FilterCollectionManager(FilterDescriptorCollection sourceCollection, ExpressionCache expressionCache, Action <FilterDescriptor> validationAction)
{
if (sourceCollection == null)
{
throw new ArgumentNullException("sourceCollection");
}
if (expressionCache == null)
{
throw new ArgumentNullException("expressionCache");
}
if (validationAction == null)
{
throw new ArgumentNullException("validationAction");
}
this.ExpressionCache = expressionCache;
this._sourceCollection = sourceCollection;
this.ValidationAction = (item) => validationAction((FilterDescriptor)item);
this.AsINotifyPropertyChangedFunc = (item) => ((FilterDescriptor)item).Notifier;
this.AddCollection(this._sourceCollection);
}