private static FilterSpecification <T> CombineSpecification(FilterSpecification <T> left, FilterSpecification <T> right, Func <Expression, Expression, BinaryExpression> combiner)
{
var expr1 = left.SpecificationExpression;
var expr2 = right.SpecificationExpression;
var arg = Expression.Parameter(typeof(T));
var combined = combiner.Invoke(
new ReplaceParameterVisitor {
{ expr1.Parameters.Single(), arg }
}.Visit(expr1.Body),
new ReplaceParameterVisitor {
{ expr2.Parameters.Single(), arg }
}.Visit(expr2.Body));
return(new ConstructedSpecification <T>(Expression.Lambda <Func <T, bool> >(combined, arg)));
}
public FilterSpecification <T> Or(FilterSpecification <T> other)
{
return(this | other);
}
public FilterSpecification <T> And(FilterSpecification <T> other)
{
return(this & other);
}
public static FilterSpecification <TDerived> ConvertSpecification <TBase, TDerived>(FilterSpecification <TBase> original) where TDerived : TBase
{
var expr1 = original.SpecificationExpression;
var arg = Expression.Parameter(typeof(TDerived));
var newBody = new ReplaceParameterVisitor {
{ expr1.Parameters.Single(), arg }
}.Visit(expr1.Body);
return(new ConvertedSpecification <TDerived>(Expression.Lambda <Func <TDerived, bool> >(newBody, arg)));
}