internal static Expression <Func <T, object> > GetOrderExpression <T>(ParsedOrdering order, IGridifyMapper <T> mapper)
{
var exp = mapper.GetExpression(order.MemberName);
switch (order.OrderingType)
{
case OrderingType.Normal:
return(exp);
case OrderingType.NullCheck:
case OrderingType.NotNullCheck:
default:
{
// member should be nullable
if (exp.Body is not UnaryExpression unary || Nullable.GetUnderlyingType(unary.Operand.Type) == null)
{
throw new GridifyOrderingException($"'{order.MemberName}' is not nullable type");
}
var prop = Expression.Property(exp.Parameters[0], order.MemberName);
var hasValue = Expression.PropertyOrField(prop, "HasValue");
switch (order.OrderingType)
{
case OrderingType.NullCheck:
{
var boxedExpression = Expression.Convert(hasValue, typeof(object));
return(Expression.Lambda <Func <T, object> >(boxedExpression, exp.Parameters));
}
case OrderingType.NotNullCheck:
{
var notHasValue = Expression.Not(hasValue);
var boxedExpression = Expression.Convert(notHasValue, typeof(object));
return(Expression.Lambda <Func <T, object> >(boxedExpression, exp.Parameters));
}
// should never reach here
case OrderingType.Normal:
return(exp);
default:
throw new ArgumentOutOfRangeException();
}
}
}
}
public static IEnumerable <Expression <Func <T, object> > > GetOrderingExpressions <T>(this IGridifyOrdering gridifyOrdering,
IGridifyMapper <T>?mapper = null)
{
if (string.IsNullOrWhiteSpace(gridifyOrdering.OrderBy))
{
throw new GridifyQueryException("OrderBy is not defined or not Found");
}
var members = ParseOrderings(gridifyOrdering.OrderBy !).Select(q => q.MemberName).ToList();
if (mapper is null)
{
foreach (var member in members)
{
Expression <Func <T, object> >?exp = null;
try
{
exp = GridifyMapper <T> .CreateExpression(member);
}
catch (Exception)
{
// skip if there is no mappings available
}
if (exp != null)
{
yield return(exp);
}
}
}
else
{
foreach (var member in members.Where(mapper.HasMap))
{
yield return(mapper.GetExpression(member) !);
}
}
}