public static Conversion GetExplicit(Operand op, Type to, bool onlyStandard)
{
// try implicit
Conversion conv = GetImplicit(op, to, onlyStandard);
if (conv.IsValid)
{
return(conv);
}
Type from = Operand.GetType(op);
// section 6.3.2 - Standard explicit conversions
if (onlyStandard)
{
if (from == null || !GetImplicit(to, from, true).IsValid)
{
return(Invalid.Instance);
}
}
TypeCode tcFrom = Type.GetTypeCode(from);
TypeCode tcTo = Type.GetTypeCode(to);
byte ct = convTable[(int)tcFrom][(int)tcTo];
// section 6.2.1 - Explicit numeric conversions, 6.2.2 - Explicit enumeration conversions
if ((from.IsPrimitive || from.IsEnum || from == typeof(decimal)) && (to.IsPrimitive || to.IsEnum || to == typeof(decimal)))
{
if (ct == D)
{
return(Direct.Instance); // this can happen for conversions involving enum-s
}
if (ct <= E)
{
if (from == typeof(decimal) || to == typeof(decimal))
{
// decimal is handled as user-defined conversion, but as it is a standard one, always enable UDC processing
onlyStandard = false;
}
else
{
return(Primitive.Instance);
}
}
}
// section 6.2.5 - User-defined explicit conversions (details in section 6.4.4)
if (!(onlyStandard || from == typeof(object) || to == typeof(object) || from.IsInterface || to.IsInterface ||
to.IsSubclassOf(from) || from.IsSubclassOf(to)))
{
List <UserDefined> candidates = null;
FindCandidates(ref candidates, FindExplicitMethods(from, to), op, to, GetExplicit);
if (candidates != null)
{
if (candidates.Count == 1)
{
return(candidates[0]);
}
return(UserDefined.FindExplicit(candidates, from, to));
}
}
// section 6.2.3 - Explicit reference conversions, 6.2.4 - Unboxing conversions
// TODO: not really according to spec, but mostly works
if (!from.IsValueType && from.IsAssignableFrom(to))
{
if (to.IsValueType)
{
return(Unboxing.Instance);
}
else
{
return(Cast.Instance);
}
}
return(Invalid.Instance);
}