public static Expression NullCheckSource(ProfileMap profileMap, Expression sourceParameter, Expression destinationParameter, Expression mapExpression, MemberMap memberMap)
{
var sourceType = sourceParameter.Type;
if (sourceType.IsValueType && !sourceType.IsNullableType())
{
return(mapExpression);
}
var destinationType = destinationParameter.Type;
var isCollection = destinationType.IsCollection();
var mustUseDestination = memberMap is { MustUseDestination : true };
var ifSourceNull = memberMap == null?
destinationParameter.IfNullElse(DefaultDestination(), ClearDestinationCollection()) :
mustUseDestination?ClearDestinationCollection() : DefaultDestination();
return(sourceParameter.IfNullElse(ifSourceNull, mapExpression));
Expression ClearDestinationCollection()
{
if (!isCollection)
{
return(destinationParameter);
}
MethodInfo clearMethod;
var destinationVariable = Variable(destinationParameter.Type, "collectionDestination");
Expression collection = destinationVariable;
if (destinationType.IsListType())
{
clearMethod = IListClear;
}
else
{
var destinationCollectionType = destinationType.GetICollectionType();
if (destinationCollectionType == null)
{
if (!mustUseDestination)
{
return(destinationParameter);
}
var destinationElementType = GetEnumerableElementType(destinationType);
destinationCollectionType = typeof(ICollection <>).MakeGenericType(destinationElementType);
collection = Convert(collection, destinationCollectionType);
}
clearMethod = destinationCollectionType.GetMethod("Clear");
}
return(Block(new[] { destinationVariable },
Assign(destinationVariable, destinationParameter),
Condition(ReferenceEqual(destinationVariable, Null), Empty, Expression.Call(collection, clearMethod)),
destinationVariable));
}
Expression DefaultDestination()
{
if ((isCollection && profileMap.AllowsNullCollectionsFor(memberMap)) || (!isCollection && profileMap.AllowsNullDestinationValuesFor(memberMap)))
{
return(destinationParameter.NodeType == ExpressionType.Default ? destinationParameter : Default(destinationType));
}
if (destinationType.IsArray)
{
var destinationElementType = destinationType.GetElementType();
var rank = destinationType.GetArrayRank();
return(rank == 1 ?
Expression.Call(ArrayEmptyMethod.MakeGenericMethod(destinationElementType)) :
NewArrayBounds(destinationElementType, Enumerable.Repeat(Zero, rank)));
}
return(ObjectFactory.GenerateConstructorExpression(destinationType));
}
}
