Hi, I have been using version 1.1. In that version, class SD.LLBLGen.Pro.ORMSupportClasses.DataAccessAdapterBase had a property named TypeDefaultValueSupplier. There is no such property in V3, and I was wondering what can be used instead of this, or what should be done to achieve this functionality?

Can you give us an example of what you need to achieve with this ? This may help us point you in the right direction.

Thanks

Matt

I need to somehow tell my data access component which values should be default for which type, that is, I need to tell which values should be saved to database as NULL values, and vice versa. For example, when I have property that is type of long, if it's value is -1, I want it to be saved as NULL. When I read it from the database, I want the NULL value to be mapped as -1.

Thanks

There is a class called TypeDefaultValue generated into the HelperClasses folder of the generated project. This class decides the return value of each type.

Thank you for the answer, but can you tell me how to use that class in order to achieve mentioned functionallity?

In the databasegeneric project, helper classes, the class TypeDefaultValue is the one which provides default values for NULL valued properties. This works for reads.

It's highly discouraged to use magic values for null. If you don't want to set a field, simply don't set it to a value. So if a field of type int has to be null as you didn't set it to a valid value, simply don't set it to any value, NULL will be inserted for that field.

Ok, but what if I have value "5" in database for some int field, and I want it to be NULL again? I would have to read it, create an object from that row, and change the value for mapped property to a value that would be saved as NULL. How can I do this?

There is method

ITypeDefaultValue CreateTypeDefaultValueProvider()

on EntityBase2 which should be overridden. I suppose that's the way to do this...

Dja wrote:

Ok, but what if I have value "5" in database for some int field, and I want it to be NULL again? I would have to read it, create an object from that row, and change the value for mapped property to a value that would be saved as NULL. How can I do this?

CustomerEntity customer = new CustomerEntity("ALFKI");
myAdapter.FetchEntity(customer);
customer.Address = null;
myAdapter.SaveEntity(customer);

Cool, but my field is not FK, so there is no related object, just int property in object model, which is not nullable. I guess I would have to have default value which would be saved as null. I will try as I wrote in my previous post. Thanks.

If it's not nullable in the entity, it's also not nullable in the DB. Or am I overlooking something obvious?

I understand, and totally agree. But, I have a project written and built in .Net 1.1, and LLBL 1.1. I think, if I'm not mistaken, that there were no nullable fields back then, thus not in the project, too. If I wanted to use LLBL V3 to generate existing code for that project, instead of V1, I would like to avoid changing other code that works with the entities, so I don't want nullable properties. I would like to have default values for them, to be saved as null, because that's the way the project works.

This is copied from V3's Breaking Changes section:

.NET 2.0: if an entity field is nullable, by default it is generated as a Nullable(of T) field. This means that if you read that field's property, you have to read the value into a Nullable(of T) typed variable as well. You can control this through the preferences and project properties by using the preference/project property GenerateNullableFieldsAsNullableTypes. This setting controls every new field's Generate as Nullable type setting. By default all the fields in your project will have that setting set to true, if they're nullable and a value type. To disable nullable fields for some fields, you can disable that for those fields in the entity editor. It's recommended to have all fields which are nullable as Nullable(Of T), and only disable this feature if your current code misuses the default value feature of the entity fields. Please see below as well how to detect that. A plug-in is included in the designer which allows you to set all the generate as nullable type flags of all the entity fields selected to a given value (true/false) so you can migrate your code from 1.0.2005.1 to v2.0 more easily, as having a lot of nullable types can break a lot of code.