如何在Entity Framework中处理可空的外键字段？ [英] How to handle a nullable foreign key field in Entity Framework?

问题描述

我有一个具有可空整数字段的表，它是一个外键。当我尝试将实体模型的Nullable属性设置为True时，我会收到一条错误，指出Int32类型的字段不能为null。因此，如果Entity Framework不支持可空整数，那么如何在空值中的表中插入行？如果没有为可空属性指定值，则Entity Framework会插入一个值0，因为外键约束会引起错误。

SQL Server可以使用可空的外部钥匙，所以我想保持支票约束到位。我的选择在这里？

提前感谢

解决方案

EF 支持可空的int。但int和int？是两种不同的类型。针对一个可空的int列生成一个新的模型，你会看到。

更新模型的原因并没有改变关联的多重性，因为EF更新时会尝试保留CSDL自定义。它将从头开始重新生成SSDL，并向CSDL添加任何新对象/关系，但不会覆盖您可能已经进行的更改。

I have a table with a nullable integer field that is a foreign key. When I try to set the entity model's Nullable property to True I get an error that states that fields of type Int32 can not be null. So if Entity Framework doesn't support nullable integers, how can I insert rows into the table with a null value? If no value is specified for the nullable property Entity Framework inserts a value of 0 which throws an error because of the foreign key constraint.

SQL Server is fine with a nullable foreign key so I'd like to keep the check constraint in place. What are my options here?

Thanks in advance!

解决方案

EF does support a nullable int. But int and int? are two different types. Generate a new model against a nullable int column and you'll see.

The reason that updating your model didn't change the multiplicity of the association is that the EF tries to preserve your CSDL customizations when you update. It will regenerate SSDL mostly from scratch, and add to the CSDL any new objects/relationships, but it doesn't overwrite changes you might have made.

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