实体字段的可为空属性，实体框架通过代码优先 [英] Nullable property to entity field, Entity Framework through Code First

问题描述

像这样使用数据注解Required:

[Required]
public int somefield {get; set;}

将数据库中的somefield设置为Not Null，如何设置somefield是否允许 NULL?，我尝试通过 SQL Server Management Studio 进行设置，但实体框架将其设置回 Not Null.

Will set somefield to Not Null in database, How can I set somefield to allow NULLs?, I tried setting it through SQL Server Management Studio but Entity Framework set it back to Not Null.

推荐答案

只需省略 string somefield 属性中的 [Required] 属性.这将使它在数据库中创建一个 NULLable 列.

Just omit the [Required] attribute from the string somefield property. This will make it create a NULLable column in the db.

要使 int 类型在数据库中允许 NULL，它们必须在模型中声明为可空的 int:

To make int types allow NULLs in the database, they must be declared as nullable ints in the model:

// an int can never be null, so it will be created as NOT NULL in db
public int someintfield { get; set; }

// to have a nullable int, you need to declare it as an int?
// or as a System.Nullable<int>
public int? somenullableintfield { get; set; }
public System.Nullable<int> someothernullableintfield { get; set; }

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