是否可以表达检查约束？ [英] Is it possible to express a check constraint?

问题描述

我正在使用Entity Framework 4.3进行代码优先开发，似乎不可能表达一个 CHECK约束通过属性注释，或者任何其他方式。我看到EF 5.0将添加对检查枚举，但这不完全是我在这里之后。

I'm doing code-first development with Entity Framework 4.3 and it doesn't seem like it's possible to express a CHECK constraint via attribute annotations or, well, any other means. I see that EF 5.0 will be adding support for checking enumerations, but that's not exactly what I'm after here.

为了给出一个简化的例子，我想验证所有 Person 对象的名字为Bob或Harry，为5,10或30岁。

To give a simplified example, I'd like to validate that all Person objects have a first name of either "Bob" or "Harry" and are either 5, 10 or 30 years old.

public class Person
{
    [Required]
    [Check("Bob", "Harry")]  //yes, this attribute is imaginary
    public string FirstName { get; set; }

    [Required, Check(5, 30, 50)]  //check is still imaginary
    public int Age { get; set; }
}

我可以运行一个alter script来添加这些约束，可以滚动自己的检查属性来执行验证，但是在实体框架中有没有实际表达非枚举的CHECK约束的方法？

I can run an alter script to add these constraints after the fact and I can roll my own check attribute to perform validations, but is there a way I'm missing to actually express non-enumerated CHECK constraints in Entity Framework?

推荐答案

你可以自己写一个（未经测试）：

You could write one yourself (untested):

public class CheckAttribute : System.ComponentModel.DataAnnotations.ValidationAttribute
{
    object[] ValidValues;

    public CheckAttribute<T>(params T[] validValues)
    {
        ValidValues = validValues;
    }

    public override bool IsValid(object value)
    {
        return ValidValues.FirstOrDefault(v => v.Equals(value)) != null;
    }
}

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