错误为可空INT分配空 - ＆QUOT;值'空'是无效的财产＆QUOT; [英] Error assigning null to a nullable int - "The value 'null' is not valid for property"

问题描述

我有这个属性在我的视图模型：

I have this property in my view model:

[DisplayName("Region")]
public int? RegionId { get; set; }

我通过我的视图模型为我的控制器，并在 ModelState.IsValid 失败，如果RegionId为null。如果我传递给它一个整数，它工作正常。

I pass my view model to my controller, and it fails at ModelState.IsValid if RegionId is null. If I pass an integer to it, it works fine.

错误消息是：

'空'的值不是有​​效的区域

The value 'null' is not valid for Region

我也试过在调用此我检查之前 ModelState.IsValid ，但我得到了同样的错误：

I've also tried calling this before I check ModelState.IsValid, but I get the same error:

if (viewModel.RegionId == null)
    viewModel.RegionId = (int?)null;

这里有什么问题吗？为什么我不能指定空的东西，可为空？

What's the problem here? Why can't I assign null to something that is nullable?

推荐答案

在你的Global.asax.cs文件，在Application_Start方法中，添加以下行：

In your Global.asax.cs file, in the Application_Start method, add the following line:

DataAnnotationsModelValidatorProvider.AddImplicitRequiredAttributeForValueTypes = false;

问题是，即使是空值类型，默认情况下，一个必需的属性由默认ValidatorProvider补充说。

The issue is that, even for a nullable value type, by default, a "Required" attribute is added by the default ValidatorProvider.

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