ValidationMessageFor和AddModelError(key，message).关键是什么? [英] ValidationMessageFor together with AddModelError(key, message). What's the key?

问题描述

我正在为某个viewModel属性开发客户端和服务器端验证.

I am developing a client-side and server-side validation for a certain viewModel property.

在.cshtml文件中，我这样输入:

In the .cshtml file I put this:

@Html.DropDownListFor(model => model.EntityType.ParentId, Model.ParentTypeList, "")
@Html.ValidationMessageFor(model => model.EntityType.ParentId)

在Controller中用于业务验证

In the Controller for the business validation

catch (BusinessException e)
{
    ModelState.AddModelError("EntityType.ParentId", Messages.CircularReference);
}

以上内容按预期工作:如果捕获到异常，则消息显示在下拉列表旁边.

The above works as expected: if an exception is caught, the message appears next to the dropdownlist.

但是，我发现这种方式不是很优雅.在cshtml中，我使用一种方法来生成有关验证的所有必需信息.在控制器中，我必须知道确切的Key字符串并使用它.

However, I find that this way is not very elegant. In the cshtml, I use a method to generate all the required information about the validation. In the controller, I must know the exact Key string and use it.

没有更好的方法吗?

推荐答案

您可以编写一个扩展方法，该方法将使用lambda表达式作为键而不是字符串:

You could write an extension method that will take a lambda expression for the key instead of a string:

public static class ModelStateExtensions
{
    public static void AddModelError<TModel, TProperty>(
        this ModelStateDictionary modelState, 
        Expression<Func<TModel, TProperty>> ex, 
        string message
    )
    {
        var key = ExpressionHelper.GetExpressionText(ex);
        modelState.AddModelError(key, message);
    }
}

然后使用此方法:

catch (BusinessException e)
{
    ModelState.AddModelError<MyViewModel, int>(
        x => x.EntityType.ParentId, 
        Messages.CircularReference
    );
}

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