NerdDinner的AddModelErrors如何工作？

Question

我正在阅读NerDinner免费教程 http://nerddinnerbook.s3.amazonaws.com/Intro.htm

我到了第5步的某个地方,它说要使代码更清晰,我们可以创建一个扩展方法.我查看完成的代码,并使用扩展方法:

catch
{
    ModelState.AddModelErrors(dinner.GetRuleViolations());
    return View(new DinnerFormViewModel(dinner));
}

然后这作为扩展方法的定义.

namespace NerdDinner.Helpers {

    public static class ModelStateHelpers {

        public static void AddModelErrors(this ModelStateDictionary modelState, IEnumerable<RuleViolation> errors) {

            foreach (RuleViolation issue in errors) {
                modelState.AddModelError(issue.PropertyName, issue.ErrorMessage);
            }
        }
    }
}

我尝试按照教程所说的结合代码包含的内容,但收到预期的错误,即没有AddModelErrors方法只接受1个参数.

我显然在这里缺少一些非常重要的东西.它是什么？

Answer 1

你需要包括助手参考;

using NerdDinner.Helpers;

和

using NerdDinner.Models;

然后检查有效并添加错误;

if (!dinner.IsValid)
{
    ModelState.AddModelErrors(dinner.GetRuleViolations());
    return View(dinner);
}

您还必须为您的晚餐准备一个部分课程;

public partial class Dinner
{
    public bool IsValid
    {
        get { return (GetRuleViolations().Count() == 0); }
    }

    public IEnumerable<RuleViolation> GetRuleViolations()
    {
        if (String.IsNullOrEmpty( SomeField ))
            yield return new RuleViolation("Field value text is required", "SomeField");
    }

    partial void OnValidate(ChangeAction action)
    {
        if (!IsValid)
            throw new ApplicationException("Rule violations prevent saving");
    }
}

别忘了RuleViolation上课;

public class RuleViolation
{
    public string ErrorMessage { get; private set; }
    public string PropertyName { get; private set; }

    public RuleViolation(string errorMessage)
    {
        ErrorMessage = errorMessage;
    }

    public RuleViolation(string errorMessage, string propertyName)
    {
        ErrorMessage = errorMessage;
        PropertyName = propertyName;
    }
}