如何在本地查看模型绑定异常

Question

我有一个ASP.NET网络应用程序运行在一个Azure应用服务。

在进行了分析器跟踪之后，我注意到了以下三个.NET异常：

Requested value 'Asc' was not found.

Asc is not a valid value for SortOrder.

The parameter conversion from type 'System.String' to type 'Enums.SortOrder' failed. See the inner exception for more information.

它们都有这样的堆栈跟踪：

mscorlib.ni![COLD] System.Enum+EnumResult.SetFailure
mscorlib.ni!System.Enum.Parse
system.ni!
system.web.http!System.Web.Http.ValueProviders.ValueProviderResult.ConvertSimpleType
system.web.http!System.Web.Http.ValueProviders.ValueProviderResult.UnwrapPossibleListType
system.web.http!System.Web.Http.ValueProviders.ValueProviderResult.ConvertTo
system.web.http!System.Web.Http.ModelBinding.Binders.TypeConverterModelBinder.BindModel
system.web.http!System.Web.Http.Controllers.HttpActionContextExtensions.Bind
system.web.http!System.Web.Http.ModelBinding.Binders.CompositeModelBinder.BindModel
system.web.http!System.Web.Http.ModelBinding.ModelBinderParameterBinding.ExecuteBindingAsync
system.web.http!System.Web.Http.Controllers.HttpActionBinding+<ExecuteBindingAsyncCore>d__12.MoveNext
mscorlib!System.Runtime.CompilerServices.AsyncTaskMethodBuilder.Start
system.web.http!System.Web.Http.Controllers.HttpActionBinding.ExecuteBindingAsyncCore
system.web.http!System.Web.Http.Controllers.HttpActionBinding.ExecuteBindingAsync
system.web.http!System.Web.Http.Controllers.ActionFilterResult+<ExecuteAsync>d__5.MoveNext
mscorlib!System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1[System.__Canon].Start
system.web.http!System.Web.Http.Controllers.ActionFilterResult.ExecuteAsync
system.web.http!System.Web.Http.ApiController.ExecuteAsync
system.web.http!System.Web.Http.Dispatcher.HttpControllerDispatcher+<SendAsync>d__15.MoveNext
mscorlib!System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1[System.__Canon].Start
system.web.http!System.Web.Http.Dispatcher.HttpControllerDispatcher.SendAsync
system.net.http.ni!
system.web.http!System.Web.Http.Dispatcher.HttpRoutingDispatcher.SendAsync
system.net.http.ni!
autofac.integration.webapi!Autofac.Integration.WebApi.CurrentRequestHandler.SendAsync
system.net.http.ni!
Rend.invgen.invoicegateway.api!Rend.invgen.InvoiceGateway.Api.Handlers.RequestResponseLogHandler.SendNextAsync
Rend.invgen.invoicegateway.api!Rend.invgen.InvoiceGateway.Api.Handlers.RequestResponseLogHandler+<>c__DisplayClass0_0.<SendAsync>b__0
mscorlib.ni!System.Threading.Tasks.Task.Execute
mscorlib.ni!System.Threading.Tasks.Task.ExecutionContextCallback
mscorlib.ni!System.Threading.ExecutionContext.Run
mscorlib.ni!System.Threading.Tasks.Task.ExecuteWithThreadLocal
mscorlib.ni!System.Threading.Tasks.Task.ExecuteEntry
mscorlib.ni!System.Threading.Tasks.SynchronizationContextTaskScheduler.PostCallback
system.web.ni!
mscorlib.ni!System.Threading.Tasks.Task.Execute
mscorlib.ni!System.Threading.Tasks.Task.ExecutionContextCallback
mscorlib.ni!System.Threading.ExecutionContext.Run
mscorlib.ni!System.Threading.Tasks.Task.ExecuteWithThreadLocal
mscorlib.ni!System.Threading.Tasks.Task.ExecuteEntry
mscorlib.ni!System.Threading.Tasks.Task.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem
mscorlib.ni!System.Threading._ThreadPoolWaitCallback.PerformWaitCallback

引起此问题的我的操作方法如下：

public async Task<IHttpActionResult> GetAsync(SortOrder sort = SortOrder.Ascending)
{
    // sort something
}

使用参数(如Asc )调用此操作方法。

尽管这似乎会导致.NET异常，但如果不能绑定值，则会使用Ascending的默认值。

我的问题是，为什么我不能在本地查看Requested value Asc was not found异常？

当我在本地运行应用程序并通过Asc和Desc时，不会抛出任何异常，在Debug窗口中也看不到任何异常。

Answer 1

默认情况下，绑定Enum需要与该值相对应的整数值。

如果您想提供一个string值，您必须通过向Enum类型声明添加一个属性来告诉模型绑定器，如下所示：

[ModelBinder(BinderType = typeof(EnumModelBinder))]
public enum SortOrder
{
}

也可以在模型中向属性添加属性，如下所示：

[BindProperty(BinderType = typeof(EnumModelBinder))]
public SortOrder MySortOrder {get;set;}

现在，模型绑定应该能够处理字符串。当然，字符串必须与枚举值完全匹配。

BTW:失败的Modelbinding不会抛出异常，它只是忽略了值，这意味着属性将获得它们的默认值。

Answer 2

我已复制并能够解决，请遵循以下步骤

下面的

• 是文件夹结构

​

​

ActionModel.cs

• 将数据绑定到我们使用的操作模型

的视图。

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Data.SqlClient;
using System.Linq;
using System.Threading.Tasks;
using System.Web.Http;
using System.Web.Mvc;

namespace MVC_Sort
{
    public class ActionModel
    {
        public ActionModel()
        {
            ActionsList = new List<SelectListItem>();
        }
        [Display(Name="Names")]
        public int ActionId { get; set; }

        public IEnumerable<SelectListItem> ActionsList { get; set; }       
    }
}

ActionType.cs

• 按排序顺序显示的Enum列表

namespace MVC_Sort
{
    public enum ActionType
    {
        MMM = 1,
        RRR = 2,
        AAA = 3,
        JJJ = 4,
        EEE = 5,
        SSS = 6,
        HHH = 7
    }

}

ActionTypeModel.cs

视图中的

• 用于显示输出

中的Enum值和标签名称。

using System.ComponentModel.DataAnnotations;
namespace MVC_Sort
{
    public class ActionTypeModel
    {
        [Display(Name = "Names")]
        public int ActionId { get; set; }
        public ActionType ActionTypeList { get; set; }
    }
}

HomeController.cs

HomeController中的操作方法在请求时执行

namespace MVC_Sort.Controllers
{
    public class HomeController : Controller
    {
        public ActionResult Index()
        {
            ActionModel model = new ActionModel();
            IEnumerable<ActionType> actionTypes = Enum.GetValues(typeof(ActionType))
                                                       .Cast<ActionType>();

            var res= actionTypes.OrderBy(enm => enm.ToString()).ToArray();

            model.ActionsList = from action in res
                                select new SelectListItem
                                {
                                    Text = action.ToString(),
                                    Value = ((int)action).ToString()
                                };

            return View(model);
        }

        public ActionResult ActionTypes()
        {
            ActionTypeModel model = new ActionTypeModel();
            return View(model);
        }
    }
}

Index.cshtml

• 是执行

时显示的Html页面

model MVC_Sort.ActionModel
@{
    ViewBag.Title = "Index";
}

@Html.LabelFor(model=>model.ActionId)
@Html.DropDownListFor(model=>model.ActionId, Model.ActionsList)

Extension.cs

它用于从ActionType获取或检索Enum值。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Web.Mvc;
using System.Web.Mvc.Html;

namespace MVC_Sort
{
    public static class Extension
    {

        public static MvcHtmlString EnumDropDownListFor<TModel, TProperty, TEnum>(this HtmlHelper<TModel> htmlHelper,
                                                                                    Expression<Func<TModel, TProperty>> expression, 
                                                                                    TEnum selectedValue)
        {
            IEnumerable<TEnum> values = Enum.GetValues(typeof(TEnum))
                                        .Cast<TEnum>();

            IEnumerable<SelectListItem> items = from value in values
                                                select new SelectListItem()
                                                {
                                                    Text = value.ToString(),
                                                    Value = value.ToString(),
                                                    Selected = (value.Equals(selectedValue))
                                                };

            return SelectExtensions.DropDownListFor(htmlHelper,expression, items);
        }
    }
}

• 在上述步骤之后单击debug => 开始调试。之后，它将按排序顺序在浏览器中打开下面的一个

​

​