ASP.NET MVC3：TryUpdateModel 抛出异常

Question

我有一个接受以下模型的视图：

Inherits="System.Web.Mvc.ViewPage<MVC_WordsByME.Models.JobCreationModel>"

这会回发到以下操作：

    [HttpPost]
    public ActionResult Create(FormCollection formValues)
    {
        var job = new JobCreationModel();
        if (TryUpdateModel(job))
        {
            _jobRepository.AddJob(job);
            _jobRepository.Save();
            return RedirectToAction("Index");
        }
        return View(job);
    }

但是，回发时会引发以下异常：

无法将“System.Int32”类型的对象转换为“System.String”类型。

描述：执行当前 Web 请求期间发生未处理的异常。 请查看堆栈跟踪以获取有关错误及其在代码中的来源的更多信息。

异常详细信息：System.InvalidCastException：无法将“System.Int32”类型的对象转换为“System.String”类型。

来源错误：

Line 135:        {
Line 136:            var job = new JobCreationModel();
Line 137:            if (TryUpdateModel(job))
Line 138:            {
Line 139:                _jobRepository.AddJob((Job)job);

虽然我无法在这里突出显示它，但异常发生在第 137 行。我无法进入该方法，那么如何确定导致此异常的原因呢？

另外，TryUpdateModel 不是应该让我免受任何异常的影响，只需返回 true 或 false 来反映结果吗？我不知道它可能抛出异常。

更新：这是模型（派生的和基本的）：

public class JobCreationModel : Job
{
    //
    // Properties

    public SelectList ClientsList { get; private set; }
    public SelectList Languages { get; set; }
    public SelectList Users { get; set; }


    //
    // Constructors

    public JobCreationModel()
    {
        var userCurrent = Membership.GetUser();

        SentDate = DateTime.Now;
        WorkedBy = userCurrent != null ? userCurrent.UserName : string.Empty;
        DeadlineDate = DateTime.Now;
        ReceivedDate = DateTime.Now;

        var clientRepository = new ClientRepository();
        ClientsList = new SelectList(clientRepository.GetAllClients(), "ID", "OrganisationName");

        var languageRepository = new LanguageRepository();
        Languages = new SelectList(languageRepository.GetAllLanguages(), "ID", "Code");

        var userList = Membership.GetAllUsers();
        Users = new SelectList(userList.Cast<MembershipUser>().ToList(), "UserName", "UserName", userCurrent);
    }

    public JobCreationModel(Job job)
    {
        var userCurrent = Membership.GetUser();

        Client = job.Client;
        ClientName = job.ClientName;
        DeadlineDate = job.DeadlineDate;
        FixedCost = job.FixedCost;
        ID = job.ID;
        Invoice = job.Invoice;
        JobDescription = job.JobDescription;
        JobFileName = job.JobFileName;
        LanguageFrom = job.LanguageFrom;
        LanguageTo = job.LanguageTo;
        PONumber = job.PONumber;
        ReceivedDate = job.ReceivedDate;
        SentDate = job.SentDate;
        WordCost = job.WordCost;
        WordCount = job.WordCount;
        WorkedBy = job.WorkedBy;

        var clientRepository = new ClientRepository();
        ClientsList = new SelectList(clientRepository.GetAllClients(), "ID", "OrganisationName");

        var languageRepository = new LanguageRepository();
        Languages = new SelectList(languageRepository.GetAllLanguages(), "ID", "Code");

        var userList = Membership.GetAllUsers();
        Users = new SelectList(userList.Cast<MembershipUser>().ToList(), "UserName", "UserName", userCurrent);
    }
}

基本类型是一个实体，我能想到的显示它的最好方法是显示它后面的 XML：

<EntityType Name="Jobs">
      <Key>
        <PropertyRef Name="ID" />
      </Key>
      <Property Name="ID" Type="int" Nullable="false" StoreGeneratedPattern="Identity" />
      <Property Name="JobDescription" Type="nvarchar" Nullable="false" MaxLength="200" />
      <Property Name="ReceivedDate" Type="datetime" Nullable="false" />
      <Property Name="DeadlineDate" Type="datetime" Nullable="false" />
      <Property Name="SentDate" Type="datetime" Nullable="false" />
      <Property Name="Invoice" Type="int" />
      <Property Name="WordCount" Type="int" Nullable="false" />
      <Property Name="WordCost" Type="float" Nullable="false" />
      <Property Name="FixedCost" Type="float" Nullable="false" />
      <Property Name="Client" Type="int" Nullable="false" />
      <Property Name="JobFileName" Type="nvarchar" Nullable="false" MaxLength="500" />
      <Property Name="WorkedBy" Type="varchar" Nullable="false" MaxLength="50" />
      <Property Name="PONumber" Type="varchar" Nullable="false" MaxLength="50" />
      <Property Name="LanguageFrom" Type="int" Nullable="false" />
      <Property Name="LanguageTo" Type="int" Nullable="false" />
    </EntityType>

然后有一个伙伴类来扩展它：

[MetadataType(typeof(JobValidation))]
[Bind(Include = "Client,SentDate,JobFileName,JobDescription,WordCost,WordCount,WorkedBy")]
public partial class Job
{
    public IEnumerable Clients
    {
        get
        {
            var clientRepository = new ClientRepository();
            return clientRepository.GetAllClients();
        }
    }
    public string ClientName { get; set; }
    public string SelectedMonth { get; set; }
    public string SelectedYear { get; set; }
}

public class JobValidation
{
    [Required(ErrorMessage = "Please select a client for the sent job")]
    [Range(1, 999999, ErrorMessage = "Please select a client")]
    public int Client { get; set; }

    [Required(ErrorMessage = "Please enter the completion date for this job")]
    [DataType(DataType.Date, ErrorMessage = "The date entered is not in a recognised format")]
    public DateTime SentDate { get; set; }

    [Required(ErrorMessage = "Job file must have a name")]
    [StringLength(500, ErrorMessage = "Job file name must not be longer than 500 characters")]
    public string JobFileName { get; set; }

    [Required(ErrorMessage = "Job must have a name")]
    [StringLength(200, ErrorMessage = "Job name must not be longer than 200 characters")]
    public string JobDescription { get; set; }

    [Required(ErrorMessage = "Please enter the word cost for the sent job")]
    [StringLength(6, ErrorMessage = "The word cost should not exceed 5 digits")]
    [DataType(DataType.Currency, ErrorMessage = "The word cost was not recognised as an amount of currency")]
    public string WordCost { get; set; }

    [Required(ErrorMessage = "Please enter the word count for the sent job")]
    [StringLength(8, ErrorMessage = "The word count must not exceed 99999999")]
    public string WordCount { get; set; }

    public string WorkedBy { get; set; }
}

最后，这是视图的相关部分：

    <% using (Html.BeginForm()) {%>
    <%: Html.ValidationSummary(true) %>

    <fieldset>
        <legend>Job Details</legend>

        <div class="editor-label">
            Job description
        </div>
        <div class="editor-field">
            <%: Html.TextBoxFor(model => model.JobDescription)%>
            <%: Html.ValidationMessageFor(model => model.JobDescription)%>
        </div>

        <div class="editor-label">
            PO number
        </div>
        <div class="editor-field">
            <%: Html.TextBoxFor(model => model.PONumber)%>
            <%: Html.ValidationMessageFor(model => model.PONumber)%>
        </div>

        <div class="editor-label">
            Date received
        </div>
        <div class="editor-field">
            <%: Html.TextBoxFor(model => model.ReceivedDate)%>
            <%: Html.ValidationMessageFor(model => model.ReceivedDate)%>
        </div>

        <div class="editor-label">
            Deadline Date
        </div>
        <div class="editor-field">
            <%: Html.TextBoxFor(model => model.DeadlineDate)%>
            <%: Html.ValidationMessageFor(model => model.DeadlineDate)%>
        </div>

        <div class="editor-label">
            Date sent
        </div>
        <div class="editor-field">
            <%: Html.TextBoxFor(model => model.SentDate)%>
            <%: Html.ValidationMessageFor(model => model.SentDate)%>
        </div>

        <div class="editor-label">
            Is fixed-cost?&nbsp;<input type="checkbox" id="fixed-cost" />
        </div>

        <div id="word-priced-job">
            <div class="editor-label">
                Word count
            </div>
            <div class="editor-field">
                <%: Html.TextBoxFor(model => model.WordCount)%>
                <%: Html.ValidationMessageFor(model => model.WordCount)%>
            </div>

            <div class="editor-label">
                Word cost
            </div>
            <div class="editor-field">
                <%: Html.TextBoxFor(model => model.WordCost)%>
                <%: Html.ValidationMessageFor(model => model.WordCost)%>
            </div>
        </div>

        <div id="fixed-price-job" class="faded">
            <div class="editor-label">
                Fixed cost
            </div>
            <div class="editor-field">
                <%: Html.TextBoxFor(model => model.FixedCost)%>
                <%: Html.ValidationMessageFor(model => model.FixedCost)%>
            </div>
        </div>

        <div class="editor-label">
            Languages
        </div>
        <div class="editor-field">
            <%: Html.DropDownListFor(model => model.LanguageFrom, Model.Languages, "-- Select --") %><%: Html.ValidationMessageFor(model => model.LanguageFrom)%>
            <span>&nbsp;-&nbsp;to&nbsp;-&nbsp;</span>
            <%: Html.DropDownListFor(model => model.LanguageTo, Model.Languages, "-- Select --") %><%: Html.ValidationMessageFor(model => model.LanguageTo)%>
        </div>

        <div class="editor-label">
            Client
        </div>
        <div class="editor-field">
            <%: Html.DropDownListFor(model => model.Client, Model.ClientsList, "-- Select --") %> <%: Html.ActionLink("Create a new client", "Create", "Clients") %>
            <%: Html.ValidationMessageFor(model => model.Client)%>
        </div>

        <div class="editor-label">
            Job file name
        </div>
        <div class="editor-field">
            <%: Html.TextBoxFor(model => model.JobFileName) %>
            <%: Html.ValidationMessageFor(model => model.JobFileName)%>
        </div>

        <div class="editor-label">
            <%: Html.LabelFor(model => model.WorkedBy)%>
        </div>
        <div class="editor-field">
            <%: Html.DropDownListFor(model => model.WorkedBy, Model.Users) %>
        </div>

        <p>
            <input id="btnSave" type="submit" value="Save" />
        </p>
    </fieldset>

<% } %>

Answer 1

在没有看到模型和视图代码的情况下不知道为什么会发生此异常，但请尝试像这样简化您的操作：

[HttpPost]
public ActionResult Create(JobCreationModel job)
{
    if (!ModelState.IsValid)
    {
        return View(job);
    }
    _jobRepository.AddJob(job);
    _jobRepository.Save();
    return RedirectToAction("Index");
}

Answer 2

我已将： 更改

[StringLength(3)]
public int? GroupID { get; set; }

为：

public int? GroupID { get; set; }

那么 StringLength 属性会产生问题，因为 GroupID 是 int？看来 StringLength 属性仅对字符串有效。