ASP.NET MVC3：TryUpdateModel抛出异常

我有一个接受以下模型的视图：

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

这张贴回到以下操作：

    [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，在回发时引发以下异常：

无法将类型为“System.Int32”的对象转换为键入“System.String”。

说明：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该错误的更多信息以及源代码的位置。

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

源错误：

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

虽然我在这里不能突出显示，但发生异常的是第137行。 我无法步入此方法，因此如何确定导致此异常的原因？

另外，TryUpdateModel是否应该让我免受任何异常的影响，只是返回true或false来反映结果？ 我不知道它可能会引发异常。

更新：这里是模型（派生和基地）：

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，我能想到的最好的方式是显示它后面的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>

然后有一个好友类来扩展它：

[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，这里是视图的相关部分：

    <% 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>

<% } %>

---

不知道为什么这个异常在没有看到你的模型和视图代码的情况下发生，但是试着简化你的动作：

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

---

我改变了：

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

至：

public int? GroupID { get; set; }

所以StringLength属性造成了问题，因为GroupID是int？ 就像它看起来StringLength属性只对字符串有效。

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