Question

在mvc中的绑定下拉列表中我总是会收到此错误没有类型＆＃39; IEnumerable＆＃39;有钥匙的国家，我不知道如何分类

查看

@Html.DropDownList("country",
    (IEnumerable<SelectListItem>)ViewBag.countrydrop,"Select country")

控制器

List<Companyregister> coun = new List<Companyregister>();
coun = ds.getcountry();

List<SelectListItem> item8 = new List<SelectListItem>();
foreach( var c in coun )
{
    item8.Add(new SelectListItem
    {
        Text = c.country,
        Value = c.countryid.ToString()
    });
}

ViewBag.countrydrop = item8;
return View();

我不知道我错在哪里，任何人都可以提前帮助我

Answer 1

在您的操作中，将ViewBag.countrydrop = item8更改为ViewBag.country = item8;，然后在View中写下：

@Html.DropDownList("country",
                   (IEnumerable<SelectListItem>)ViewBag.country,
                   "Select country")

实际上当你写

<强> @ Html.DropDownList（ “国家”，                            （IEnumerable的）ViewBag.country，                            “选择国家/地区”）

或

Html.DropDownList（“country”，“Select Country”

它在IEnumerable<SelectListItem>中使用键国家查找ViewBag，在这种情况下您也可以使用此重载：

@Html.DropDownList("country","Select country") // it will look for ViewBag.country and populates dropdown

请参阅Working DEMO Example

Answer 2

如果你这样使用DropDownListFor：

@Html.DropDownListFor(m => m.SelectedItemId, Model.MySelectList)

其中模型中的MySelectList是SelectList类型的属性，如果属性为null，则可能会抛出此错误。

通过在构造函数中简单地初始化它来避免这种情况，如下所示：

public MyModel()
{
    MySelectList = new SelectList(new List<string>()); // empty list of anything...
}

我知道这不是OP的情况，但这可能会帮助像我这样的人因此而出现同样的错误。

Answer 3

请注意，选择列表会发布为null，因此您的错误会导致无法找到viewdata属性。

始终在POST操作中重新初始化您的选择列表。

进一步说明： Persist SelectList in model on Post

Answer 4

使用此

 var list = new SelectList(countryList, "Id", "Name");
 ViewBag.countries=list;
 @Html.DropDownList("countries",ViewBag.Roles as SelectList)

Answer 5

试试这个

@Html.DropDownList("ddlcountry",(List<SelectListItem>)ViewBag.countrydrop,"Select country")

在控制器

中

ViewBag.countrydrop = ds.getcountry().Select(x => new SelectListItem { Text = x.country, Value = x.countryid.ToString() }).ToList();

Answer 6

我遇到了同样的问题，我找到了解决方案，我应该把代码放在编辑方法中从数据库中检索下拉列表。它对我有用。 Solution for the similar problem

Answer 7

在我的情况下，发生错误是因为我没有在控制器中初始化选择列表，如下所示：

viewModel.MySelectList = new List<System.Web.Mvc.SelectListItem>();

由于现有的答案都没有向我说明，我发布了这个。也许它可以帮助任何人。

Answer 8

你的代码是正确的，因为在某些情况下它不起作用，我也不知道错误来自哪里，但这可以帮助你解决问题，将代码移动到视图的头部，如下所示：

[86429.875904]  # GUEST_ES_SEL = 0x0
[86429.875905]  # GUEST_CS_SEL = 0x0
[86429.875905]  # GUEST_SS_SEL = 0x0
[86429.875906]  # GUEST_DS_SEL = 0x0
[86429.875907]  # GUEST_FS_SEL = 0x0
[86429.875907]  # GUEST_GS_SEL = 0x0
[86429.875908]  # GUEST_LDTR_SEL = 0x0
[86429.875908]  # GUEST_TR_SEL = 0x0
[86429.875909]  # GUEST_INTERRUPT_STATUS = 0x0
[86429.876003]  # GUEST_PHYSICAL_ADDR_FULL = 0x0
[86429.876004]  # GUEST_PHYSICAL_ADDR_HIGH = 0x0
[86429.876006]  # VMCS_LINK_PTR_FULL = 0xffffffffffffffff
[86429.876007]  # VMCS_LINK_PTR_HIGH = 0xffffffff
[86429.876009]  # GUEST_IA32_DEBUGCTL_FULL = 0x0
[86429.876010]  # GUEST_IA32_DEBUGCTL_HIGH = 0x0
[86429.876012]  # GUEST_IA32_PAT_FULL = 0x0
[86429.876013]  # GUEST_IA32_PAT_HIGH = 0x0
[86429.876015]  # GUEST_IA32_EFER_FULL = 0x0
[86429.876017]  # GUEST_IA32_EFER_HIGH = 0x0
[86429.876018]  # GUEST_IA32_PERF_CTL_FULL = 0x0
[86429.876020]  # GUEST_IA32_PERF_CTL_HIGH = 0x0
[86429.876020]  # GUEST_PDPTE0_FULL = 0x0
[86429.876021]  # GUEST_PDPTE0_HIGH = 0x0
[86429.876022]  # GUEST_PDPTE1_FULL = 0x0
[86429.876022]  # GUEST_PDPTE1_HIGH = 0x0
[86429.876023]  # GUEST_PDPTE2_FULL = 0x0
[86429.876024]  # GUEST_PDPTE2_HIGH = 0x0
[86429.876025]  # GUEST_PDPTE3_FULL = 0x0
[86429.876025]  # GUEST_PDPTE3_HIGH = 0x0
[86429.876067]  # EXIT_INTERRUPT_INFO = 0x0
[86429.876067]  # EXIT_INTERRUPT_ERRCODE = 0x0
[86429.876068]  # IDT_VECTORING_INFO_FIELD = 0x0
[86429.876069]  # IDT_VECTORING_ERRCODE = 0x0
[86429.876069]  # EXIT_INSTR_LEN = 0x0
[86429.876070]  # INSTR_INFO = 0x0
[86429.876070]  # GUEST_ES_LIMIT = 0xffff
[86429.876071]  # GUEST_CS_LIMIT = 0xffff
[86429.876072]  # GUEST_SS_LIMIT = 0xffff
[86429.876072]  # GUEST_DS_LIMIT = 0xffff
[86429.876073]  # GUEST_FS_LIMIT = 0xffff
[86429.876074]  # GUEST_GS_LIMIT = 0xffff
[86429.876075]  # GUEST_LDTR_LIMIT = 0xffff
[86429.876075]  # GUEST_TR_LIMIT = 0xffff
[86429.876076]  # GUEST_GDTR_LIMIT = 0xffff
[86429.876077]  # GUEST_IDTR_LIMIT = 0xffff
[86429.876077]  # GUEST_ES_ATTR = 0x93
[86429.876078]  # GUEST_CS_ATTR = 0x9b
[86429.876078]  # GUEST_SS_ATTR = 0x93
[86429.876079]  # GUEST_DS_ATTR = 0x93
[86429.876080]  # GUEST_FS_ATTR = 0x93
[86429.876080]  # GUEST_GS_ATTR = 0x93
[86429.876081]  # GUEST_LDTR_ATTR = 0x82
[86429.876081]  # GUEST_TR_ATTR = 0x8b
[86429.876082]  # GUEST_INTERRUPTIBILITY_INFO = 0x0
[86429.876084]  # GUEST_ACTIVITY_STATE = 0x0
[86429.876085]  # GUEST_SMBASE = 0x0
[86429.876086]  # GUEST_IA32_SYSENTER_CS = 0x0
[86429.876087]    # vmread(0x482E) failed
[86429.876088]    # RFLAGS: 0x242
[86429.876088]  # GUEST_PREEMTION_TIMER          INVALID_VALUE
[86429.876090]  # HOST_IA32_SYSENTER_CS = 0x10
[86429.876092]  # CR0_MASK = 0xfffffffffffffff0
[86429.876093]  # CR4_MASK = 0xfffffffffffff871
[86429.876095]  # CR0_READ_SHADOW = 0x60000010
[86429.876096]  # CR4_READ_SHADOW = 0x10
[86429.876097]  # CR3_TARGET_0 = 0x0
[86429.876099]  # CR3_TARGET_1 = 0x23341e000
[86429.876101]  # CR3_TARGET_2 = 0x0
[86429.876102]  # CR3_TARGET_3 = 0x0
[86429.876103]  # EXIT_QUALIFICATION = 0x0
[86429.876104]  # IO_RCX = 0x0
[86429.876104]  # IO_RSI = 0x0
[86429.876105]  # IO_RDI = 0x0
[86429.876105]  # IO_RIP = 0x0
[86429.876106]  # GUEST_LINEAR_ADDR = 0x0
[86429.876108]  # GUEST_CR0 = 0x50032
[86429.876108]  # GUEST_CR3 = 0x0
[86429.876109]  # GUEST_CR4 = 0x2050
[86429.876110]  # GUEST_ES_BASE = 0x0
[86429.876110]  # GUEST_CS_BASE = 0x0
[86429.876111]  # GUEST_SS_BASE = 0x0
[86429.876111]  # GUEST_DS_BASE = 0x0
[86429.876112]  # GUEST_FS_BASE = 0x0
[86429.876112]  # GUEST_GS_BASE = 0x0
[86429.876113]  # GUEST_LDTR_BASE = 0x0
[86429.876114]  # GUEST_TR_BASE = 0x0
[86429.876114]  # GUEST_GDTR_BASE = 0x0
[86429.876115]  # GUEST_IDTR_BASE = 0x0
[86429.876117]  # GUEST_DR7 = 0x400
[86429.876118]  # GUEST_RSP = 0x7bfa
[86429.876118]  # GUEST_RIP = 0x7c00
[86429.876119]  # GUEST_RFLAGS = 0x2
[86429.876120]  # GUEST_PENDING_DEBUG_EXCEPT = 0x0
[86429.876120]  # GUEST_IA32_SYSENTER_ESP = 0x0
[86429.876121]  # GUEST_IA32_SYSENTER_EIP = 0x0

Answer 9

尝试一下。

控制器：

List<CountryModel> countryList = db.countryTable.ToList();
ViewBag.Country = new SelectList(countryList, "Country", "CountryName");

Answer 10

在您的视图中，将"country"替换为"countrydrop"，就像这样...

@Html.DropDownList("countrydrop", (IEnumerable<SelectListItem>)ViewBag.countrydrop,"Select country")

Answer 11

您正面临此问题，因为在发布表单时，重新加载下拉列表后无法在viewbag中找到数据。因此，在从db或静态列表中检索数据时，请确保要在get方法中使用的代码，并将该代码也复制粘贴到post verb中。

快乐编码：）

Answer 12

可能类似于 ASP.NET MVC 框架

@Html.DropDownList("country", ViewBag.countrydrop as List<SelectListItem>,"Select country")

或 ASP.NET Core MVC

<select class="class" id="country"
asp-items="@(new SelectLits(ViewBag.countrydrop,"Value","Text"))">

没有类型为'IEnumerable <selectlistitem>'的ViewData项具有关键国家/地区</selectlistitem>

12 个答案: