ASP.NET MVC 选择下拉列表，设置默认值并检索所选值答案

【问题标题】：ASP.NET MVC Select Drop Down list, set the default value and retrieve the selected valueASP.NET MVC 选择下拉列表，设置默认值并检索所选值
【发布时间】：2022-01-17 03:56:18
【问题描述】：

我相信答案很简单。我有一个带有值列表的<select>。对于编辑模式，我希望下拉菜单显示当前值并在视图呈现时选择。并且当表单提交时，获取一个可能的新选择值并将其传递回控制器。任何帮助将不胜感激。

从外观上看：

<td style="padding:15px">
    <label asp-for="OrganizationTypeId" class="form-control-label" style="font-weight:bold">Organization</label>
    <select asp-for="OrganizationTypeId" class="form-control" style="width:450px" asp-items="@(new SelectList(Model.orgTypes, "Id", "OrganizationName"))">
        <option value="" disabled hidden selected>Select Organization....</option>
    </select>
</td>

控制器中的代码：

dr = _electedOfficials.getDeputyReg(jurisdictionId, Id);

dr.orgTypes = _electedOfficials.GetOrganizationTypes(jurisdictionId);

return View(dr);

组织类型类

    public int Id { get; set; }
    public string OrganizationName { get; set; }

【问题讨论】：

标签： asp.net-mvc select

【解决方案1】：

其中一种解决方案是准备SelectListItem 的列表并将选定的项目Id 返回给控制器：

public ActionResult Index()
{
    // ...
    dr.orgTypes = _electedOfficials.GetOrganizationTypes(jurisdictionId);

    var model = dr.orgTypes.Select(d => new SelectListItem() { Selected = (d.Id == /* id of default selection*/), Text = d.OrganizationName, Value = d.Id.ToString() }).ToList(); 

    return View(model);
}

[HttpPost]
public ActionResult Index(int? seletedId)
{
    if (ModelState.IsValid && seletedId.HasValue)
    {
        // Processing the selected value...
    }           
    return RedirectToAction("Index");           
}

在视图中：

@model IEnumerable<SelectListItem>

<script type="text/javascript">

    $(document).ready(function () {
        var e = document.getElementById("OrgTypesList");
        $("#SeletedId").val(e.options[e.selectedIndex].value);
    });

    function changefunc(val) {
        $("#SeletedId").val($("#OrgTypesList").val());
    }
</script>

@using (Html.BeginForm("Index", "Home"))
{
    @* To pass `SeletedId` to controller *@
    <input id="SeletedId" name="SeletedId" type="hidden" />

    <label asp-for="OrganizationTypeId" class="form-control-label" style="font-weight:bold">Organization</label>
    @Html.DropDownList("OrgTypesList", Model, "Select Organization...", new { @class = "form-control", @onchange = "changefunc(this.value)" })

    <button type="submit" class="btn btn-primary">Save</button>
}

【讨论】：