jQuery創建的ASP.NET Core 2.1填充下拉列表

Question

我有這個按鈕，當單擊該按鈕時，將創建一個包含多個下拉列表的新div行。 如何從加載到我的視圖的viewmodel中填充這些下拉菜單？

@model App.Data.ViewModels.FilterDocumentsViewModel

<button type="button" class="btn btn-outline-secondary" data-toggle="collapse" data-target="#datatable-search-input-container-rowtwo" aria-expanded="false" aria-controls="datatable-search-input-container-rowtwo">
        <i class="fa fa-plus"></i>
</button>

$("#datatable-search-input-container-rowone-coltwo").on("click", "#add-row", function (e) {
    var htmlElements = "<div class='col-sm-10 row'>";
    htmlElements = htmlElements + "<div class='col-sm-3 search-spacing'>";
    htmlElements = htmlElements + "<label>Document Categories</label>";
    htmlElements = htmlElements + "<select class='form-control' name='CategoryId[]' asp-items='@Model.Categories'>Select Category</select>"
    htmlElements = htmlElements + "<label>Document Fields</label>";
    htmlElements = htmlElements + "<select class='form-control' name='FieldId[]' asp-items='@Model.DocumentFields'>Select Document Fields</select>"
    htmlElements = htmlElements + "</div>";
    htmlElements = htmlElements + "</div>";
    $(htmlElements).appendTo("#datatable-search-input-container-rowone-colone-sub");
    return false;
});

我上面的內容只創建了一個空的下拉列表。 另外，是否可以對文檔類別進行onchange，以重新填充文檔字段？

編輯：基於@TetsuyaYamamotos的答案，這就是我所做的

PartialView：

@model App.Data.ViewModels.FilterDocumentsViewModel
<div class="col-sm-12 row">
    <div class="col-sm-3 search-spacing">
        <label>Document Categories</label>
        @Html.DropDownListFor(m => m.CategoryId, (SelectList)Model.Categories, "Select Category", new { @class = "form-control Categories" })
    </div>
    <div class="col-sm-3 search-spacing">
        <label>Document Fields</label>
        @Html.DropDownListFor(m => m.FieldId, (SelectList)Model.DocumentFields, "Select Field", new { @class = "form-control Fields" })
    </div>
    <div class="col-sm-3 search-spacing">
        <label for="Data">Data</label>
        <input type="text" id="Data" placeholder="Search" />
    </div>
</div>

jQuery的：

function refreshDropdown(Input) {
    $.ajax({
            url: "@Url.Action("GetFields", @ViewContext.RouteData.Values["controller"].ToString())",
            method: "POST",
            data: JSON.stringify(Input),
            contentType: "application/json",
            success: function (result) {
                $(".Fields").empty();
                $(".Fields").append("<option value>Select Field</option>");
                $.each(result.fields, function (key, value) {
                    $(".Fields").append("<option value="+value.Id+">"+value.Name+"</option>");
                });
            },
            error: function (error) {
                console.log(error);
            }
        });
}

$("#datatable-search-input-container").on("change", ".Categories", function (e) {
    console.log("changed");
    selected = $(".Categories").find(":selected").val();
    var form_data = selected;
    refreshDropdown(form_data);
    return false;
});

添加行：

$("#datatable-search-input-container-rowone-coltwo").on("click", "#add-row", function (e) {
    $.ajax({
        url: "@Url.Action("AddSearchFilterRow", @ViewContext.RouteData.Values["controller"].ToString())",
        method: "GET",
        contentType: "application/json",
        success: function (result) {
            $(result).appendTo("#datatable-search-input-container-rowone-colone-sub");
        },
        error: function (error) {
            console.log(error);
        }
    });
    return false;
});

剩下的唯一問題是，唯一起作用的onchange是主要變量，而不是更改時添加的jquery

Answer 1

您可以將數據從viewmodel獲取到javascript對象中，然后使用jquery遍歷該數據

var modelCategories = @Html.Raw(Json.Encode(Model.Categories));
var modelDocumentFields =@Html.Raw(Json.Encode(Model.DocumentFields)); 
$("#datatable-search-input-container-rowone-coltwo").on("click", "#add-row", function (e) {
    var htmlElements = "<div class='col-sm-10 row'>";
    htmlElements = htmlElements + "<div class='col-sm-3 search-spacing'>";
    htmlElements = htmlElements + "<label>Document Categories</label>";
    htmlElements = htmlElements + "<select class='form-control' name='CategoryId[]'>;
    htmlElements += "<option>Select Category</option>";
    $.each(modelCategories, function(i,v){
       htmlElements += `<option value="${v.CategoryId}">${v.CategoryName}</option>`
    });

    htmlElements = htmlElements + "</select>";
    htmlElements = htmlElements + "<label>Document Fields</label>";
    htmlElements = htmlElements + "<select class='form-control' name='FieldId[]'>;
    htmlElements += "<option>Select Document Fields</option>";
    $.each(modelCategories, function(i,v){
       htmlElements += `<option value="${v.FieldId}">${v.FieldNameName}</option>`
    });
    htmlElements = htmlElements + "</select>";
    htmlElements = htmlElements + "</div>";
    htmlElements = htmlElements + "</div>";
    $(htmlElements).appendTo("#datatable-search-input-container-rowone-colone-sub");
    return false;
});

Answer 2

ASP.NET Core MVC標記幫助程序的行為類似於@Html.DropDownListFor()幫助程序，它們@Html.DropDownListFor()現在服務器端，應將其視為asp-for服務器端屬性。 您需要使用包含要追加的元素的局部視圖，並伴隨一個控制器操作方法來返回它，如下例所示：

SelectPartialView.cshtml

@model App.Data.ViewModels.FilterDocumentsViewModel

<div class='col-sm-10 row'>
   <div class='col-sm-3 search-spacing'>
       <label>Document Categories</label>
       <select class='form-control category' asp-for='CategoryId' asp-items='@Model.Categories'>Select Category</select>
       <label>Document Fields</label>
       <select class='form-control field' asp-for='FieldId' asp-items='@Model.DocumentFields'>Select Document Fields</select>
   </div>
</div>

控制器動作

public IActionResult GetSelectList()
{
    // do something
    return PartialView("SelectPartialView");
}

然后使用AJAX回調將部分視圖元素附加到目標元素中：

$("#datatable-search-input-container-rowone-coltwo").on("click", "#add-row", function (e) {
    $.get('@Url.Action("GetSelectList", "ControllerName")', function (result) {
        $("#datatable-search-input-container-rowone-colone-sub").append(result);
    });
});

關於級聯的<select>標記幫助器，您需要在兩個下拉列表中定義class選擇器，並使用AJAX填充選項列表：

$('.category').on('change', function() {
    $.ajax({
       type: 'GET',
       url: '@Url.Action("GetFields", "ControllerName")',
       data: { CategoryId: $(this).val() },
       success: function (result) {
           $('.field').empty();
           $.each(result, function (i, item) {
               // replace 'item.Value' and 'item.Text' from corresponding list properties into model class
               $('.field').append('<option value="' + item.Value + '"> ' + item.Text + ' </option>');
           });
       },
       error: function (xhr, status, err) {
           // error handling
       }
    });
});

控制器動作

public IActionResult GetFields(int CategoryId)
{
    // populate SelectListItem here
    return new JsonResult(list);
}

級聯<select>元素的另一個示例可以在這里找到：

ASP.NET MVC核心級聯DropDownList