Question

我正在尝试使用MVC6 Tag Helpers创建CountryCode和CountryName的下拉列表，以便用户在注册后可以选择他们的国家/地区。到目前为止，视图的相关部分看起来像这样

    <form asp-controller="Manage" asp-action="EditCountry" asp-route-returnurl="@ViewData["ReturnUrl"]">
    <div asp-validation-summary="ValidationSummary.ModelOnly" class="text-danger"></div>
    <select asp-for="CountryCode" asp-items="@Model.Countries"></select>

viewmodel的相关部分看起来像这样

    [Display(Name = "Country")]
    public string CountryCode { get; set; }
    public IEnumerable<Country> Countries { get; set; }

国家/地区看起来像这样

    public partial class Country
{
    [Key]
    public string CountryCode { get; set; }
    public string CountryName { get; set; }
    public virtual ICollection<ApplicationUser> Users { get; set; }
}

控制器将国家/地区列表返回到viewmodel

            var model = new IndexViewModel
        {
            CountryCode = user.CountryCode,
            Countries =_customersContext.Countries.OrderBy(c=>c.CountryName),
        };
        return View(model);
    }

但在视图中asp-items="@Model.Countries"有一个波浪形的Cannot convert Country to SelectListItem

此外，我无法在表单中找到如何将CountryCode指定为要返回的属性，将CountryName指定为要显示的属性。

Answer 1

我制作下拉菜单的方式有点类似，只是在我的ViewModel中，我的属性类型为SelectList而不是IEnumerable<>。

public class HomeViewModel
{
    public string CountryCode { get; set; }
    public SelectList CountryList { get; set; }
}

然后在控制器中我获取数据并将其转换为具有两个属性“Id”和“Value”的匿名列表。

反过来，我创建了一个新的SelectList()传递匿名列表，指定dataValueField是什么，dataTextField是什么。

public IActionResult Index()
{
    var countries = _customersContext.Countries.OrderBy(c => c.CountryName).Select(x => new { Id = x.Code, Value = x.Name });

    var model = new HomeViewModel();
    model.CountryList = new SelectList(countries, "Id", "Value");

    return View(model);
}

最后，在视图中：

<div class="form-group">
    <label asp-for="CountryCode" class="col-md-2 control-label"></label>
    <div class="col-md-10">
        <select asp-for="CountryCode" asp-items="@Model.CountryList"></select>
    </div>
</div>

Answer 2

我已经提出了另一种方法，通过扩展Node **nodeArray; nodeArray = malloc(10 * sizeof(Node *)); int i; for (i = 0; i < 10; i++) { nodeArray[i] = malloc(sizeof(Node)); } if (userChoice == 'a') add(&nodeArray, setNumber); void add(Node ***nodeArray, int setNumber) { char userString[5]; printf("Please enter some data: "); scanf("%s", userString); Node *head = *nodeArray[setNumber]; /* head pointer to first element of array (dummy) */ Node *newNode = malloc(sizeof(Node)); /* new node to be added to array */ strncpy(newNode->data, userString, sizeof(newNode->data)); /* copies string entered by the user to data field of new node */ newNode->next = NULL; /* initializes next field of new node to NULL */ Node *tmp = head; /* pointer to head of list */ while (!tmp->next) { tmp->next = newNode; /* inserts new node into array */ tmp = newNode; /* points head to newly added node */ } tmp = head; /* points tmp back to head of list */ printf("List is: "); while (tmp->next) { printf("%s", (tmp->data)); tmp = tmp->next; } }以及一些可以使这种类型的开发更方便的属性。我们讨论了这个问题here。

它基于类<vector xmlns:android="http://schemas.android.com/apk/res/android" android:width="24dp" android:height="24dp" android:viewportWidth="24.0" android:viewportHeight="24.0"> <path android:strokeColor="#FF000000" android:strokeWidth="0.8" android:strokeAlpha="0.5" android:strokeLineJoin="round" android:strokeLineCap="round" android:strokeMiterLimit="1" android:pathData="M12,22c1.1,0 2,-0.9 2,-2h-4c0,1.1 0.89,2 2,2zM18,16v-5c0,-3.07 -1.64,-5.64 -4.5,-6.32L13.5,4c0,-0.83 -0.67,-1.5 -1.5,-1.5s-1.5,0.67 -1.5,1.5v0.68C7.63,5.36 6,7.92 6,11v5l-2,2v1h16v-1l-2,-2z"/> </vector>，它包含项目列表，分别显示文本和值字段的属性。然后在视图中一个简单的类型

<ImageView android:id="@+id/ivNotification" android:layout_width="@dimen/navigation_icon_size" android:layout_height="@dimen/navigation_icon_size" android:scaleType="fitXY" android:src="@drawable/vector_icon_notification"/>。

国家描述符只是GradientDrawable gdFavourite = (GradientDrawable) ivFavourite.getDrawable(); gdFavourite.setStroke(1, colorPrimary); gdFavourite.setColor(colorPrimary); tvFavourite.setTextColor(colorPrimary);。这可以通过利用`nameof-operator

的强大功能来避免魔术字符串

MVC6国家下拉列表

2 个答案: