.NET Core< select>具有默认值？ [英] .NET Core <select> With Default Value?

问题描述

我的目标是生成具有特定选择值的< select> 下拉列表（< option> ）预选，因此最终的 HTML 应该如下所示：

My goal is to generate a <select> dropdown with a certain select value (<option>) pre-selected, so the finalized HTML should look like this:

<select>
  <option value = "1">Option1</option>
  <option value = "2" selected>Option2</option>
  <option value = "3">Option3</option>
</select>

请注意，值为2的选项已选择 属性，表示它将在单击下拉菜单之前显示。我无法（并且正在尝试）使用.NET Core Tag Helpers来实现这一目标。

Note that the option with a value of 2 has a selected attribute, indicating that it will show before the dropdown is clicked. I cannot (and am trying to) achieve this using .NET Core Tag Helpers.

这是我的模型（我认为您可以放心地忽略细节）：

This is my model (I think you can safely ignore the details):

public class ReportViewModel
{
  [Display(Name = "Pick a form")]
  public IEnumerable<Form> AvailableForms { get; set; }

  public Form SelectedForm { get; set; }

  public List<ReportData> FormResponses { get; set; }
}

请注意，表格对象上仅具有 Id 和 Name 属性。

Note that the Form object there just has Id and Name properties on it.

这是我的选择语句：

<label asp-for="SelectedForm.Name" class="form-control-label font-weight-bold"></label>
<select asp-for="SelectedForm.Name"
        class="form-control"
        onchange ="onFormSelected(this.value)"
        asp-items="@(new SelectList(Model.AvailableForms, "Id", "Name"))">
</select>

我没有在 Microsoft指南
或在关于该主题的博客中

推荐答案

基本上，您需要将选择设置为使用 SelectedForm.Id 属性，然后指定要在控制器中选择的表单的值。我不得不稍微更新一下您的代码，但这对我有用-

Basically you need to is set the select to use the SelectedForm.Id property, then specify the value of the form to be selected in your controller. I had to update your code a little but this works for me -

<label asp-for="SelectedForm" class="form-control-label font-weight-bold"></label>
<select asp-for="SelectedForm.Id"
        class="form-control"
        onchange ="onFormSelected(this.value)"
        asp-items="@(new SelectList(Model.AvailableForms, "Id", "Name"))">
</select>

然后在您的控制器中

var vm = new ReportViewModel()
{
    AvailableForms = new List<Form>()
};

var form2 = new Form() { Id = 2, Name = "Bar" };
(vm.AvailableForms as List<Form>).Add(new Form() { Id = 1, Name = "Foo" });
(vm.AvailableForms as List<Form>).Add(form2);
(vm.AvailableForms as List<Form>).Add(new Form() { Id = 3, Name = "Baz" });

vm.SelectedForm = form2;

return View(vm);

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