我的标记助手下拉选择将无法在.NET Core中正确呈现

如何解决我的标记助手下拉选择将无法在.NET Core中正确呈现

<div class="form-group">
      <label asp-for="roles" class="control-label"></label>
        <select asp-for="roles" class="custom-select" asp-items="@(new Select List(ViewBag.Roles))">
                    <option value="">Assign Role</option>
                </select>
</div>

<div class="form-group row">
        <label class="col-sm-2 col-form-label">State</label>
         <div class="col-sm-10">
            <select asp-for="roles" class="form-control custom-select"  style="height:20px" asp-items="@(new Select List(ViewBag.Roles,"Id","Name"))">
            <option value="">Large select</option>
         </select>
         </div>
</div>

my drop down in not responsive any help 
how to make drop down responsive 

解决方法

ViewBag.Roles的值可能分配不正确。这是一个例子。

在Index.cshtml

@{

  ViewBag.Roles = new List<MyModel>
  {
    new MyModel{Id=1,Name="thisname"},new MyModel{Id=2,Name="thisname2"},};
}
<div class="form-group row">
<label class="col-sm-2 col-form-label">State</label>
<div class="col-sm-10">
    <select asp-for="roles" class="form-control custom-select" style="height:20px" 
        asp-items="@(new SelectList(ViewBag.Roles,"Id","Name"))">
        <option value="">Large select</option>
    </select>
</div>

这是模型。

public class MyModel
{
    public int Id { get; set; }
    public string Name { get; set; }
}

结果。