Question

我是asp.net MVC的初学者。我在要在Get方法中更新的模型中创建了一个List属性。我使用ViewBag将其绑定到视图中的下拉列表。我正在尝试在post方法中获取下拉列表的选定值。

下面是方法。

//UserRole Model

public UserRole()
{
     UsersNotInRole = new List<string>();
}
    public string Id { get; set; }     
    public List<string> UsersNotInRole { get; set; }
}

在UsersInRole中更新列表[HttpGet]操作方法：

[HttpGet]
public async Task<IActionResult> UsersInRole(string roleId, string roleName)
{

     //Finds the role associated with the specified roleId if any.
      var role = await roleManager.FindByIdAsync(roleId);


            //initialize the model properties
       var model = new UserRole
       {
           Id = role.Id
       };
//add the users not in the role to the UsersNotInRole property in model
            foreach (var user in userManager.Users)
            {
                if (!await userManager.IsInRoleAsync(user, role.Name))
                {
                   model.UsersNotInRole.Add(user.UserName);

                }
            }
//Binding list to the drop-down list in view using ViewBag
ViewData["UsersNotInRole"] = new SelectList(model.UsersNotInRole);
return View(model);
}

AddUserToRole POST方法：

[HttpPost]
public async Task<IActionResult> AddUserToRole(string roleId, string userName) //userName?? selected from UserNotInRole list
{
  var user = await userManager.FindByNameAsync(userName);
            if (user == null)
            {
                TempData["message"] = $"User selected cannot be found";
                return RedirectToAction("UsersInRole", new { roleId = role.Id.ToString(), roleName = role.Name.ToString() });
            }
            // Add user to role
            IdentityResult addResult = await userManager.AddToRoleAsync(user, userName);

return RedirectToAction("UsersInRole");
}

//查看

@model UserRole
@{
    ViewData["Title"] = $"Users In Role";
}

<h1>@ViewData["Title"]</h1>

        <form method="post">
            <div asp-validation-summary="ModelOnly" class="text-danger"></div>
            <div class="form-group row">
                <label class="control-label">Users not in role: </label>
                <select asp-for="UsersNotInRole" class="form-control" asp- 
                     items="ViewBag.UsersNotInRole"></select>
                <button type="submit" asp-action="AddUserToRole" asp-route-roleId="@Model.Id" class="btn 
                  btn-primary"> Add to Role</button>
            </div>
        </form>

Answer 1

您可以使用代替选择标签的方式来使用：

@Html.DropDownListFor(m => m.Id, ViewData["UsersNotInRole"] as SelectList)

Answer 2

给表单标签一个动作和控制器地址，然后输入一个带有提交类型（或按钮）的输入，然后将模型作为输入传递给后动作。当用户单击提交输入（或按钮）时，包含用户数据的模型将返回到发布操作，下拉列表的ID以及模型的其他属性也将返回。

<form method="post" action="/controller/action">
    <button type="submit" class="btn btn-primary"> Add to Role</button>  
</form>

并显示下拉菜单，可以在视图中使用@ Html.DropDown（）。如果您不知道该如何使用，请使用下面的链接。

https://www.tutorialsteacher.com/mvc/htmlhelper-dropdownlist-dropdownlistfor

，您的操作信息应为：

[HttpPost]
public async Task<IActionResult> AddUserToRole(UserRole model)
{
    return RedirectToAction("UsersInRole");
}

如何在Post方法MVC中获取DropDownList的选定值

2 个答案: