问题描述
根据 this 教程,我的代码有问题。 我尝试制作角色列表并从特定角色中添加或删除用户。
这是我在控制器中的代码:
[HttpPost]
public async Task<IActionResult> EditUsersInRole(List<UserRoleviewmodel> model,string roleId)
{
ViewBag.roleId = roleId;
var role = await roleManager.FindByIdAsync(roleId);
if (role == null)
{
ViewBag.ErrorMessage = $"Role with ID = {roleId} cannot be found.";
return View("NotFound");
}
for (int i = 0; i < model.Count; i++)
{
var user = await userManager.FindByIdAsync(model[i].UserId);
IdentityResult result = null;
if (model[i].IsSelected && !(await userManager.IsInRoleAsync(user,role.Name)))
{
result = await userManager.AddToRoleAsync(user,role.Name);
}
else if (!model[i].IsSelected && await userManager.IsInRoleAsync(user,role.Name))
{
result = await userManager.RemoveFromroleAsync(user,role.Name);
}
else
{
continue;
}
if (result.Succeeded)
{
if (i < (model.Count - 1))
continue;
else
return RedirectToAction("EditRole",new { Id = roleId });
}
}
return RedirectToAction("EditRole",new { Id = roleId });
}
EditUsersInRole 查看代码:
@model List<collector_forum.viewmodels.UserRoleviewmodel>
@{
var roleId = ViewBag.roleId;
}
<form method="post">
<div class="card">
<div class="card-header">
<h2>Add or remove users from this role</h2>
</div>
<div class="card-body">
@for (int i = 0; i < Model.Count; i++)
{
<div class="form-check m-1">
<input asp-for="@Model[i].IsSelected" class="form-check-input" />
<label class="form-check-label" asp-for="@Model[i].IsSelected">
@Model[i].UserName
</label>
</div>
}
</div>
<div class="card-footer">
<input type="submit" value="Update" class="btn btn-primary" style="width: auto;" />
<a asp-action="EditRole" asp-route-id="@roleId" class="btn btn-primary" style="width: auto;">Cancel</a>
</div>
</div>
</form>
和视图模型:
namespace collector_forum.viewmodels
{
public class UserRoleviewmodel
{
public string UserId { get; set; }
public string UserName { get; set; }
public bool IsSelected { get; set; }
}
}
然后我得到这个错误:
ArgumentNullException:值不能为空。 (参数'用户')
我现在很无助
请帮帮我。
//编辑。
发帖前的 Html 视图 - screenshot
Chrome 开发者工具 -> 网络标签 before 点击“更新”
然后点击“更新”view
解决方法
您忘记发送 UserId 而您得到的是一个空用户
<div class="card-body">
@for (int i = 0; i < Model.Count; i++)
{
<div class="form-check m-1">
<input type="hidden" asp-for="@Model[i].UserId" />
<input asp-for="@Model[i].IsSelected" class="form-check-input" />
<label class="form-check-label" asp-for="@Model[i].IsSelected">
@Model[i].UserName
</label>
</div>
}
</div>