c# - 一个 Action 可以授权给定用户/角色以外的所有人吗？

Question

使用 [Authorize] 属性可以轻松地将操作设置为仅由特定用户或角色允许。例如。

[Authorize(Roles = "Administrator")]
public ActionResult Index()
{
  ...

但是，当我想要反转时，我遇到了一个问题。有没有一种方法可以使用 MVC 框架功能允许所有经过身份验证的用户按名称或角色指定的用户除外？

所需的用法类似于:

[DoNotAuthorize(Roles = "RestrictedUser")]
public ActionResult Index()
{
  ...

Answer 1

一个相当简单的解决方案是派生自 AuthorizeAttribute 类并覆盖其 AuthorizeCore 方法，交换其真/假逻辑。

/// <summary>
/// Authorizes any authenticated user *except* those who match the provided Users or Roles.
/// </summary>
public class DoNotAuthorizeAttribute : AuthorizeAttribute
{
    /// <summary>
    /// This is effectively a copy of the MVC source for AuthorizeCore with true/false logic swapped.
    /// </summary>
    /// <param name="httpContext">The HTTP context, which encapsulates all HTTP-specific information about an individual HTTP request.</param>
    /// <returns>true if the user is authorized; otherwise, false.</returns>
    protected override bool AuthorizeCore(HttpContextBase httpContext)
    {
        if (httpContext == null)
        {
            throw new ArgumentNullException("httpContext");
        }
        IPrincipal user = httpContext.User;
        if (!user.Identity.IsAuthenticated)
        {
            return false;
        }

        string[] usersSplit = SplitString(Users);
        if ((usersSplit.Length > 0) && usersSplit.Contains<string>(user.Identity.Name, StringComparer.OrdinalIgnoreCase))
        {
            return false;
        }

        string[] rolesSplit = SplitString(Roles);
        if ((rolesSplit.Length > 0) && rolesSplit.Any<string>(new Func<string, bool>(user.IsInRole)))
        {
            return false;
        }

        return true;
    }

    /// <summary>
    /// This is a direct copy of the MVC source for the internal SplitString method.
    /// </summary>
    /// <param name="original">The original string to split.</param>
    /// <returns>An array of strings.</returns>
    internal static string[] SplitString(string original)
    {
        if (string.IsNullOrWhiteSpace(original))
        {
            return new string[0];
        }
        return (from piece in original.Split(new[] { ',' })
                let trimmed = piece.Trim()
                where !string.IsNullOrEmpty(trimmed)
                select trimmed).ToArray<string>();
    }
}