如何在AuthorizationHandler中获取POST请求参数

public class CustomAuthorizationHandler : AuthorizationHandler<CustomRequirement>
{
    private readonly IHttpContextAccessor _httpContextAccessor;

    public CustomAuthorizationHandler(IHttpContextAccessor httpContextAccessor)
    {
        _httpContextAccessor = httpContextAccessor;
    }

    protected override Task HandleRequirementAsync(AuthorizationHandlerContext context, CustomRequirement requirement)
    {
        var httpContext = _httpContextAccessor.HttpContext;
        var request = httpContext.Request;

        if (request.Method == "POST")
        {
            var username = request.Form["username"];
            var password = request.Form["password"];

            // 进行身份验证逻辑
            // ...

            // 根据业务逻辑判断是否满足授权要求
            if (/* 满足授权要求 */)
            {
                context.Succeed(requirement);
            }
        }

        return Task.CompletedTask;
    }
}