MVC EF6 异步删除

Question

在我的控制器中我有行动

[HttpPost, ActionName("Delete")]
[ValidateAntiForgeryToken]
public async Task<ActionResult> DeleteConfirmed(int id)
{
    clsHost HostDAL = new clsHost();
    vw_Host vw_host = await HostDAL.GetByIdAsync(id);
    string actionStatus = HostDAL.Delete(vw_host);

    TempData["msgHost"] = actionStatus;
    return RedirectToAction("Display");
}

删除方法：

public string Delete(vw_Host host)
{
    ObjectParameter executionStatus = new ObjectParameter("ExecutionStatus", "");

    try
    {
        using (Entities context = new Entities())
        {
            string name = HttpContext.Current.User.Identity.Name.ToString();
            context.sp_Host_Delete(host.ID, HttpContext.Current.User.Identity.Name.ToString(), executionStatus);
            context.SaveChanges();
        }
    }
    catch (Exception ex)
    {
        using (Entities context = new Entities())
        {
            context.sp_LogError(this.GetType().Name.ToString() + "." + System.Reflection.MethodBase.GetCurrentMethod().Name.ToString(), ex.Message, HttpContext.Current.User.Identity.Name);
            context.SaveChanges();
        }

        executionStatus.Value = "Error occured. Please contact to Administrator";
    }

    return executionStatus.Value.ToString();
}

我的问题是，当我使用 Async DeleteConfirmed 操作时，在 Delete 方法中出现错误：

对象引用未设置为对象的实例。

为

HttpContext.Current.User.Identity.Name

另一方面，当我使用同步操作时：

[HttpPost, ActionName("Delete")]
[ValidateAntiForgeryToken]
public ActionResult DeleteConfirmed(int id)
{
    clsHost HostDAL = new clsHost();
    vw_Host vw_host = HostDAL.GetById(id);
    string actionStatus = HostDAL.Delete(vw_host);

    TempData["msgHost"] = actionStatus;
    return RedirectToAction("Display");
}

一切正常，HttpContext.Current.User.Identity.Name 没有返回错误。 仅删除操作会出现此问题。它适用于编辑操作（甚至是异步操作）。

Answer 1

您还可以考虑在调用 async 之前获取用户并将其作为参数传递给 delete 方法。

[HttpPost, ActionName("Delete")]
[ValidateAntiForgeryToken]
public async Task<ActionResult> DeleteConfirmed(int id) {
    var name = "Unknown";
    try {
        name = HttpContext.Current.User.Identity.Name.ToString();
    }catch { }
    clsHost HostDAL = new clsHost();
    vw_Host vw_host = await HostDAL.GetByIdAsync(id);
    string actionStatus = HostDAL.Delete(vw_host, name);

    TempData["msgHost"] = actionStatus;
    return RedirectToAction("Display");
}

重构的删除方法

public string Delete(vw_Host host, string name) {
    ObjectParameter executionStatus = new ObjectParameter("ExecutionStatus", "");

    try {
        using (Entities context = new Entities()) {
            context.sp_Host_Delete(host.ID, name, executionStatus);
            context.SaveChanges();
        }
    } catch (Exception ex) {
        using (Entities context = new Entities()) {
            context.sp_LogError(this.GetType().Name.ToString() + "." + System.Reflection.MethodBase.GetCurrentMethod().Name.ToString(), ex.Message, name);
            context.SaveChanges();
        }

        executionStatus.Value = "Error occured. Please contact to Administrator";
    }

    return executionStatus.Value.ToString();
}