Question

我试图查询表中的行数，然后将其返回到我的Controller Action。我使用Dapper作为我的Micro-ORM，并且似乎在尝试实现这一目标时遇到了一些问题。

服务方法

public Task<int> GetPostCount()
{
    using (var connection = new SqlConnection(configuration.GetConnectionString("DefaultConnection")))
    {
        return connection.QuerySingleAsync<int>(SqlQueries.Post.SelectPostCount);
    }
}

控制器操作

[HttpGet("Posts/{page:int?}")]
public async Task<IActionResult> Posts(int page)
{
    IEnumerable<PostHighlightViewModel> posts = await this.postService.GetAllPosts(postsPerPage, page < 1 ? 1 : page);
    if (posts.Count() == 0)
    {
        // BOOM goes the dynamite - right here.
        int numberOfPosts = await this.postService.GetPostCount();
        int pageToFetch = numberOfPosts / postsPerPage;
        posts = await this.postService.GetAllPosts(postsPerPage, pageToFetch);
    }

    return View("Index", posts);
}

我执行的Sql是

SELECT COUNT(*) FROM POSTS

当我执行查询时，我收到以下异常

申请已开始。按Ctrl + C关闭。失败：Microsoft.AspNetCore.Server.Kestrel，Version = 1.0.0.0，Culture = neutral，PublicKeyToken = adb9793829ddae60 [13] 连接ID＆＃34; 0HKSQRDBQRA9E＆＃34;：应用程序抛出了未处理的异常。 System.InvalidOperationException：无效的操作。连接已关闭。在System.Data.SqlClient.SqlCommand。＆lt;＆gt; c.b__110_0（任务1 result) at System.Threading.Tasks.ContinuationResultTaskFromResultTask 2.InnerInvoke（）在System.Threading.Tasks.Task.Execute（） ---从抛出异常的先前位置开始的堆栈跟踪结束--- 在System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess（任务任务）在System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification（任务任务）在Dapper.SqlMapper.d__24 1.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Runtime.CompilerServices.TaskAwaiter 1.GetResult（）在BlogWeb.Controllers.PostController.d__4.MoveNext（）在C：\ Users \ johnathonsullinger \ Source \ VSTS \ Blog.Core \ Source \ BlogWeb \ Controllers \ PostController.cs：第32行 ---从抛出异常的先前位置开始的堆栈跟踪结束--- 在System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess（任务任务）在System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification（任务任务）在Microsoft.AspNetCore.Mvc.Internal.ObjectMethodExecutor.d__24 1.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.<InvokeActionAsync>d__6.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.AspNetCore.Mvc.Internal.FilterActionInvoker.<InvokeActionFilterAsync>d__41.MoveNext() --- End of stack trace from previous location where exception was thrown --- at Microsoft.AspNetCore.Mvc.Internal.FilterActionInvoker.<InvokeAsync>d__32.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.AspNetCore.Mvc.Internal.MvcRouteHandler.<InvokeActionAsync>d__8.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.AspNetCore.Builder.RouterMiddleware.<Invoke>d__4.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.AspNetCore.Hosting.Internal.RequestServicesContainerMiddleware.<Invoke>d__3.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.AspNetCore.Server.Kestrel.Http.Frame 1.d__2.MoveNext（）

为了试图找出发生的事情，我离开这里并不多。我可以毫无问题地进行其他查询，但尝试查询记录计数似乎是一个问题。

我已尝试使用QueryFirstOrDefaultAsync和QuerySingleAsync。我应该不使用QueryAsync系列方法吗？

Answer 1

当执行从using块返回时，将处理连接，因此在async操作可以结束之前关闭连接。

您可以考虑在ContinueWith中关闭连接，以确保在async操作完成后关闭。

或者，我认为您可以在异步调用中使用await关键字。

SELECT COUNT（*）在查询时抛出异常

服务方法

控制器操作

1 个答案: