为构建轮询 Microsoft.VisualStudio.Services.Client 时出现 NullReferenceException

Question

我正在尝试实现一个简单的轮询服务，该服务查询我们的 TFS 实例以获取构建结果（最终这将显示在办公室的构建监视器上）。根据示例 here，我进行了以下尝试：

var uri = new Uri("http://tfs:8080/tfs/defaultcollection");
var connection = new VssConnection(uri, new VssClientCredentials());
var client = connection.GetClient<BuildHttpClient>();

var builds = await client.GetBuildsAsync(
    project: "OurProject",
    maxBuildsPerDefinition: 1,
    type: DefinitionType.Build);

但最后一条语句在客户端库的某个深处抛出 NullReferenceException（底部的完整堆栈跟踪）。

我已经尝试了以下方法，它确实有效，但当然它没有为我提供我正在寻找的信息:)

var client = connection.GetClient<WorkItemTrackingHttpClient>();
var workItems = await client.GetWorkItemsAsync(ids: new List<int> { 7000, 7005});

我是不是对如何查询构建有根本性的误解？如何避免此异常？

更新：不仅仅是我！

我刚刚发现这个错误不是（仅）在客户端产生的；它也在服务器端！对以下 url 的 GET 请求：

http://tfs:8080/tfs/defaultCollection/OurProject/_apis/build/builds?api-version=2.0&maxBuildsPerDefinition=1&type=build

产生一个 500 Internal Server Error 响应，内容如下：

{
  "$id": "1",
  "innerException": null,
  "message": "Object reference not set to an instance of an object.",
  "typeName": "System.NullReferenceException, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089",
  "typeKey": "NullReferenceException",
  "errorCode": 0,
  "eventId": 0
}

遇到这种情况，我该如何排查？我应该 ask/tell 作为运行我们 TFS 服务器的运维人员做什么？我们在寻找什么？

（客户端）异常的堆栈跟踪：

Unhandled Exception: System.AggregateException: One or more errors occurred. 
---> Microsoft.VisualStudio.Services.WebApi.VssServiceResponseException: Object reference not set to an instance of an object.
---> System.NullReferenceException: Object reference not set to an instance of an object.
   --- End of inner exception stack trace ---
   at Microsoft.VisualStudio.Services.WebApi.VssHttpClientBase.HandleResponse(HttpResponseMessage response)
   at Microsoft.VisualStudio.Services.WebApi.VssHttpClientBase.SendAsync>d__49.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.VisualStudio.Services.WebApi.VssHttpClientBase.<SendAsync>d__47`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.VisualStudio.Services.WebApi.VssHttpClientBase.SendAsync>d__53`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.VisualStudio.Services.WebApi.VssHttpClientBase.<SendAsync>d__52`1.MoveNext()
   --- End of inner exception stack trace ---
   at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions)
   at System.Threading.Tasks.Task`1.GetResultCore(Boolean waitCompletionNotification)
   at System.Threading.Tasks.Task`1.get_Result()
   at ConsoleApplication1.Program.Work() in c:\users\tly01\documents\visual studio 2015\Projects\ConsoleApplication1\ConsoleApplication1\Program.cs:line 32
   at ConsoleApplication1.Program.Main(String[] args) in c:\users\tly01\documents\visual studio 2015\Projects\ConsoleApplication1\ConsoleApplication1\Program.cs:line 20

Answer 1

我发现了错误。简短回答，RTFM :)

事实证明，maxBuildsPerDefinition参数只有在同时指定了definitions的情况下才有效。如果只给前者，服务器returns500.

（你可能会争辩说 401 Bad Request 会是更好的回应，但至少现在我知道该怎么做了。）

我的解决方法是改为在客户端进行过滤；我得到所有项目的所有构建，然后按定义和 select 最新的分组：

var builds = await client
    .GetBuildsAsync(
        project: "OurProject",
        type: DefinitionType.Build).Result
    .GroupBy(build => build.Definition.Id)
    .Select(g => g
        .OrderByDescending(build.FinishTime ?? build.StartTime ?? DateTime.MinValue)
        .First());

为构建轮询 Microsoft.VisualStudio.Services.Client 时出现 NullReferenceException

NullReferenceException when polling Microsoft.VisualStudio.Services.Client for builds

c#

tfs

tfs-2015

更新：不仅仅是我！