Xamarin.forms CancellationToken源在xamarin表单中不工作

我有5个任务一起运行

        var tasks = new ConcurrentBag<Task>();
        cancellationTokenSource = new CancellationTokenSource();
        var token = cancellationTokenSource.Token;

        Task<InvServiceModel> t1 = GetInventoryLine(cancellationTokenSource.Token);
        tasks.Add(t1);

        Task<ProductServiceModel> t2 = GetProductData(cancellationTokenSource.Token);
        tasks.Add(t2);

        Task<List<InvLineCost>> t3 = GetInvLineCostData(cancellationTokenSource.Token);
        tasks.Add(t3);

        Task<MiscDataMobileServiceModel> t4 = GetMiscellaniousMobileData(cancellationTokenSource.Token);
        tasks.Add(t4);

        Task<RecipeHierarchyModel> t5 = GetRecipeHierarhyData(cancellationTokenSource.Token);
        tasks.Add(t5);

        Task<UnknownInvStorage> t6 = GetUnknownStorageLocationData(cancellationTokenSource.Token);
        tasks.Add(t6);


        try
        {
            await Task.WhenAll(tasks.ToArray());
        }
        catch (AggregateException ae)
        {
            if (ae.InnerExceptions.Any(e => e is TaskCanceledException))
                Console.WriteLine("Task cancelled exception detected");
            else
                throw;
        }
        catch (OperationCanceledException ae)
        {
            Console.WriteLine("Task cancelled exception detected {0}", ae);
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex);
        }
        finally
        {
            cancellationTokenSource.Dispose();
        }

如何取消所有任务？似乎有一些问题

 cancellationToken.ThrowIfCancellationRequested();

未在单个任务方法中调用

服务调用方法示例如下：

    public async Task<InvServiceModel> GetInventoryLineItems(string Restaurantid, string 
      FromDate, CancellationToken cancellationToken)
    {
        InvServiceModel invservicemodel = null;
        HttpResponseMessage responseMessage = null;

        try
        {
            cancellationToken.ThrowIfCancellationRequested();
            var api = RestService.For<IInventoryLineItemsApi>(_httpClient);
            responseMessage = await api.GetInventoryLineItems(Restaurantid, FromDate, cancellationToken).ConfigureAwait(false);
            cancellationToken.ThrowIfCancellationRequested();

            if (responseMessage.StatusCode == System.Net.HttpStatusCode.OK)
            {
               //
            }
            else
            {
                //
                throw serviceException;
            }
        }
        catch (TaskCanceledException ex)
        {
            Console.WriteLine("TaskCanceledException GetInventoryLineItems");
            throw ex;
        }
        catch (Exception ex)
        {
            throw ex;
        }

        return invservicemodel;
    }

public异步任务GetInventoryLineItems（字符串Restaurantid，字符串
FromDate，CancellationToken CancellationToken）
{
InvServiceModel InvServiceModel=null；
HttpResponseMessage responseMessage=null；
尝试
{
cancellationToken.ThrowIfCancellationRequested（）；
var api=RestService.For（_httpClient）；
responseMessage=await api.GetInventoryLineItems（Restaurantid、FromDate、cancellationToken）。ConfigureAwait（false）；
cancellationToken.ThrowIfCancellationRequested（）；
if（responseMessage.StatusCode==System.Net.HttpStatusCode.OK）
{
//
}
其他的
{
//
抛出serviceException；
}
}
捕获（TaskCanceledException ex）
{
控制台.WriteLine（“TaskCanceledException GetInventoryLineItems”）；
掷骰子；
}
捕获（例外情况除外）
{
掷骰子；
}
返回模型；
}

您需要保留对它的引用，以便下次调用处理程序时可以取消上一次搜索。检查。您需要保留对它的引用，以便下次调用处理程序时可以取消上一次搜索。检查。

    public async Task<InvServiceModel> GetInventoryLineItems(string Restaurantid, string 
      FromDate, CancellationToken cancellationToken)
    {
        InvServiceModel invservicemodel = null;
        HttpResponseMessage responseMessage = null;

        try
        {
            cancellationToken.ThrowIfCancellationRequested();
            var api = RestService.For<IInventoryLineItemsApi>(_httpClient);
            responseMessage = await api.GetInventoryLineItems(Restaurantid, FromDate, cancellationToken).ConfigureAwait(false);
            cancellationToken.ThrowIfCancellationRequested();

            if (responseMessage.StatusCode == System.Net.HttpStatusCode.OK)
            {
               //
            }
            else
            {
                //
                throw serviceException;
            }
        }
        catch (TaskCanceledException ex)
        {
            Console.WriteLine("TaskCanceledException GetInventoryLineItems");
            throw ex;
        }
        catch (Exception ex)
        {
            throw ex;
        }

        return invservicemodel;
    }