2个Linq查询可以并行运行吗？答案

【问题标题】：Can 2 Linq Queries be run parallel?2个Linq查询可以并行运行吗？
【发布时间】：2018-08-06 16:30:32
【问题描述】：

我有 2 个 Linq 查询，第一个 Linq 查询返回 1148 条记录，第二个返回 6667 条记录。他们需要 8 分钟的时间来执行。有什么方法可以让它们在并行运行时更快？

var productbacklogworkitem =
               (from w in workItemcollectionList where w.Type.Name == "Product Backlog Item" select new {
                   Id = w.Id,
                   Name = w.Title,
                   FID = (w.WorkItemLinks.Count > 0) ? ((w.WorkItemLinks[0].LinkTypeEnd.Name.ToString() != "Child") ? w.WorkItemLinks[0].TargetId : 0) : 0,
                   Type = w.Type.Name,
                   State =w.State,
                   priorty = Convert.ToInt32(w.Fields["Priority"].Value),
                   Size = Convert.ToInt32(w.Fields["Effort"].Value),
                   StoryPoints = Convert.ToInt32(w.Fields["Story Points"].Value),
                   DoneStatus = w.Fields["Done Status"].Value.ToString(),
                   StoryOwner = w.Fields["Story Owner"].Value.ToString(),
                   Assignedto = w.Fields["Assigned To"].Value.ToString(),
                   StoryAuthor = w.Fields["Story Author"].Value.ToString(),
                   IterationPath = w.IterationPath
               }).ToList();
            var taskbugsworkitem =
             (from w in workItemcollectionList where (w.Type.Name == "Task" || w.Type.Name == "Bug") && (w.WorkItemLinks.Count > 0)   select new {
                 Id = w.Id,
                 Name = w.Title,
                 Type = w.Type.Name,
                 Storyid =  w.WorkItemLinks[0].TargetId,
                 status = w.State,
                 IterationPath = w.IterationPath,
                 Assignedto = w.Fields["Assigned To"].Value.ToString(),
                 priorty = Convert.ToInt32(w.Fields["Priority"].Value),
                 effort = Convert.ToInt32(w.Fields["effort"].Value),
                 Completed = (w.Type.Name== "Task") ? Convert.ToInt32(w.Fields["Completed"].Value):0
             }) .ToList();

【问题讨论】：

System.Threading.Tasks.Parallel.ForEach search for this 将您的代码调整为上述格式。这对这个问题很有用。
为什么要通过一个查询从数据库中提取约 7000 条记录？
碰巧有7k条记录@xxbbcc
@AkhilJain 您需要一次性提取所有数据吗？即使并行，它也不会突然大幅加速，除了随着数据的增长它可能会越来越慢。似乎这是实现一些分页的好地方，所以每次从数据库中加载 X 行。
@AkhilJain 你能说明workItemcollectionList 是什么以及其中的项目类别吗？你可以省略一些东西，只要你有一个mcve 的例子。 Anupam Singh 的答案似乎不错，但可能由于缺少上下文而失败。

标签： c# multithreading linq tfs-workitem plinq

【解决方案1】：

您也可以使用Task 进行两个并行查询。

Task<ResultClass1> t1 = Task<ResultClass1>.Run(() =>
    {
        var productbacklogworkitem =
        (from w in workItemcollectionList
         where w.Type.Name == "Product Backlog Item"
         select new ResultClass1
        {
            Id = w.Id,
            Name = w.Title,
            FID = (w.WorkItemLinks.Count > 0) ? ((w.WorkItemLinks[0].LinkTypeEnd.Name.ToString() != "Child") ? w.WorkItemLinks[0].TargetId : 0) : 0,
            Type = w.Type.Name,
            State = w.State,
            priorty = Convert.ToInt32(w.Fields["Priority"].Value),
            Size = Convert.ToInt32(w.Fields["Effort"].Value),
            StoryPoints = Convert.ToInt32(w.Fields["Story Points"].Value),
            DoneStatus = w.Fields["Done Status"].Value.ToString(),
            StoryOwner = w.Fields["Story Owner"].Value.ToString(),
            Assignedto = w.Fields["Assigned To"].Value.ToString(),
            StoryAuthor = w.Fields["Story Author"].Value.ToString(),
            IterationPath = w.IterationPath
        }).ToList();

        return ResultClass1;
    });

Task<ResultClass2> t2 = Task<ResultClass2>.Run(() =>
    {
        var taskbugsworkitem =
            (from w in workItemcollectionList
            where (w.Type.Name == "Task" || w.Type.Name == "Bug") && (w.WorkItemLinks.Count > 0)
             select new ResultClass2
            {
                Id = w.Id,
                Name = w.Title,
                Type = w.Type.Name,
                Storyid = w.WorkItemLinks[0].TargetId,
                status = w.State,
                IterationPath = w.IterationPath,
                Assignedto = w.Fields["Assigned To"].Value.ToString(),
                priorty = Convert.ToInt32(w.Fields["Priority"].Value),
                effort = Convert.ToInt32(w.Fields["effort"].Value),
                Completed = (w.Type.Name == "Task") ? Convert.ToInt32(w.Fields["Completed"].Value) : 0
            }).ToList();

        return taskbugsworkitem;
    });

Task.WaitAll(t1, t2);

// get results from these
t1.Result;
t2.Result;

【讨论】：

【解决方案2】：

您可以尝试 PLINQ，在实体上使用 AsParallel()

var productbacklogworkitem =
               (from w in workItemcollectionList.AsParallel() where w.Type.Name == "Product Backlog Item" select new {
                   Id = w.Id,
                   Name = w.Title,
                   FID = (w.WorkItemLinks.Count > 0) ? ((w.WorkItemLinks[0].LinkTypeEnd.Name.ToString() != "Child") ? w.WorkItemLinks[0].TargetId : 0) : 0,
                   Type = w.Type.Name,
                   State =w.State,
                   priorty = Convert.ToInt32(w.Fields["Priority"].Value),
                   Size = Convert.ToInt32(w.Fields["Effort"].Value),
                   StoryPoints = Convert.ToInt32(w.Fields["Story Points"].Value),
                   DoneStatus = w.Fields["Done Status"].Value.ToString(),
                   StoryOwner = w.Fields["Story Owner"].Value.ToString(),
                   Assignedto = w.Fields["Assigned To"].Value.ToString(),
                   StoryAuthor = w.Fields["Story Author"].Value.ToString(),
                   IterationPath = w.IterationPath
               }).ToList();
            var taskbugsworkitem =
             (from w in workItemcollectionList.AsParallel() where (w.Type.Name == "Task" || w.Type.Name == "Bug") && (w.WorkItemLinks.Count > 0)   select new {
                 Id = w.Id,
                 Name = w.Title,
                 Type = w.Type.Name,
                 Storyid =  w.WorkItemLinks[0].TargetId,
                 status = w.State,
                 IterationPath = w.IterationPath,
                 Assignedto = w.Fields["Assigned To"].Value.ToString(),
                 priorty = Convert.ToInt32(w.Fields["Priority"].Value),
                 effort = Convert.ToInt32(w.Fields["effort"].Value),
                 Completed = (w.Type.Name== "Task") ? Convert.ToInt32(w.Fields["Completed"].Value):0
             }) .ToList();

【讨论】：

获取错误集合已修改枚举操作可能无法执行
抱歉，不确定这个问题。但您可以参考链接进行探索。