如何检索列表变量的值（按

Question

我正在尝试按项目ID分组，以便我可以返回总和，但是当我尝试使用First（）返回字段的值时，它只返回一个值。ASP.net c#项目尝试返回字段的总和时，我使用LINQ的代码返回正确的数字，但我似乎无法返回相应的字符串字段。我尝试按2个字段分组，但这会返回太多记录。public class JobsByDrivetime{private string pid;private double jobMinutes;private string jobEventType;public JobsByDrivetime(string pid, double jobMinutes,string jobEventType){    this.pid = pid;    this.jobMinutes = jobMinutes;    this.jobEventType = jobEventType;}public string Pid{    get { return pid; }    set { pid = value; }}public double JobMinutes{    get { return jobMinutes; }    set { jobMinutes = value; }}public string JobEventType{    get { return jobEventType; }    set { jobEventType = value; }}}List<JobsByDrivetime> ProjectbyDrivetime = new List<JobsByDrivetime>();ProjectbyDrivetime.Add(new JobsByDrivetime("0186975-0001", 439, "HR"));ProjectbyDrivetime.Add(new JobsByDrivetime("0186975-0001", 100, "HR"));ProjectbyDrivetime.Add(new JobsByDrivetime("0186975-0001", 180, "JR"));var projectBydrivetimeList = ProjectbyDrivetime.GroupBy(v => v.Pid) //(c => new { Pid = c.Pid, ProjectType = c.JobEventType }).Select(g => new{    Pid = g.Key,    ProjectMinutes = g.Sum(x => x.JobMinutes),    ProjectType=g.Select(x=> x.JobEventType).First()}).ToList();foreach (var D in projectBydrivetimeList){    shiftSummary.Add("<tr><td>" + D.Pid + "</td><td>" + D.ProjectType + "</td><td>" + D.ProjectMinutes + "</td></tr>");}输出0186975-0001 HR 5390186975-0001 HR 180它（按项目类型）正确分组项目分钟，但它仅显示2个项目类型中的一种。我希望D.ProjectType在第一个是HR，在第二个是JR。我明白这是因为我正在使用First（）。

Answer 1

我希望我正确地理解了您的要求。你几乎按照你的想法来按Pid和ProjectType进行分组。

var projectBydrivetimeList = ProjectbyDrivetime
                             .GroupBy(v => new {v.Pid,v.JobEventType}) 
                             .Select(g => new
                             {
                               Pid = g.Key.Pid,
                               ProjectMinutes = g.Sum(x => x.JobMinutes),
                               ProjectType=g.Select(x=> x.JobEventType).First()
                              }).ToList();

示例输出

更新

根据您的评论，另一个示例输入

输出