分组时如何检索列表变量的值

Question

我试图按项目ID进行分组，以便可以返回一个总和，但是当我尝试使用First（）返回字段的值时，它仅返回一个值。

ASP.net c＃项目试图返回一个字段的总和，我有使用LINQ返回正确数字的代码，但是我似乎无法返回相应的字符串字段。我尝试按2个字段进行分组，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 539

0186975-0001 HR 180

它正确地对ProjectMinutes进行了分组（按项目类型），但仅显示2个项目类型之一。我期望D.ProjectType在第一个成为HR，在第二个成为JR。我明白这是因为我正在使用First（）。

Answer 1

希望我能正确理解您的要求。出于对Group By Pid和ProjectType的考虑，您已经步入正轨。

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();

样本输出

更新

根据您的评论，另一个示例输入

输出