List 将项目添加到现有列表mvc5

（我是一名新开发人员）我有一个列表，我把它放在一个viewBag中，以便在我的视图中进行下拉，我想在这个列表中添加3个元素，以便我们可以在下拉列表的末尾看到它们。我为员工制作了一份时间表，我有一份员工在一周内工作项目的下拉列表，如果员工休假而不是工作，我想在下拉列表的末尾添加3个选项“空缺”、“计划外缺勤”、“计划内缺勤”

var projectAssignment = (from pa in db.ProjectAssignment
                                     join p in db.Projects on pa.ProjectId equals p.ID
                                     where pa.EmployeeId == EmployeeId && pa.StartDate !=null && (pa.EndDate == null || pa.EndDate >= DateTime.Now)
                                     select new ProjectTimesheetList
                                     {
                                         ProjectName = p.ProjectName,
                                         ProjectId = pa.ProjectId
                                     });

            List<ProjectTimesheetList> projectAssignments = projectAssignment.ToList();

            projectAssignments.Add(new ProjectTimesheetList
            {
                ProjectName = "Vacancy",
                ProjectId = -1,
            });

            projectAssignments.Add(new ProjectTimesheetList
            {
                ProjectName = "Unplanned Absence",
                ProjectId = -2,
            });

            projectAssignments.Add(new ProjectTimesheetList
            {
                ProjectName = "Planned Absence",
                ProjectId = -3,
            });

            ViewBag.ProjectTimeSHeet = projectAssignments;

这是我对项目的要求：

var projectAssignment = (from pa in db.ProjectAssignment
                                     join p in db.Projects on pa.ProjectId equals p.ID
                                     where pa.EmployeeId == EmployeeId && pa.StartDate !=null && (pa.EndDate == null || pa.EndDate >= DateTime.Now)
                                     select new ProjectTimesheetList
                                     {
                                         ProjectName = p.ProjectName,
                                         ProjectId = pa.ProjectId
                                     });
ViewBag.ProjectTimeSHeet = projectAssignment;

var projectAssignment = (from pa in db.ProjectAssignment
                                     join p in db.Projects on pa.ProjectId equals p.ID
                                     where pa.EmployeeId == EmployeeId && pa.StartDate !=null && (pa.EndDate == null || pa.EndDate >= DateTime.Now)
                                     select new ProjectTimesheetList
                                     {
                                         ProjectName = p.ProjectName,
                                         ProjectId = pa.ProjectId
                                     });

            List<ProjectTimesheetList> projectAssignments = projectAssignment.ToList();

            projectAssignments.Add(new ProjectTimesheetList
            {
                ProjectName = "Vacancy",
                ProjectId = -1,
            });

            projectAssignments.Add(new ProjectTimesheetList
            {
                ProjectName = "Unplanned Absence",
                ProjectId = -2,
            });

            projectAssignments.Add(new ProjectTimesheetList
            {
                ProjectName = "Planned Absence",
                ProjectId = -3,
            });

            ViewBag.ProjectTimeSHeet = projectAssignments;

这是一个添加我的TimesSheet的模式，我想在下拉列表的末尾添加3 daysoff类型，所以在本例中是在“NatureBooker”之后

var projectAssignment = (from pa in db.ProjectAssignment
                                     join p in db.Projects on pa.ProjectId equals p.ID
                                     where pa.EmployeeId == EmployeeId && pa.StartDate !=null && (pa.EndDate == null || pa.EndDate >= DateTime.Now)
                                     select new ProjectTimesheetList
                                     {
                                         ProjectName = p.ProjectName,
                                         ProjectId = pa.ProjectId
                                     });

            List<ProjectTimesheetList> projectAssignments = projectAssignment.ToList();

            projectAssignments.Add(new ProjectTimesheetList
            {
                ProjectName = "Vacancy",
                ProjectId = -1,
            });

            projectAssignments.Add(new ProjectTimesheetList
            {
                ProjectName = "Unplanned Absence",
                ProjectId = -2,
            });

            projectAssignments.Add(new ProjectTimesheetList
            {
                ProjectName = "Planned Absence",
                ProjectId = -3,
            });

            ViewBag.ProjectTimeSHeet = projectAssignments;

这是我下拉列表的代码：

<select name="' + row + '_' + col + '" class="custom-select" id="tsCell_' + row + '_' + col + '" data-row="' + row + '" data-col="' + col + '">' +
                    '<option value="">----Select----</option>@Html.Raw(projsStr)</select>';

var projectAssignment = (from pa in db.ProjectAssignment
                                     join p in db.Projects on pa.ProjectId equals p.ID
                                     where pa.EmployeeId == EmployeeId && pa.StartDate !=null && (pa.EndDate == null || pa.EndDate >= DateTime.Now)
                                     select new ProjectTimesheetList
                                     {
                                         ProjectName = p.ProjectName,
                                         ProjectId = pa.ProjectId
                                     });

            List<ProjectTimesheetList> projectAssignments = projectAssignment.ToList();

            projectAssignments.Add(new ProjectTimesheetList
            {
                ProjectName = "Vacancy",
                ProjectId = -1,
            });

            projectAssignments.Add(new ProjectTimesheetList
            {
                ProjectName = "Unplanned Absence",
                ProjectId = -2,
            });

            projectAssignments.Add(new ProjectTimesheetList
            {
                ProjectName = "Planned Absence",
                ProjectId = -3,
            });

            ViewBag.ProjectTimeSHeet = projectAssignments;

'+
'----选择----@Html.Raw（projsStr）'；

解决方案：

var projectAssignment = (from pa in db.ProjectAssignment
                                     join p in db.Projects on pa.ProjectId equals p.ID
                                     where pa.EmployeeId == EmployeeId && pa.StartDate !=null && (pa.EndDate == null || pa.EndDate >= DateTime.Now)
                                     select new ProjectTimesheetList
                                     {
                                         ProjectName = p.ProjectName,
                                         ProjectId = pa.ProjectId
                                     });

            List<ProjectTimesheetList> projectAssignments = projectAssignment.ToList();

            projectAssignments.Add(new ProjectTimesheetList
            {
                ProjectName = "Vacancy",
                ProjectId = -1,
            });

            projectAssignments.Add(new ProjectTimesheetList
            {
                ProjectName = "Unplanned Absence",
                ProjectId = -2,
            });

            projectAssignments.Add(new ProjectTimesheetList
            {
                ProjectName = "Planned Absence",
                ProjectId = -3,
            });

            ViewBag.ProjectTimeSHeet = projectAssignments;

var projectAssignment=（来自db.projectAssignment中的pa
将p连接到pa上的db.Projects中。projectd等于p.ID
其中pa.EmployeeId==EmployeeId&&pa.StartDate！=null&&（pa.EndDate==null | | pa.EndDate>=DateTime.Now）
选择新建项目时间表列表
{
ProjectName=p.ProjectName，
projectd=pa.projectd
});
List projectAssignments=projectAssignment.ToList（）；
添加（新项目时间表列表）
{
ProjectName=“空缺”，
projectd=-1，
});
添加（新项目时间表列表）
{
ProjectName=“计划外缺勤”，
projectd=-2，
});
添加（新项目时间表列表）
{
ProjectName=“计划缺勤”，
projectd=-3，
});
ViewBag.ProjectTimeSHeet=项目分配；

---

结果是：

仍然不清楚您到底想要什么，但是如果我的猜测是正确的，您可能希望将“假”项目添加到您绑定到的可枚举项中（顺便说一句，不是列表）

var projectAssignment = (from pa in db.ProjectAssignment
                                     join p in db.Projects on pa.ProjectId equals p.ID
                                     where pa.EmployeeId == EmployeeId && pa.StartDate !=null && (pa.EndDate == null || pa.EndDate >= DateTime.Now)
                                     select new ProjectTimesheetList
                                     {
                                         ProjectName = p.ProjectName,
                                         ProjectId = pa.ProjectId
                                     });

            List<ProjectTimesheetList> projectAssignments = projectAssignment.ToList();

            projectAssignments.Add(new ProjectTimesheetList
            {
                ProjectName = "Vacancy",
                ProjectId = -1,
            });

            projectAssignments.Add(new ProjectTimesheetList
            {
                ProjectName = "Unplanned Absence",
                ProjectId = -2,
            });

            projectAssignments.Add(new ProjectTimesheetList
            {
                ProjectName = "Planned Absence",
                ProjectId = -3,
            });

            ViewBag.ProjectTimeSHeet = projectAssignments;

只要你明白这是绝对错误的，并且是被当场解雇的理由，你就可以：

var projectAssignment = (from pa in db.ProjectAssignment
                                     join p in db.Projects on pa.ProjectId equals p.ID
                                     where pa.EmployeeId == EmployeeId && pa.StartDate !=null && (pa.EndDate == null || pa.EndDate >= DateTime.Now)
                                     select new ProjectTimesheetList
                                     {
                                         ProjectName = p.ProjectName,
                                         ProjectId = pa.ProjectId
                                     });

            List<ProjectTimesheetList> projectAssignments = projectAssignment.ToList();

            projectAssignments.Add(new ProjectTimesheetList
            {
                ProjectName = "Vacancy",
                ProjectId = -1,
            });

            projectAssignments.Add(new ProjectTimesheetList
            {
                ProjectName = "Unplanned Absence",
                ProjectId = -2,
            });

            projectAssignments.Add(new ProjectTimesheetList
            {
                ProjectName = "Planned Absence",
                ProjectId = -3,
            });

            ViewBag.ProjectTimeSHeet = projectAssignments;

ViewBag.ProjectTimeSHeet = projectAssignment
    .Concat(new[]
        {
            new ProjectTimesheetList
            {
                ProjectName = "Vacancy",
                ProjectId = -1,
            },
            new ProjectTimesheetList
            {
                ProjectName = "Unplanned Absence",
                ProjectId = -2,
            },
            new ProjectTimesheetList
            {
                ProjectName = "Planned Absence",
                ProjectId = -3,
            },
        });

---

问题是什么？你有错误吗？@Duston没有，这个查询有效，但我不知道如何添加我想要的3个休假选项，即：“空缺”、“计划外缺勤”、“计划内缺勤”。所以我想在我的下拉列表中看到一个例子：项目1-项目2项目3，空缺，计划外缺勤，计划内缺勤问题仍然不清楚。如果您不想在前端添加更多项目，请提供更多详细信息您到底想要什么？谢谢您的回答。我修改了我的消息并添加了我想要的图像，但我会尝试使用您发送的代码，看看结果如何view bag变量拼写错误是您的，您为它选择了一个很好的位置，在一个动态变量中，没有编译时检查。是的，基本上这就是我想要的，但我不理解您的最后一句话“只要你明白这是绝对错误的，而且是被当场解雇的理由，你就可以：“哈哈？我有个错误：无法创建'XXX.Models.ProjectTimesheetList'类型的常量值。”。在此上下文中只支持基元类型或枚举类型。我需要查看导致该错误的代码，到目前为止您显示的代码（基本上没有）似乎表明我的代码应该工作。我不是开玩笑，不仅是整个模式都错了，它还显示您的数据库是在没有外键的情况下设置的，否则在这些假ID上会失败。这是因为缺乏对关系数据库设计的基本理解，而MVC将其公诸于世对MVC本身来说是一个有利因素。