如何使用 LINQ 查询优化多个 if else 语句？

Question

我正在为我的项目创建搜索功能。如何优化包含这么多 if else 语句的查询？

我使用if else 语句来检查是否有任何空值，但这会增加代码复杂性和内存。我想减少它；如何优化我的查询，使我的查询中有最少数量的if else 语句？

    public List<tbltask> gettaskssdata(int c, int userid, string a, string StartDate, string EndDate, string ProjectID, string statusid)
    {
        List<tbltask> tbtask = new List<tbltask>();

        var selectproject = entity.tbluserprojects.Where(x => x.user_id == userid).Select(x => x.Projectid);

        if (statusid != "" && ProjectID != "" && a != "" && StartDate != "" && EndDate != "")
        {
            int pid = Convert.ToInt32(ProjectID);
            int sid = Convert.ToInt32(statusid);
            DateTime sdate = Convert.ToDateTime(StartDate).Date;
            DateTime edate = Convert.ToDateTime(EndDate).Date;
            tbtask = entity.tbltasks.Include(x => x.tblproject).Include(x => x.tbUser).Where(x => selectproject.Contains(x.ProjectId) && (x.tblproject.company_id == c) && (x.tblproject.ProjectId == pid) && (x.tblstatu.StatusId == sid) && (x.TaskName.Contains(a) || x.tbUser.User_name.Contains(a)) && (x.StartDate >= sdate && x.EndDate <= edate)).OrderByDescending(x => x.ProjectId).ToList();
        }
        else if (statusid == "" && ProjectID != "" && a != "" && StartDate != "" && EndDate != "")
        {
            int pid = Convert.ToInt32(ProjectID);
            DateTime sdate = Convert.ToDateTime(StartDate).Date;
            DateTime edate = Convert.ToDateTime(EndDate).Date;
            tbtask = entity.tbltasks.Include(x => x.tblproject).Include(x => x.tbUser).Where(x => selectproject.Contains(x.ProjectId) && (x.tblproject.company_id == c) && (x.tblproject.ProjectId == pid) && (x.TaskName.Contains(a) || x.tbUser.User_name.Contains(a)) && (x.StartDate >= sdate && x.EndDate <= edate)).OrderByDescending(x => x.ProjectId).ToList();
        }
        else if (ProjectID == "" && statusid != "" && a != "" && StartDate != "" && EndDate != "")
        {
            int sid = Convert.ToInt32(statusid);
            DateTime sdate = Convert.ToDateTime(StartDate).Date;
            DateTime edate = Convert.ToDateTime(EndDate).Date;
            tbtask = entity.tbltasks.Include(x => x.tblproject).Include(x => x.tbUser).Where(x => selectproject.Contains(x.ProjectId) && (x.tblproject.company_id == c) && (x.tblstatu.StatusId == sid) && (x.TaskName.Contains(a) || x.tbUser.User_name.Contains(a)) && (x.StartDate >= sdate && x.EndDate <= edate)).OrderByDescending(x => x.ProjectId).ToList();
        }
        else if(ProjectID!="" && StartDate == "" && EndDate == "" && statusid == ""  && a == "")
        {
            int pid = Convert.ToInt32(ProjectID);
            tbtask = entity.tbltasks.Include(x => x.tblproject).Include(x => x.tbUser).Where(x => selectproject.Contains(x.ProjectId) && (x.tblproject.company_id == c) && (x.tblproject.ProjectId == pid)).OrderByDescending(x => x.ProjectId).ToList();

        }
        else if(statusid!="" && ProjectID=="" && StartDate == "" && EndDate == ""  && a == "")
        {
            int sid = Convert.ToInt32(statusid);
            tbtask = entity.tbltasks.Include(x => x.tblproject).Include(x => x.tbUser).Where(x => selectproject.Contains(x.ProjectId) && (x.tblproject.company_id == c) && (x.tblstatu.StatusId == sid) ).OrderByDescending(x => x.ProjectId).ToList();
        }
        else if (a == "" && StartDate != "" && EndDate != "" && ProjectID != "")
        {
            int pid = Convert.ToInt32(ProjectID);
            DateTime sdate = Convert.ToDateTime(StartDate).Date;
            DateTime edate = Convert.ToDateTime(EndDate).Date;
            tbtask = entity.tbltasks.Include(x => x.tblproject).Include(x => x.tbUser).Where(x => selectproject.Contains(x.ProjectId) && (x.tblproject.ProjectId == pid) && (x.StartDate >= sdate && x.EndDate <= edate)).OrderByDescending(x => x.ProjectId).ToList();

        }
        else if (StartDate == "" && EndDate == "" && statusid != "" && ProjectID != "" && a != "")
        {
            int pid = Convert.ToInt32(ProjectID);
            int sid = Convert.ToInt32(statusid);
            tbtask = entity.tbltasks.Include(x => x.tblproject).Include(x => x.tbUser).Where(x => selectproject.Contains(x.ProjectId) && (x.tblproject.company_id == c) && (x.tblproject.ProjectId == pid) && (x.tblstatu.StatusId == sid) && (x.TaskName.Contains(a) || x.tbUser.User_name.Contains(a))).OrderByDescending(x => x.ProjectId).ToList();
        }
        else if (a == "" && StartDate == "" && EndDate == "" && ProjectID != "" && statusid != "")
        {
            int pid = Convert.ToInt32(ProjectID);
            int sid = Convert.ToInt32(statusid);
            tbtask = entity.tbltasks.Include(x => x.tblproject).Include(x => x.tbUser).Include(x => x.tblstatu).Where(x => selectproject.Contains(x.ProjectId) && x.tblproject.company_id == c && x.tblproject.ProjectId == pid && x.tblstatu.StatusId == sid).OrderByDescending(x => x.ProjectId).ToList();
        }
        else if (a != "" && StartDate == "" && EndDate == "" && ProjectID == "" && statusid == "")
        {
            tbtask = entity.tbltasks.Include(x => x.tblproject).Include(x => x.tbUser).Where(x => selectproject.Contains(x.ProjectId) && (x.tblproject.company_id == c) && (x.TaskName.Contains(a) || x.tbUser.User_name.Contains(a))).OrderByDescending(x => x.ProjectId).ToList();

        }
        else if (a != "" && ProjectID != "" && StartDate == "" && EndDate == "" && statusid == "")
        {
            int pid = Convert.ToInt32(ProjectID);
            tbtask = entity.tbltasks.Include(x => x.tblproject).Include(x => x.tbUser).Where(x => selectproject.Contains(x.ProjectId) && (x.tblproject.company_id == c) && (x.tblproject.ProjectId == pid) && (x.TaskName.Contains(a) || x.tbUser.User_name.Contains(a))).OrderByDescending(x => x.ProjectId).ToList();
        }
        else if (a != "" && StartDate != "" && EndDate != "" && ProjectID == "" && statusid == "")
        {
            DateTime sdate = Convert.ToDateTime(StartDate).Date;
            DateTime edate = Convert.ToDateTime(EndDate).Date;
            tbtask = entity.tbltasks.Include(x => x.tblproject).Include(x => x.tbUser).Where(x => selectproject.Contains(x.ProjectId) && (x.tblproject.company_id == c) && (x.TaskName.Contains(a) || x.tbUser.User_name.Contains(a)) && (x.StartDate >= sdate && x.EndDate <= edate)).OrderByDescending(x => x.ProjectId).ToList();
        }
        else
        {
            tbtask = entity.tbltasks.Include(x => x.tblproject).Include(x => x.tbUser).Where(x => selectproject.Contains(x.ProjectId) && x.tblproject.company_id == c).OrderByDescending(x => x.ProjectId).ToList();
        }
        return tbtask;
    }

Answer 1

 public List<tbltask> gettaskssdata(int? c, int? userid, string a, string StartDate, string EndDate, int? ProjectID, int? statusid)
    {
        List<tbltask> tbtask = new List<tbltask>();
        DateTime sdate = (StartDate != "") ? Convert.ToDateTime(StartDate).Date : new DateTime();
        DateTime edate = (EndDate != "") ? Convert.ToDateTime(EndDate).Date : new DateTime();
        tbtask = entity.tbltasks.Include(x => x.tblproject).Include(x => x.tbUser).
            Where(x => x.tblproject.company_id == c
                && (ProjectID == 0 || ProjectID == x.tblproject.ProjectId)
                && (statusid == 0 || statusid == x.tblstatu.StatusId)
                && (a == "" || (x.TaskName.Contains(a) || x.tbUser.User_name.Contains(a)))
                && ((StartDate == "" && EndDate == "") || ((x.StartDate >= sdate && x.EndDate <= edate)))).ToList();



        return tbtask;


    }

Answer 2

您可以有一个 LINQ 查询，而不是有很多 if 语句。

首先要做的是改变你的方法来接受可以为空的值：

public List<tbltask> gettaskssdata(int? c, int? userid, string a, DateTime? StartDate, DateTime? EndDate, int? ProjectID, int? statusid)
{

然后修改您的 LINQ 查询。如果用户为过滤器字段提供了空值，我们希望返回该行。此外，如果用户实际提供了一个值，则进行比较。例如：

tbtask = entity.tbltasks.Where(x => (!c.HasValue || x.tblproject.company_id == c.Value) && ...)