如何将一个列表的一个字段值更新为另一个列表的另一个字段值？

Question

我有两个相同的类类型的列表。

List<CUSTOM_STU_DETAIL> StuList = new List<CUSTOM_STU_DETAIL>(); 
List<CUSTOM_STU_DETAIL> StuListforRollNo = new List<CUSTOM_STU_DETAIL>(); 

所以我从两个表中得到一个列表。

StuList = (from a in db.Student_Re_Admission 
          join b in db.Student_Registration on a.Registration_Id equals b.Registration_Id 

          where a.Academic_Year_Id == AcademicId && a.Company_ID == CompanyId 
          && a.COMPANY_LOCATION_ID == CompanyLocationId 
          && a.Class_Id == ClassID && a.Section_Id == SectionID 
          && a.Promoted == false && b.Delete_Flag == false 

          select new CUSTOM_STU_DETAIL 
          { 
           Registration_Id = a.Registration_Id, 
           Admission_No = a.Admission_No,        
           STUDENT_NAME = a.Student_First_Name + " "+a.Student_Middle_Name + " " + a.Student_Last_Name, 
           Class_Id = ClassID, 
           Section_Id = SectionID, 
           Academic_Year_Id = AcademicId, 
           Company_Id = CompanyId, 
           Company_Location_Id = CompanyLocationId 

           //RollNo = c.Set_Roll_No, 
          }).OrderBy(a => a.Admission_No).ToList(); 

所以现在想从与第一列表循环明智相同条件的另一个表中获取一些值..

foreach (var obj in StuList) 
       { 
        var rollNoRecord = db.Student_Roll_No_Assign.FirstOrDefault(a => a.Company_ID == obj.Company_Id && a.COMPANY_LOCATION_ID == obj.Company_Location_Id && a.Academic_Year_Id == obj.Academic_Year_Id && a.Class_Id == obj.Class_Id && a.Delete_Flag == false); 

        if (rollNoRecord != null) 
        { 
         data.RollNo = rollNoRecord.Set_Roll_No; 
        } 
        else 
        { 
         data.RollNo = string.Empty; 
        } 

        StuListforRollNo.Add(data); 


      } 

所以现在要插入数据的“SetRollNo”字段列表到第一个列表'SetRolNo'字段。

我尝试像下面，但没有得到我的意思。

1) var listfinal = StuList.Concat(StuListforRollNo); 
    2) var listfinal = StuList.Union(StuListforRollNo); 
    3) var listfinal = StuList.AddRange(StuListforRollNo); 

所有正在合并数据..

Answer 1

你为什么不改变foreach循环

foreach (var obj in StuList) 
{ 
    var rollNoRecord = db.Student_Roll_No_Assign.FirstOrDefault(a => a.Company_ID == obj.Company_Id && a.COMPANY_LOCATION_ID == obj.Company_Location_Id && a.Academic_Year_Id == obj.Academic_Year_Id && a.Class_Id == obj.Class_Id && a.Delete_Flag == false); 

    if (rollNoRecord != null) 
    { 
      //data.RollNo = rollNoRecord.Set_Roll_No; 
      obj.RollNo = rollNoRecord.Set_Roll_No; 
    } 
    else 
    { 
      //data.RollNo = string.Empty; 
      obj.RollNo = string.Empty; 
    } 
    //StuListforRollNo.Add(data); 
}