c# - 将select查询映射到一个对象会在linq中出错

Question

我有这样一个类:

public class studentpres
{
  public string stuname { set; get; }
  public  string stlastaname { set; get; }
  public string stunumber { set; get; }
  public string stumajor { set; get; }
  public string stufiled { set; get; }
  public string stuaverage { set; get; }
  public string stumobile { set; get; }
  public string stuemail { set; get; }
  public string stuprofSupervisor { set; get; }
  public string prifsuperEmail { set; get; }
}

我这样查询:

public studentpres Get_Student_List(string stuNumber)
{
    studentpres temp =
        from i in dbconnect.tblUsers
        join d in dbconnect.tblNovitiates
            on i.tblStudent.studentNumber equals d.studentNumber
        select new PresentClass.studentpres()
        {
            prifsuperEmail = d.profSupervisorUSername,
            stlastaname = i.family,
            stuaverage = i.tblStudent.average,
            stuemail = i.email,
            stufiled = i.tblStudent.field,
            stumajor = i.tblStudent.major,
            stumobile = i.mobile,
            stuname = i.name,
            stunumber = i.tblStudent.studentNumber,
            stuprofSupervisor = Return_Name_By_userName(d.profSupervisorUSername)
        };
}

但是我得到了这个错误:

Cannot implicitly convert type
'System.Linq.IQueryable<Novitiate.AdminPortal.PresentationClass.PresentClass.studentpres>' to 'Novitiate.AdminPortal.PresentationClass.PresentClass.studentpres'. An explicit conversion exists (are you missing a cast?)

我还在查询的末尾添加了一个 Tolist() 但它再次不起作用；谢谢

Answer 1

您的查询返回 IQueryable<studentpres> ，你应该只选择一条记录，使用:Single , First或其他方法:

1. 单例
2. 单一或默认
3. 首先
4. FirstOrDefault