Question

我有一个LINQ查询，因为存储结果的变量将用于＆＃34; if＆＃34;声明，我必须在查询之前初始化它。这需要创建一个类，因为列表中存储了不同的数据类型 - 但是我在LINQ查询中制作类成员时遇到了麻烦，我不确定原因。

类别：

public class OtherProgramType
{
    public string State { get; set; }
    public string PrgName { get; set; }
    public short? ProgramTypeID { get; set; }
    public string DisplayText { get; set; }

}

代码：

List<OtherProgramType> otherPrograms;
otherPrograms = (from hm in db.HabitatManagement
                             join svy in db.Survey on hm.SurveyID equals svy.SurveyID
                             join iu in db.InventoryUsers on hm.UserID equals iu.UserID
                             join pt in db.ProgramType on hm.ProgramTypeID equals pt.ProgramTypeID
                             where pt.Program != "State Agency Public Land Programs"
                             && pt.Program != "State Agency Private Land Programs"
                             && svy.ReportingYear == (from svy in db.Survey
                                                      where svy.ReportingYear.HasValue
                                                      select svy.ReportingYear.Value).Max()
                             || pt.Program != "State Agency Public Land Programs"
                             && pt.Program != "State Agency Private Land Programs"
                             && svy.ReportingYear == (from svy in db.Survey
                                                      where svy.ReportingYear.HasValue
                                                      select svy.ReportingYear.Value).Max() - 1
                             select new
                             {
                                 iu.StateID,
                                 hm.ProgramTypeID,
                                 pt.Program
                             })
                             .Distinct()
                             .Select(x => new OtherProgramType { x.StateID, x.Program, x.ProgramTypeID, DisplayText = x.StateID.ToString() + ", " + x.Program.ToString() })
                             .OrderBy(x => x.StateID)
                             .ToList();

这是我想要新类成员的行： .Select(x => new OtherProgramType { x.StateID, x.Program, x.ProgramTypeID, DisplayText = x.StateID.ToString() + ", " + x.Program.ToString() })

x.StateID, x.Program, x.ProgramTypeID在红色曲线中加下划线，并且表示＆＃34;无效的初始化成员声明符。＆＃34;

Answer 1

您需要说明字段分配，特别是因为x中的字段与您的类型OtherProgramType

中的字段不匹配

.Select(x => new OtherProgramType 
{
    State = x.StateID, 
    PrgName = x.Program, 
    ProgramTypeID = x.ProgramTypeID, 
    DisplayText = x.StateID.ToString() + ", " + x.Program.ToString() 
})

Answer 2

您需要提供要分配给的属性的名称：

.Select(x => new OtherProgramType {
     State = x.StateID,
     PrgName = x.Program,
     ProgramTypeID = x.ProgramTypeID, 
     DisplayText = x.StateID.ToString() + ", " + x.Program.ToString() 
})

Answer 3

以上答案都绝对正确。只是添加：

如果你的类有一个构造函数来获取你的代码可能的所有参数：

public class OtherProgramType
{
  public OtherProgramType(string s, string pn, short? ptid, string dt)
  {
    this.State = s;
    this.PrgName = pn;
    this.ProgramTypeID = ptid;
    this.DisplayText = dt;
  }

  public string State { get; set; }
  public string PrgName { get; set; }
  public short? ProgramTypeID { get; set; }
  public string DisplayText { get; set; }
}

现在适当的行可能是：

...
.Select(x => new OtherProgramType ( x.StateID, x.Program, x.ProgramTypeID, x.StateID.ToString() + ", " + x.Program.ToString() ))
...

请注意()而不是{}。

通过LINQ查询添加新的类成员

3 个答案: