Question

我在这里有一个方法应该返回一个Rpt_IncidentWithConfirm对象但是我不知道如何轻松地将它转换为一个。唯一能让我知道它如何做到下面的方式是非常低效的。

    public Rpt_IncidentWithConfirm GetIncident(string IncidentID)
    {
        db = new IncidentsDataContext();

        var incident = (from i in db.Rpt_IncidentWithConfirms
                       join d in db.DropDowns on i.incidentType equals d.value
                       where i.incidentID == Convert.ToInt32(IncidentID)
                       select new
                       {
                           i, d.text
                       }).SingleOrDefault();
        Rpt_IncidentWithConfirm r = new Rpt_IncidentWithConfirm();
        // I didn't want to have to type all this here because I have too many fields to map.

        r.bhaIncident = incident.i.bhaIncident;
        r.bitType = incident.i.bitType;
        r.Bottom_Connection = incident.i.Bottom_Connection;
        // And so on.


        return r;
    }

Answer 1

您可以直接在查询表达式中实例化Rpt_IncidentWithConfirm对象，并仅引用您需要的数据库值：

var incident = (from i in db.Rpt_IncidentWithConfirms
                join d in db.DropDowns on i.incidentType equals d.value
                where i.incidentID == Convert.ToInt32(IncidentID)
                select new Rpt_IncidentWithConfirm
                {
                   bhaIncident = i.bhaIncident
                 , bitType = i.bitType
                 , Bottom_Connection = i.Bottom_Connection
                }).SingleOrDefault();

Answer 2

不要使用anonymus type您可以使用您必须返回的类型

 select new Rpt_IncidentWithConfirm 
                   {
                       // set all properties you need
                   }).SingleOrDefault();

编辑：如果您要查询的查询是收集类型，则只需使用查询结果：

 return db.Rpt_IncidentWithConfirms.Where( ... ).FirstOrDefault();

或者如果您需要使用文本值：

//do something with incident.Text
return incident.i;

Answer 3

我实际上使用下面链接的答案来解决我的问题。这不是我想要做的，但我现在不必手动输入所有内容。 Return anonymous type results?

        public class IncidentWithDropDown
    {
        public Rpt_IncidentWithConfirm Incident { get; set; }
        public string IncidentTypeText { get; set; }
    }
    public IncidentWithDropDown GetIncident(string IncidentID)
    {
        db = new IncidentsDataContext();

        var incident = (from i in db.Rpt_IncidentWithConfirms
                       join d in db.DropDowns on i.incidentType equals d.value
                       where i.incidentID == Convert.ToInt32(IncidentID)
                       select new IncidentWithDropDown()
                       {
                           Incident = i,
                           IncidentTypeText = d.text
                       }).SingleOrDefault();

        return incident;
    }

Answer 4

您不需要在select中创建匿名类型而只需创建指定类型的对象

public Rpt_IncidentWithConfirm GetIncident(string IncidentID)
    {
        db = new IncidentsDataContext();

        var return (from i in db.Rpt_IncidentWithConfirms
                       join d in db.DropDowns on i.incidentType equals d.value
                       where i.incidentID == Convert.ToInt32(IncidentID)
                       select new Rpt_IncidentWithConfirm(){

                           bhaIncident =i.bhaIncident,
                           bitType = i.bitType,
                           Bottom_Connection = i.Bottom_Connection,
                           // And so on.
                        }).SingleOrDefault()
    }

将匿名类型转换为标称类型

4 个答案: