C#将基类型列表转换为派生类型列表[重复]

Question

我将基类型列表转换为派生类型列表

List<TicketDetail> ticketDetails = listResult.Cast<TicketDetail>().ToList();
List<TicketDetail> ticketDetails = listResult.ConvertAll(x => (TicketDetail) x).ToList();

我都试过了，每一个都扔了：

System.InvalidCastException：无法转换类型的对象 “WorkOrder.Service.Ticket”键入“WorkOrder.Service.TicketDetail”。 这是我的课

namespace WorkOrder.Service
{
    using System;
    [DataContract]
    [KnownType(typeof(TicketDetail))]
    public partial class Ticket
    {
        public int RecordId { get; set; }
        public long TicketId { get; set; }
        public string Summary { get; set; }
        public string Details { get; set; }
        public int CategoryId { get; set; }
        public System.DateTime CreatedOn { get; set; }
        public string CreatedBy { get; set; }
        public string Status { get; set; }
        public string TicketSource { get; set; }
        public string TicketType { get; set; }
        public string ManagedByGroup { get; set; }
        public string ManagedByUser { get; set; }
        public Nullable<long> SubscriptionId { get; set; }
        public string PriorityLevel { get; set; }
        public string Impact { get; set; }
        public string ImpactOnBusiness { get; set; }
        public string Risk { get; set; }
        public string Comment { get; set; }
        public Nullable<System.DateTime> PlannedStartDatetime { get; set; }
        public Nullable<System.DateTime> ActualStartDatetime { get; set; }
        public Nullable<System.DateTime> PlannedDeadlineDatetime { get; set; }
        public Nullable<System.DateTime> ActualDeadlineDatetime { get; set; }
        public System.DateTime TransactionDatetime { get; set; }
        public string AssignedToGroup { get; set; }
        public string AssignedToUser { get; set; }
        public string CategoryName { get; set; }
        public int CreatedById { get; set; }
        public int StatusId { get; set; }
        public int SourceId { get; set; }
        public int TypeId { get; set; }
        public int ManagedByGroupId { get; set; }
        public Nullable<int> ManagedByUserId { get; set; }
        public int AssignedToGroupId { get; set; }
        public Nullable<int> AssignedToUserId { get; set; }
        public int PriorityLevelId { get; set; }
        public int ImpactLevelId { get; set; }
        public int ImpactOnBusinessLevelId { get; set; }
        public int RiskLevelId { get; set; }
    }
}

派生类：

namespace WorkOrder.Service
{
    [DataContract]
    public class TicketDetail : WorkOrder.Service.Ticket
    {
        [DataMember]
        public List<WorkLogView> WorkLogs { get; set; }
    }
}

Answer 1

您不能从Ticket 转换为TicketDetail，因为TicketDetail 是Ticket 的派生类型，但反过来是不可能的。

您需要使用 Linq Select 表达式创建新对象，例如： listResult.Select(item => new TicketDetail() { /* ... */ }).ToList()

编辑

为避免在Select 表达式中设置所有属性，请在TicketDetail 中创建一个构造函数，该构造函数接受Ticket：

namespace WorkOrder.Service
{
    [DataContract]
    public class TicketDetail : WorkOrder.Service.Ticket
    {
        public TicketDetail(Ticket ticket)
        {
             this.StatusId = ticket.StatusId;
        }

        [DataMember]
        public List<WorkLogView> WorkLogs { get; set; }
    }
}

然后就这样做：

List<TicketDetail> ticketDetails = listResult.Select(item => new TicketDetail(item)).ToList()