Question

我有来自DHCP服务器的配置数据，我把它放到这样的类中：

public class DHCP
{
    public DHCP()
    {
        this.Scopes = new List<Scope>();
    }

    public List<Scope> Scopes;

    public class Scope
    {
        public Scope(string ScopeAddress, string SubnetMask, string State, string ScopeName, string Comment)
        {
            this.ScopeAddress = ScopeAddress;
            this.SubnetMask = SubnetMask;
            this.State = State;
            this.ScopeName = ScopeName;
            this.Comment = Comment;
        }

        public Scope(string ScopeAddress, string SubnetMask, string State, string ScopeName, string Comment, bool initClients)
        {
            this.ScopeAddress = ScopeAddress;
            this.SubnetMask = SubnetMask;
            this.State = State;
            this.ScopeName = ScopeName;
            this.Comment = Comment;

            if (initClients)
                this.Clients = new List<Client>();
        }

        public void InitClients()
        {
            this.Clients = new List<Client>();
        }

        public void InitReservations()
        {
            this.Reservations = new List<Reservation>();
        }

        public string ScopeAddress { get; set; }
        public string SubnetMask { get; set; }
        public string State { get; set; }
        public string ScopeName { get; set; }
        public string Comment { get; set; }

        public List<Client> Clients;
        public List<Reservation> Reservations;
    }

    public class Client
    {
        public Client(string IPAddress, string SubnetMask, string UniqueID, string LeaseExpires, string ClientType)
        {
            this.IPAddress = IPAddress;
            this.SubnetMask = SubnetMask;
            this.UniqueID = UniqueID;
            this.LeaseExpires = LeaseExpires;
            this.ClientType = ClientType;
        }

        public string IPAddress { get; set; }
        public string SubnetMask { get; set; }
        public string UniqueID { get; set; }
        public string LeaseExpires { get; set; }
        public string ClientType { get; set; }
        public Reservation ClientReservation { get; set; }
    }

    public class Reservation
    {
        public Reservation(string IPAddress, string UniqueID, bool ReservationActive)
        {
            this.IPAddress = IPAddress;
            this.UniqueID = UniqueID;
            this.ReservationActive = ReservationActive;
        }

        public string IPAddress { get; set; }
        public string UniqueID { get; set; }
        public string Name { get; set; }
        public string Description { get; set; }
        public string Type { get; set; }
        public bool ReservationActive { get; set; }
    }
}

然后我在gridview上使用了List<DHCP.Client> DataSource。当我将其中一个数据字段设置为ClientReservation.ReservationActive时，我收到一个未找到的错误。

我用List＆lt;＆gt;尝试了这个这根本就没有NULL数据。所以我有问题：

这可以完成吗？如果我有一个Client.ClientReservation == null的对象，我怎么能在DataBind()上处理它而没有错误？

Answer 1

问题在于，您可以看到除了ReservationActive之外，您在构造函数中为所有属性分配了一个值。事实上它仍然是null，这就是你得到错误的原因。所以你应该这样做：

public class Client
{
    public Client(string IPAddress, string SubnetMask, string UniqueID, string LeaseExpires, string ClientType, Reservation ClientReservation)
    {
        this.IPAddress = IPAddress;
        this.SubnetMask = SubnetMask;
        this.UniqueID = UniqueID;
        this.LeaseExpires = LeaseExpires;
        this.ClientType = ClientType;
        this.ClientReservation = ClientReservation;
    }

    public string IPAddress { get; set; }
    public string SubnetMask { get; set; }
    public string UniqueID { get; set; }
    public string LeaseExpires { get; set; }
    public string ClientType { get; set; }
    public Reservation ClientReservation { get; set; }
}

传递非空值。否则，您可以通过这种方式初始化它，而无需通过构造函数传递它：

Client client = new Client();
client.ClientReservation = new Reservation("127.0.0.1", "ID", true); //example

然后您可以使用myClient.ClientReservation而不会收到任何错误。

修改

另一个建议。因为您需要添加一些Client。你可以用这种方式实现这种可能性：

public Scope { //... public void AddClient(string IPAddress, string SubnetMask, string UniqueID, string LeaseExpires, string ClientType, Reservation ClientReservation){ Clients.Add(new Client(IPAddress, SubnetMask, UniqueID, LeaseExpires, ClientType, ClientReservation)); } }

然后：

Scopes = new List<Scope>(); Scope scope = new Scope(/*...*/); scope.AddClient(new Client(/*...*/)); Scopes.Add(scope);

Answer 2

我找到了解决这两个问题的方法。通过使用这样的模板字段：

<asp:TemplateField>
  <ItemTemplate>
    <%#DataBinder.Eval(Container.DataItem, "ClientReservation.ReservationActive")%>
  </ItemTemplate>
 </asp:TemplateField>

它得到嵌套类（子属性）的值，如果ClientReservation为NULL，则忽略它而不会出错。

Gridview中的嵌套类

2 个答案: