Question

我有以下POCO：

public Ticket
{
    public int Id { get; set; }
    public int IdOwner { get; set; }
    public int IdDependency { get; set; }
    public string SerialNumber { get; set; }

    public Owner Owner { get; set; } 
    public Dependency Dependency { get; set; }
}

public Owner 
{
    public int Id { get; set; }
    public string Name { get; set; }
    // Other attributes
}

public Dependency 
{
    public int Id { get; set; }
    public string Name { get; set; }
    // Other attributes
}

我想返回List只有Owner Name和Dependency Name的故障单。问题是，如果在我的过滤器中我将where传递给Owner，我会写OwnerId Dependency public List<Ticket> SelectTickets(string SerialNumber, int IdOwner, int IdDependency) { IQueryble<Ticket> query = context.Tickets.Where(t => t.SerialNumber == SerialNumber); if (IdOwner != 0) { query = query.Where( ?? ); } if (IdDependency!= 0) { query = query.Where( ?? ); } return query.ToList(); }。看看我的过滤器：

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Answer 1

如果我理解你的意思，那将是有道理的。

        public Ticket
        {
            public int Id { get; set; }
            public int OwnerId{ get; set; }
            public int DependencyId { get; set; }
            public string SerialNumber { get; set; }

            public Owner Owner { get; set; } 
            public Dependency Dependency { get; set; }
        }

        public Owner 
        {
            public int Id { get; set; }
            public string Name { get; set; }
            public List<Ticket> Tickets {get;set;}
        }

        public Dependency 
        {
            public int Id { get; set; }
            public string Name { get; set; }
            public List<Ticket> Tickets {get;set;}
        }
        public List<Ticket> SelectTickets(string serialNumber, int ownerId, int dependencyId)
        {
            return context.Tickets.Where(t => t.SerialNumber == serialNumber && t.OwnerId == ownerId && t.DependencyId == dependencyId).ToList();
        }

Answer 2

使用select语句。

query = query.Select(t => new Ticket { 
    Owner = new Owner {Name = t.Owner.Name}, 
    Dependency = new Dependency  {Name = t.Dependency.Name}
}); 
return query.ToList();

但是，在这种情况下，您似乎不想返回Ticket，而是返回其他一些对象，例如TicketSummary

public class TicketSummary {
    public OwnerName {get;set;}
    public DependencyName {get;set;}
}

然后你会

query = query.Select(t => new TicketSummary { 
    OwnerName = t.Owner.Name, 
    DependencyName = t.Dependency.Name
}); 
return query.ToList();

Answer 3

您可以将生成的查询投影到您喜欢的任何格式后过滤它。

使用此工作替换return语句还是有更复杂的要求我还没有完全理解？

return query.Select(t => new Ticket() {
    Owner = t.Owner,
    Dependency = t.Dependency;
}.ToList();

如何对查询进行分区并仅使用Linq to Entities加载一些属性？

3 个答案: