Question

我有一个包含两个表（UserData）和（UserDetails）的数据库。我使用LINQtoEntities。这里的问题是不接受LINQ查询：

Details = c.ToList<UserDetails>()

错误是：

实例参数：无法转换为＆＃39; System.Collections.Generic.IEnumerable＆lt; mynamespace.UserDetails＆gt;＆＃39; to＆＃39; System.Collections.Generic.IEnumerable＆lt; System.Collections.IEnumerable＆gt;＆＃39;

public class UserData
{

    public int Index{ get; set; }
    public string Name{ get; set; }
    public string PersonalNo { get; set; }
    public <List<UserDetails>> Details { get; set; }
}

public struct UserDetails
{
    public int Age;
    public string profession;
    public string gender;
}

public IEnumerable<Userdata> GetUserData()
{
    var context = new DatabaseEntities();

    var Results =
        from a in context.UserData
        join b in context.UserDetails on a.Index equals b.Index into c
        select new UserData{ Index = a.Index, Name = a.Name, PersonalNo = a.PersonalNo, 
                             Details= c.ToList<UserDetails>() };

    return Results;          
}

有没有人可以帮助我。如果需要更多信息，请询问。感谢。

Answer 1

以下示例正常运行。为了使它工作，你可以使用对象。见下面的例子：

public class UserData
{
   public int Index{ get; set; }
   public string Name{ get; set; }
   public string PersonalNo { get; set; }
   public List<object> Details { get; set; }
}

public class UserDetails
{
   public int Age;
   public string profession;
   public string gender;
}

public IEnumerable<Userdata> GetUserData()
{
   var context = new DatabaseEntities();

   var Results =
       from a in context.UserData
       join b in context.UserDetails on a.Index equals b.Index into c
       select new UserData{ Index = a.Index, Name = a.Name, PersonalNo = a.PersonalNo, 
                            Details= c.ToList<object>() };

   return Results;          
}

Watch窗口中的Type为“object {MyTestApp.UserDetails}” 所以基本上它正如我所做的那样工作。但我需要适当地施展它。可能现在更容易帮助我。有什么建议吗？

LINQ to Entities特殊数据库查询无法正常工作

1 个答案: