无法比较“System.Collections.Generic.ICollection`1”类型的元素。仅支持原始类型、枚举类型和实体类型答案

【问题标题】：Cannot compare elements of type 'System.Collections.Generic.ICollection`1'. Only primitive types, enumeration types and entity types are supported无法比较“System.Collections.Generic.ICollection`1”类型的元素。仅支持原始类型、枚举类型和实体类型
【发布时间】：2017-12-12 21:23:05
【问题描述】：

执行以下代码时出错，LINQ 新手，无法找到如何将子对象“StudentAddresses”值分配给学生模型中的 collection 类型

IList<StudentViewmodel> students = null;

using (var CTX = new StudentEntities())
{
    students = CTX.Students.Include("JP").Select(
        s => new StudentViewmodel()
        {
            Id = s.StudentId,
            FirstName = s.FirstName,
            LastName = s.LastName,
            address =  new AddressViewmodel()
            {
                // Address1 = s.StudentAddresses.Select(t => t.Address1).ToString()
                Address1 = s.StudentAddresses.OfType<AddressViewmodel>().FirstOrDefault().Address1.ToString()
            }
        }

        ).ToList<StudentViewmodel>();
}

【问题讨论】：

标签： c# linq icollection

【解决方案1】：

我的问题已解决，这里是更新代码

        IList<StudentViewmodel> students = null;using (var CTX = new StudentEntities())
        {
            students = CTX.Students.Include("JP").Select(
                s => new StudentViewmodel()
                {
                    Id = s.StudentId,
                    FirstName = s.FirstName,
                    LastName = s.LastName,
                    address = new AddressViewmodel()
                    {
                       Address1 = s.StudentAddresses.FirstOrDefault().Address1 ,
                       Address2 = s.StudentAddresses.FirstOrDefault().Address2,
                       City = s.StudentAddresses.FirstOrDefault().City,
                       State = s.StudentAddresses.FirstOrDefault().State
                    }
                }

                ).ToList<StudentViewmodel>();
        }

【讨论】：

【解决方案2】：

我认为这可以帮助你

IList<StudentViewmodel> students = null;

using (var CTX = new StudentEntities())
{
    students = CTX.Students.Include("JP").ToList().Select(
        s => new StudentViewmodel()
        {
            Id = s.StudentId,
            FirstName = s.FirstName,
            LastName = s.LastName,
            address =  new AddressViewmodel()
            {
                // Address1 = s.StudentAddresses.ToList().Select(t => t.Address1).ToString()
                Address1 = s.StudentAddresses.OfType<AddressViewmodel>().FirstOrDefault().Address1.ToString()
            }
        }

        ).ToList<StudentViewmodel>();
}

如果评论访问属性有问题，再测试一次。确定你哪里有问题。谢谢

【讨论】：

评论地址属性并再次运行。如果有问题。再发消息。我改变答案。