c# - LINQ to Entities 无法识别方法 'System.DateTime GetValueOrDefault()'

Question

努力使用非常简单的代码，这些代码在其他类中可以使用类似代码的地方不起作用。如果我删除 GetValueOrDefault()，它将无法编译。我也在使用 System.Linq。我收到此运行时错误:LINQ to Entities 无法识别方法“System.DateTime GetValueOrDefault()”。有任何想法吗？

    public List<AddressModel> GetAll(string customer_number)
    {           
        addresses = (from a in db.ADDRESS
                      where a.CUSTOMER_NUMBER.Equals(customer_number)
                      select new AddressModel
                       {
                           Address_Id = a.ADDRESS_ID,
                           System_Id = a.SYSTEM_ID,
                           Customer_Number = a.CUSTOMER_NUMBER,
                           Address_Type = a.ADDRESS_TYPE,
                           Changed_On = a.CHANGED_ON.GetValueOrDefault(DateTime.MinValue),
                           Created_On = a.CREATED_ON.GetValueOrDefault(DateTime.MinValue),
                           Email = a.EMAIL
                       }).ToList(); 

        return addresses;
    }

---

Why would Entity Framework not be able to use ToString() in a LINQ statement?讨论了 Linq-to-Entites 无法翻译 .ToString() 方法的类似问题，但那里建议的方法 - 根本不使用方法或让 Microsoft 修复它对这种情况不起作用。

Answer 1

您应该能够使用 Null Coalescing运算符 ??:

addresses = (from a in db.ADDRESS
             where a.CUSTOMER_NUMBER.Equals(customer_number)
             select new AddressModel
             {
                 Address_Id = a.ADDRESS_ID,
                 System_Id = a.SYSTEM_ID,
                 Customer_Number = a.CUSTOMER_NUMBER,
                 Address_Type = a.ADDRESS_TYPE,
                 Changed_On = a.CHANGED_ON ?? DateTime.MinValue,
                 Created_On = a.CREATED_ON ?? DateTime.MinValue,
                 Email = a.EMAIL
              }).ToList();