LINQ to Entities不支持指定的类型成员.仅支持初始值设定项,实体成员和实体导航属性

Question

var result =
    (from bd in context.tblBasicDetails
     from pd in context.tblPersonalDetails.Where(x => x.UserId == bd.UserId).DefaultIfEmpty()
     from opd in context.tblOtherPersonalDetails.Where(x => x.UserId == bd.UserId).DefaultIfEmpty()
     select new clsProfileDate()
     {
         DOB = pd.DOB
     });

foreach (clsProfileDate prod in result)
{
    prod.dtDOB = !string.IsNullOrEmpty(prod.DOB) ? Convert.ToDateTime(prod.DOB) : DateTime.Today;
    int now = int.Parse(DateTime.Today.ToString("yyyyMMdd"));
    int dob = int.Parse(prod.dtDOB.ToString("yyyyMMdd"));
    string dif = (now - dob).ToString();
    string age = "0";
    if (dif.Length > 4)
    age = dif.Substring(0, dif.Length - 4);
    prod.Age = Convert.ToInt32(age);
}

GetFinalResult(result);

---

protected void GetFinalResult(IQueryable<clsProfileDate> result)
{
    int from;
    bool bfrom = Int32.TryParse(ddlAgeFrom.SelectedValue, out from);
    int to;
    bool bto = Int32.TryParse(ddlAgeTo.SelectedValue, out to);

    result = result.AsQueryable().Where(p => p.Age >= from);
}

我在这里得到一个例外:

LINQ to Entities不支持指定的类型成员"Age".仅支持初始值设定项,实体成员和实体导航属性.

如果Age不在数据库中,则是我在clsProfileDate类中创建的属性,用于从DOB计算Age.对此有何解决方案？

Answer 1

您不能使用未映射到Where表达式中的数据库列的属性.您必须基于映射属性构建表达式,例如:

var date = DateTime.Now.AddYears(-from);
result = result.Where(p => date >= p.DOB);
// you don't need `AsQueryable()` here because result is an `IQueryable` anyway

作为未映射Age属性的替代,您可以将此表达式提取到静态方法中,如下所示:

public class clsProfileDate
{
    // ...
    public DateTime DOB { get; set; } // property mapped to DB table column

    public static Expression<Func<clsProfileDate, bool>> IsOlderThan(int age)
    {
        var date = DateTime.Now.AddYears(-age);
        return p => date >= p.DOB;
    }
}

然后以这种方式使用它:

result = result.Where(clsProfileDate.IsOlderThan(from));

Answer 2

很多人都会说这是一个错误的答案,因为这不是最佳实践,但你也可以在你的位置之前将其转换为List.

result = result.ToList().Where(p => date >= p.DOB);

Slauma的答案更好,但这也可行.这会花费更多,因为ToList()将对数据库执行查询并将结果移动到内存中.

Answer 3

当您不小心忘记为属性定义setter时,您也会收到此错误消息.例如:

public class Building
{
    public string Description { get; }
}

var query = 
    from building in context.Buildings
    select new
    {
        Desc = building.Description
    };
int count = query.ToList();

对ToList的调用将给出相同的错误消息.这是一个非常微妙的错误,很难检测到.