entity-framework-4 - 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);

<小时/>

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);
}

这里我遇到了一个异常(exception):

The specified type member "Age" is not supported in LINQ to Entities. Only initializers, entity members, and entity navigation properties are supported.

年龄不在数据库中，它是我在 clsProfileDate 类中创建的属性，用于根据出生日期计算年龄。有什么解决办法吗？

Answer 1

您不能在 Where 表达式中使用未映射到数据库列的属性。您必须基于映射的属性构建表达式，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

作为未映射的 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;
    }
}

然后这样使用它:

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