LINQ查询出生日期以获得年龄
我正在对员工的出生日期进行查询（在northwind db中），我希望得到他们的年龄。 我怎么做？
private void Form1_Load(object sender, EventArgs e) { using (NorthWindDataContext dataContext = new NorthWindDataContext()) { DateTime today = DateTime.Today; var q1 = from z in dataContext.Employees select new { z.FirstName, today-z.BirthDate <---- problem here }; dataGridView1.DataSource = q1; } } 在我的最终网格中，我想要年龄列。
birthdate = 29/05/1969（示例）
这可能很棘手，因为你需要确保今年过生日，否则你的年龄将会超过一岁。
var query = from e in dataContext.Employees //get the difference in years since the birthdate let years = DateTime.Now.Year - e.BirthDate.Year //get the date of the birthday this year let birthdayThisYear = e.BirthDate.AddYears(years) select new { //if the birthday hasn't passed yet this year we need years - 1 Age = birthdayThisYear > DateTime.Now ? years - 1 : years };
这样做具有在生成的SQL查询中计算年龄的优点。 这意味着您无需遍历客户端的结果集来计算年龄。
如果您感兴趣，它将生成以下SQL：
-- Region Parameters DECLARE @p0 Int = 2013 DECLARE @p1 DateTime = '2013-02-14 09:08:46.413' DECLARE @p2 Int = 1 -- EndRegion SELECT [t2].[value] AS [years], [t2].[value2] AS [birthdayThisYear], (CASE WHEN [t2].[value2] > @p1 THEN [t2].[value] - @p2 ELSE [t2].[value] END) AS [Age] FROM ( SELECT [t1].[value], DATEADD(YEAR, [t1].[value], [t1].[BirthDate]) AS [value2] FROM ( SELECT [t0].[BirthDate], @p0 - DATEPART(Year, [t0].[BirthDate]) AS [value] FROM [Employees] AS [t0] ) AS [t1] ) AS [t2]
创建具有3个属性的匿名对象： FirstName ， Age和BirthDate （这是检查员工生日是否已过去今年所需的时间）。
var q1 = (from z in dataContext.Employees select new { FirstName = z.FirstName, Age = today.Year - z.BirthDate.Year, BirthDate = z.BirthDate }).ToList(); q1.ForEach(x => if (x.BirthDate > today.AddYears(-x.Age)) { x.Age--; });
根据评论（这是正确的）你还应该检查BirthDate是否已经通过，所以在选择数据后你必须运行检查。
你需要一个命名属性，如下所示：
private void Form1_Load(object sender, EventArgs e) { using (NorthWindDataContext dataContext = new NorthWindDataContext()) { DateTime today = DateTime.Today; var q1 = from z in dataContext.Employees select new { Name = z.FirstName, Age = today - z.BirthDate }; dataGridView1.DataSource = q1; } }
var temp = from o in dataContext.Employees select new { FirstName = o.FirstName, Age = DateTime.Now.Year - z.BirthDate.Year -1 };
var q1 = from z in dataContext.Employees select new { z.FirstName, z.BirthDate, Age = DateTime.Now.Year - z.BirthDate.Year };