Linq 搜索日期

Question

如何使用 Linq 进行搜索时使用日期。我想我在声明中遗漏了一些内容

string searchName = Request.Form["PersonName"];
DateTime searchDateFrom = Request.Form["ReceivedDateFrom"];
DateTime searchDateTo = Request.Form["ReceivedDateTo"];

var Results = (from va in _db.myTable
       where ((va.PersonName.Contains(searchName)
               && (va.ApplicationReceivedDate > searchDateFrom 
                   && va.ApplicationReceivedDate < searchDateTo)
               select va).ToList();

Answer 1

HttpRequest.Form 是一个 NameValueCollection，可以通过 int/string 获取其中的字符串索引器。也就是说，Request.Form["ReceivedDateFrom"] 返回一个字符串，您不能在不进行任何转换的情况下将其分配给类型为 DateTime 的变量。您可以尝试 DateTime.ParseExact< /a> 方法将字符串转换为 DateTime。但如果您不能保证字符串的格式正确，您可以使用 TryParse 方法。

Answer 2

可能是一个拼写错误，但您需要将 searchDateFrom / searchDateTo 转换为 DateTime，并且 linq 语句中有两个额外的开括号

Answer 3

我还建议使用更清晰的缩进，这样更容易跟踪和计算括号和其他内容。

string searchName = Request.Form["PersonName"];
DateTime searchDateFrom = Request.Form["ReceivedDateFrom"];
DateTime searchDateTo = Request.Form["ReceivedDateTo"];

var Results = (from va in _db.myTable
              where va.PersonName.Contains(searchName)
              && (va.ApplicationReceivedDate > searchDateFrom 
              && va.ApplicationReceivedDate < searchDateTo)
              select va).ToList();

Answer 4

这是我设置单元测试来查看发生了什么的时候。

检查括号并从字符串转换为日期时间：

[TestMethod]
    public void TestMethod1()
    {
        List<myTable> myTables = new List<myTable>();
        for (int month = 1; month < 10; month++)
        {
            for (int day = 1; day < 20; day++)
            {
                myTables.Add(new myTable { PersonName = "Person " + month.ToString() + " " + day.ToString(), ApplicationReceivedDate = new DateTime(2011, month, day) });
            }
        }

        string searchName = "Person";
        DateTime searchDateFrom = Convert.ToDateTime("2011-01-02");
        DateTime searchDateTo = Convert.ToDateTime("2011-01-03");

        var Results = (from va in myTables
                       where va.PersonName.Contains(searchName)
                               && va.ApplicationReceivedDate >= searchDateFrom
                                   && va.ApplicationReceivedDate < searchDateTo
                       select va);

        Assert.AreEqual(Results.Count(), 1);
    }

    public class myTable
    {
        public string PersonName { get; set; }
        public DateTime ApplicationReceivedDate { get; set; }
    }

还要检查 & 中的搜索到。