Question

如何使用Linq进行搜索时使用日期。我想我在宣言上遗漏了一些东西

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

可能是拼写错误，但您需要将 searchDateFrom / searchDateTo 转换为DateTime，并且您的linq语句中还有两个额外的括号

Answer 2

这是我设置单元测试以查看正在发生的事情。

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; }
    }

同时检查＆amp;到。

Answer 3

我还建议使用更干净的缩进，更容易理解和计算括号和内容。

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

HttpRequest.Form是NameValueCollection，您可以通过int / string索引器在其中获取字符串。也就是说，Request.Form["ReceivedDateFrom"]返回一个字符串，您无法将其分配给类型为DateTime且没有任何转换的变量。您可以尝试使用DateTime.ParseExact方法将字符串转换为DateTime。但是，如果您不能保证字符串格式正确，则可以使用TryParse方法。

Linq搜索日期

4 个答案: