从 SQL 创建 LINQ

Question

我正在尝试根据 Sql 创建 Linq 查询，但无法使其正常工作。

SQL

"select distinct(roomName) as RoomName, tblroomid as RoomId
 from TblMaster,tblrooms 
 where tblrooms.tblroomid = TblPresentationMaster.tblroomid 
 and convert(datetime, PDay, 101)='" + Pday + "'";

LINQ

(from tblRoom in tblRooms.AsEnumerable()
 join tblPMaster in tblMaster.AsEnumerable()
 on tblRoom.Field<int>("tblroomid") equals tblPMaster.Field<int>("tblroomid")
 where tblPMaster.Field<string>("pday") == Pday 
 select tblRoom.Field<string>("roomName")).Distinct();

如果我尝试运行它

foreach (var myReader in query)
{
}

我收到以下错误

Specified cast is not valid.

这些是以下变量中的值，希望这有助于捕获错误

tblPMaster.pday = Jun 28 2011 12:00AM
Parameter Pday = 28/11/2011

我不知道我哪里做错了。有人可以帮助获得正确的 LINQ 查询吗？

Answer 1

将此转换为日期而不是字符串

tblPMaster.Field<string>("pday")

Answer 2

@javadotnetcoder，谢谢你的澄清。我想我找到了解决方案...

试一试：

DataTable tblMaster = new DataTable();
DataColumn dc = new DataColumn("pday", Type.GetType("System.String"));
tblMaster.Columns.Add(dc);
tblMaster.Rows.Add(new Object[]{"Nov 28 2011 12:00AM"});
tblMaster.Rows.Add(new Object[]{"Apr 27 2013 11:10PM"});
tblMaster.Rows.Add(new Object[]{"Jul 18 2011 12:00AM"});
tblMaster.Rows.Add(new Object[]{"Mar 19 2012 10:01PM"});

DateTime PDay = new DateTime(2011,11,28);

//foreach(var row in tblMaster.AsEnumerable())
//{
//  Console.WriteLine("{0}", Convert.ToDateTime(row[0]));
//}

var qry = tblMaster.AsEnumerable()
         .Where(p=>Convert.ToDateTime(p.Field<string>("pday"))==PDay);
//qry.Dump();

以上代码已在 LinqPad 上测试。也适用 ;)

干杯，Maciej

从 SQL 创建 LINQ

Creating LINQ from SQL

c#

linq

tsql

ado.net

linq-to-dataset