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Doing Complex Multi Joins in Linq

Posted on 2009-04-08
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Last Modified: 2013-11-11
I'm trying to get this linq query to work, but its not returning any data. Unfortunately I do need to join all those tables to get my desired data. A similar query using Sql does work with the same set of joins (of course syntax is different though).
from c in hs.Computer
join tcp in hs.TCP on c.Computer_Idn equals tcp.Computer_Idn
join cs in hs.CompSystem on c.Computer_Idn equals cs.Computer_Idn
join ns in hs.NetworkSoftware on c.Computer_Idn equals ns.Computer_Idn
join p in hs.Processor on c.Computer_Idn equals p.Computer_Idn
join mem in hs.Memory on c.Computer_Idn equals mem.Computer_Idn
join ms in hs.MemorySlot on c.Computer_Idn equals ms.Computer_Idn
where c.DeviceName.Contains(wkstn)
select new Hardware
{
     DeviceName = c.DeviceName,
     Type = c.Type,
     LoginName = c.LoginName,
     FullName = c.FullName,
     HWLastScanDate = (c.HWLastScanDate == null ? DateTime.MinValue : (DateTime)c.HWLastScanDate),
     DomainName = c.DomainName,
     ComputerLocation = c.ComputerLocation,
     LDAPLocation = c.LDAPLocation,
     SerialNum = cs.SerialNum,
     Model = cs.Model,
     Manufacturer = cs.Manufacturer,
     Cpu = p.Type,
     Speed = (p.Speed == null ? 0 : (int)p.Speed),
     TotalMemoryMB = (mem.BytesTotal == null ? 0 : (int)mem.BytesTotal) / 1024,
     MemorySlotNo = ms.SlotNo,
     SizeInstalledMemory = (ms.InstalledSize == null ? 0 : (int)ms.InstalledSize),
     ChassisType = cs.ChassisType,
     IsLaptop = cs.HasBattery,
     NicAddress = ns.NicAddress
}

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Question by:dharric08
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by:Sreedhar Vengala
ID: 24102224
shouldn't it  be for 'where' as :
....
where c.DeviceName.Contains(wkstn)
select new
{
     DeviceName = c.DeviceName,....
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Author Comment

by:dharric08
ID: 24102336
Well here's a few points. I'm using the entity framework and creating a new Hardware object. And Vs does not give any compile or runtime errors whatsoever. It just doesn't return anything.
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Expert Comment

by:Sreedhar Vengala
ID: 24102505
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Expert Comment

by:Sreedhar Vengala
ID: 24102516
sorry blank comment:   Yes all looks good for me.
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Expert Comment

by:Sreedhar Vengala
ID: 24102597
nope.. all looks good for me.  
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Expert Comment

by:Sreedhar Vengala
ID: 24102611
Ok seems problems with DateTime.MinValue - 'DateTime.MinValue underflow in SQL Server'
for test: change DateTime.MinValue to some fixed date and give a try.

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Sreedhar Vengala earned 500 total points
ID: 24102639
use SqlDateTime.MinValue instead DateTime.MinValue and give a try
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Author Comment

by:dharric08
ID: 24102672
Sree_ven, you're good! Now that you said it it seems so obvious. But what I don't get is there's no errors on compile or runtime. Shouldn't I have gotten a SqlDateTime overflow or something? Do you know why that is?
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Expert Comment

by:Sreedhar Vengala
ID: 24102726
For your info:
The reason for the overflow is because .NET framework can cover a wider range of date than SQL Server. The DateTime structure in .NET supports a range from 0:00 1/1/0001 (MinValue) to 23:59 12/31/9999 (MaxValue). Whereas, SQL Server can only support a range of 1/1/1753 to 12/31/9999. Other databases handle datetime range differently.
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Author Comment

by:dharric08
ID: 24102748
That's cool, but what I don't get is why I got no errors of any kind either during compile or at runtime. Could this be because of the Entity Framework layer hiding it?
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Expert Comment

by:Sreedhar Vengala
ID: 24102769
it raises SqlException : System.Data.SqlTypes.SqlTypeException: SqlDateTime overflow. Must be between 1/1/1753 12:00:00 AM and 12/31/9999 11:59:59 PM
Try putting your code in Try catch and catching SqlExceptions.
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