I've a table with over 100 column (including blobs) and I want to make a copy of object only with a few filled columns.
right now I'm doing it by selecting needed columns and doing a round-trip serialize and deserialize with Json.NET which is not efficient. what's the best way to handle this scenario?
BL.Case mCase;
BL.Case temp = db.Cases.Select(
xx => new
{
CaseID = xx.CaseID,
FirstName = xx.FirstName,
LastName = xx.LastName
}).FirstOrDefault(u => u.CaseID == CaseID);
mCase = Newtonsoft.Json.JsonConvert.DeserializeObject<BL.Case>(Newtonsoft.Json.JsonConvert.SerializeObject(temp));
Use AutoMapper.
Do something like this:
BL.Case mCase = null;
var temp = db.Cases.Select(
xx => new
{
CaseID = xx.CaseID,
FirstName = xx.FirstName,
LastName = xx.LastName
}).FirstOrDefault(u => u.CaseID == CaseID);
if (temp != null)
{
mCase = Mapper.DynamicMap<BL.Case>(temp);
}
Another solution that requires a bit more code (but might perform better) is to do the following:
In case you need a single item:
BL.Case mCase = null;
var temp = db.Cases.Select(
xx => new
{
CaseID = xx.CaseID,
FirstName = xx.FirstName,
LastName = xx.LastName
}).FirstOrDefault(u => u.CaseID == CaseID);
if (temp != null)
{
mCase = new Case()
{
CaseID = temp.CaseID,
FirstName = temp.FirstName,
LastName = temp.LastName,
};
}
If you need multiple items:
var temp = db.Cases.Select(
xx => new
{
CaseID = xx.CaseID,
FirstName = xx.FirstName,
LastName = xx.LastName
}); //Here you can filter your query if you want using Where
var result = temp
.ToList() //This will actually execute the query on the database
.Select(x => new Case() //Now you can do this since now we are working on in-memory data
{
CaseID = x.CaseID,
FirstName = x.FirstName,
LastName = x.LastName
});
Related
I have two lists of same type with different key value pairs,
List1 has "isPermanent = true" and List2 has false value and also
List1 has an extra key "nextVacationDate".
Im trying to do union of these as below but im afraid I will still get the duplicates because of different values. I need to merge both lists in to one list and order by List1 first (Permanent employees first)..is there a better way to do this using LINQ?
public newList1 List1(string abcd)
{
var result = serviceMethod1(abcd);
var newList1 = new List<emp>();
if (result == null) return null;
newList.AddRange(
result.Select(x => new Model
{
firstName = x.FName,
secondName = x.SName,
address = x.Address,
employeeId = x.EmpId,
isPermanent = true,
nextVacationDate =x.VacDt,
salary = x.Bsalary
}));
return newList1;
}
public newList2 List2(string defg)
{
var result = serviceMethod2(defg);
var newList2 = new List<emp>();
if (result == null) return null;
newList.AddRange(
result.Select(x => new Model
{
firstName = x.FName,
secondName = x.SName,
address = x.Address,
employeeId = x.EmpId,
isPermanent = false,
salary = x.Bsalary
}));
return newList2;
}
private List<emp> EmployyeList(List<emp> newList1, List<emp> newList2)
{
var sortedEmpList1 = newList1.OrderBy(i => i.Fname);
var sortedEmpList2 = newList2.OrderBy(i => i.Fname);
List<MeterModel> combinedList = newList1.Union(newList2) as List<emp>;
return combinedList;
}
You can filter the 2nd list to avoid duplicates:
newList1.Union(newList2.Where(emp2 => !newList1.Any(emp1 => emp1.employeeId == emp2.employeeId)))
Per iteration, this query creates an EmailRecipient for each populated address. Can it be done without the multiple iteration?
var addedRecipients = (from oldRecip in oldEmailRecipients
where !string.IsNullOrWhiteSpace(oldRecip.EmailAddress1)
select new EmailRecipient
{
UserName = oldRecip.UserName,
EmailAddress = oldRecip.EmailAddress1
}
).Union(from oldRecip in oldEmailRecipients
where !string.IsNullOrWhiteSpace(oldRecip.EmailAddress2)
select new EmailRecipient
{
UserName = oldRecip.UserName,
EmailAddress = oldRecip.EmailAddress2
});
You can use SelectMany extension method:
var addedRecipients = oldEmailRecipients.SelectMany(e=>
{
var result= new List<EmailRecipient>();
if(!string.IsNullOrWhiteSpace(e.EmailAddress1))
{
result.Add(new EmailRecipient
{
UserName = e.UserName,
EmailAddress = e.EmailAddress1
});
}
if(!string.IsNullOrWhiteSpace(e.EmailAddress2))
{
result.Add(new EmailRecipient
{
UserName = e.UserName,
EmailAddress = e.EmailAddress2
});
}
return result;
});
Update
The solution that I show above only works in Linq to Objects. Your comment suggest me you are using EF. A simple solution could be call AsEnumerable method before SelectMany to make the switch to Linq to Objects, but that could end harming your performance if you are not filtering your recipients first.
Another solution could be selecting only data that you need first from you server before of call SelectMany to not load other columns you don't need in this case:
...Where(...)
.Select(r=>new{UserName=r.UserName,
EmailAddress1=r.EmailAddress1,
EmailAddress2=r.EmailAddress2 })
.AsEnumerable()
.SelectMany(...);
Sticking with query syntax, and making sure to only process oldEmailRecipients items who have either a non-null/whitespace EmailAddress1 or a non-null/whitespace EmailAddress2:
var addedRecipients =
from oldEmail in oldEmailRecipients
let hasEmail1 = !string.IsNullOrWhiteSpace(oldEmail.EmailAddress1)
let hasEmail2 = !string.IsNullOrWhiteSpace(oldEmail.EmailAddress2)
where hasEmail1 || hasEmail2
let emailUserNameCombos = hasEmail1 && hasEmail2
? new[]
{
new {Email = oldEmail.EmailAddress1, oldEmail.UserName},
new {Email = oldEmail.EmailAddress2, oldEmail.UserName}
}
: hasEmail1
? new[] {new {Email = oldEmail.EmailAddress1, oldEmail.UserName}}
: new[] {new {Email = oldEmail.EmailAddress2, oldEmail.UserName}}
from emailUsername in emailUserNameCombos
select new EmailRecipient
{
UserName = emailUsername.UserName,
EmailAddress = emailUsername.Email
};
You can build an inline array to add both emails and flatten them out using SelectMany.
var addedRecipients = from oldRecip in oldEmailRecipients
let emails =
new[] {oldRecip.EmailAddress1, oldRecip.EmailAddress2}.Where(e => !string.IsNullOrWhiteSpace(e))
from email in emails
where emails.Any()
select new EmailRecipient
{
UserName = oldRecip.UserName,
EmailAddress = email
};
When your EmailRecipient has more than two email address then you could do this:
// Just building a pseudo dataclass
List<Recipient> oldEmailRecipients = Enumerable.Range(1, 10).Select(item => new Recipient()
{
Name = "Recipient" + item,
EmailAddress1 = "pseudo" + item + "#gmail.com",
EmailAddress2 = "pseudo" + (item + 1) + "#gmail.com",
//EmailAddress3 = "pseudo" + (item + 2) + "#gmail.com",
EmailAddress3 = "",
EmailAddress4 = "pseudo" + (item + 3) + "#gmail.com",
} ).ToList( )
// create anonymous object for each recipient and a list of valid adresses
var query = from mailRecipients in oldEmailRecipients
select new
{
Name = mailRecipients.Name,
Addresses = new List<string>()
{
mailRecipients.EmailAddress1,
mailRecipients.EmailAddress2,
mailRecipients.EmailAddress3,
mailRecipients.EmailAddress4
}.Where(item => string.IsNullOrEmpty( item ) == false )
};
// create an EmailRecipient for each valid combination
var final = from item in query
from address in item.Addresses
select new EmailRecipient
{
Name = item.Name,
Address = address
};
I was trying to get employee list which not already available in another list. but im getting only first element from array list.
ex : if i try EmployeeId = new int[2] {5, 2}; the list excluding only '5'. So please help me correct my below code.
public JsonResult GetEmployees(int[] EmployeeId)
{
var dbs = new dbContext();
if (EmployeeId != null)
{
foreach (var emp in EmployeeId)
{
var EmpList = dbs.Employees.Select(e => new
{
EmployeeId = e.EmployeeId,
Name = e.EmployeeName,
Job = e.Job.JobName,
Currency = e.Currency.CurrencyName,
Amount = e.Amount
}).Where(o => o.EmployeeId != emp);
return Json(EmpList, JsonRequestBehavior.AllowGet);
}
}
return null
}
Try this :
var employeeList = dbs.Employees.
.Where(e => EmployeeId.All(x=> x != e.EmployeeId))
.Select(e => new
{
EmployeeId = e.EmployeeId,
Name = e.EmployeeName,
Job = e.Job.JobName,
Currency = e.Currency.CurrencyName,
Amount = e.Amount
});
return Json(EmpList, JsonRequestBehavior.AllowGet);
}
Have you tried stepping through your code?
Your foreach iterates over your EmployeeId array.
Since you have a return statement in your foreach it exits the function at that point and it only uses the first element of your array.
You need something like this:
public JsonResult GetEmployees(int[] EmployeeId)
{
var dbs = new dbContext();
if (EmployeeId != null)
{
var EmpList = dbs.Employees.Where(EmployeeId.Contains(e.EmployeeId))
.Select(e => new
{
EmployeeId = e.EmployeeId,
Name = e.EmployeeName,
Job = e.Job.JobName,
Currency = e.Currency.CurrencyName,
Amount = e.Amount
}).Where(o => o.EmployeeId != emp);
return Json(EmpList, JsonRequestBehavior.AllowGet);
}
return null;
}
I have a LINQ query, I need to return all the customers in our database, however not all of them have a middle name. This is my query:
select new
{
firstName = a.firstname,
middleName = a.middlename,
lastName = a.lastname,
};
foreach(var c in queryAccount)
{
console.writeline(c.firstname);
console.writeline(c.middlename);
console.writeline(c.lastname);
}
What I am looking for is something similar to:
if (c.middlename != null)
{
console.writeline(c.middlename);
}
Does anyone know how I could get this to work?
You can simply use Null Colaescing operator:-
select new {
firstName = a.firstname,
middleName = a.middlename ?? String.Empty,
lastName = a.lastname,
};
Rahul's answer is correct. Additionally in case you don't want to assign 'middleName' at all you can do:
Select(x =>
{
var obj = new TestData
{
Lastname = x.Lastname,
Firstname = x.Firstname
};
if (!string.IsNullOrEmpty(x.Middlename))
obj.Middlename = x.Middlename;
return obj;
});
Any better way of doing this
using (var db = new SmartContext())
{
var MyQuery = from idr in db.ID_SB
join tk in db.Track_SB on idr.MB_Track_ID equals tk.MB_TrackID
join talr in db.Track_Album_Reln on tk.MB_TrackID equals talr.MB_Track_ID
join tal in db.Album_SB on talr.MB_AlbumID equals tal.MB_Release_ID
orderby idr.Last_played descending
select new
{
mb = tk.MB_TrackID,
Hash = idr.Hash,
Title = tk.Title,
Album = tal.Album_Name,
Times_Played = idr.Times_played,
Last_Played = idr.Last_played
};
string artist = "";
var list = new[] { new { Hash = "", Title = "", Album = "", Artist = "", Times_Played = "", Last_Played = ""}}.ToList();
list.Clear();
foreach (var q in MyQuery)
{
int i = 0;
var art = db.Track_Artist_Reln.Where(a => a.MB_Track_ID == q.mb);
foreach (var a in art)
{
var tart = db.Artist_SB.Where(ar => ar.MB_Artist_ID == a.MB_ArtistID).Select(ar => ar.Artist_Name);
foreach (var tar in tart)
{ if (i != 0) { artist = artist + ", " + tar; } else { artist = tar; i++; } }
}
list.Add(new
{
Hash = q.Hash.ToString(),
Title = q.Title.ToString(),
Album = q.Album.ToString(),
Artist = artist.ToString(),
Times_Played = q.Times_Played.ToString(),
Last_Played = q.Last_Played.ToString(),
});
}
ListView1.ItemsSource = list;
}
is there any better way for this as it is consuming lot of time
this code serves the purpose
in this i want to retrieve
hash
Title
Albumname
Artist ( containing all the artist for that song in single row field artist)
Times played
Last played
everything i am able to get just by getting join of everything apart from artist name
there are many to may relations
main tables ID_SB, Track_SB, Album_SB, Artist_SB
other are relationship storing the primary keys of both tables
The inner loop can be replaced with using string.Join(…) and .SelectMany() to flatten the nested list (really IEnumerable) into one:
var artist = string.Join(", ",
db.Track_Artist_Reln
.Where(a => a.MB_Track_ID == q.mb)
.SelectMany(a => db.Artist_SB
.Where(ar => ar.MB_Artist_ID == a.MB_ArtistID)
.Select(ar => ar.Artist_Name)));
Instead of converting the enumerable to a List manually you can use .ToList():
var list = MyQuery.Select(q => new{
Hash = q.Hash.ToString(),
Title = q.Title.ToString(),
Album = q.Album.ToString(),
Artist = string.Join(", ",
db.Track_Artist_Reln
.Where(a => a.MB_Track_ID == q.mb)
.SelectMany(a => db.Artist_SB
.Where(ar => ar.MB_Artist_ID == a.MB_ArtistID)
.Select(ar => ar.Artist_Name))),
Times_Played = q.Times_Played.ToString(),
Last_Played = q.Last_Played.ToString(),
}.ToList();