I have a query like this:
SELECT [degree_id], [institution_id]
FROM [dbo].[instlist]
where [degree_id]=1
group by institution_id, degree_id
I need to count total rows, so I then use a for loop to get count and then return it. How to convert the query above in Linq? Thanks.
[HttpGet]
public int GetDegreeCountByInstitution(int degreeid)
{
var qry = db.instlist
.GroupBy(g => new { g.degree_id, g.institution_id })
.Select(n => new { degree_id=n.degree_id, institution_id=n.institution_id });
var cnt=0;
for( int i=0; i<qry.ToList().Count; i++)
{
cnt = cnt + 1;
}
return cnt;
}
There is an error on the select statement.
You could apply count for group by;
var result = db.instlist.Where(x => x.degree_id == 1)
.GroupBy(x => new { x.degree_id, x.institution_id })
.Select(g => new
{
degree_id = g.Key.degree_id,
institution_id = g.Key.institution_id,
count = g.Count()//Apply count for grouped records
}).ToList();
Something like:
var q = (from id in instlist
where id.degree_id == 1
select id.degree_id, id.institution_id).Distinct().Count()
Related
I have a table named industries. In this my fields are
workfor_id,
workfor_usr_id,
workfor_industry_id.
With the same values of workfor_id, I have different workfor_industry_id's.
foreach (var k in us){
var ind = dbContext.industries.Where(i => i.workfor_id ==
k.id).Select(i => i).FirstOrDefault();
string ind2 = k.industry;
var industryParts = ind2.Split(',');
var o = (industryParts.Length);
for (c = 0; c < o; c++){
ind.workfor_id = Convert.ToInt16(k.id);
ind.workfor_industry_id = Convert.ToInt16(k.industryid); }
}
To update workfor_industry_id field I have implemented inner loop inside the foreach loop to get the values of workfor_industry_id's.here same record is over loading with different workfor_industry_id's.
can you tell me how to implement this.
UPDATED
This update adds a little more error checking and assumes that -1 is never a valid value for industry_id
short GetShort(string value) {
short returnValue;
value = (value ?? string.Empty).Replace("\"",null);
return short.TryParse(value, out returnValue) ? returnValue : (short)-1;
}
foreach (var k in us){
var id=Convert.ToInt16(k.id);
var toRemove=from i in dbContext.industries
where i.workfor_id == k.id
select i;
var toAdd = from x in (k.industry ?? string.Empty).Split(',')
select new Industry {
workfor_id=id,
workfor_industry_id=GetShort(x)
};
dbContext.industries.DeleteAllOnSubmit(toRemove);
dbContext.industries.InsertAllOnSubmit(toAdd.Where(x=>x.workfor_industry_id != -1));
}
dbContext.SubmitChanges();
I have 2 objects (lists loaded from XML) report and database (showed bellow in code) and i should analyse them and mark items with 0, 1, 2, 3 according to some conditions
TransactionResultCode = 0; // SUCCESS (all fields are equivalents: [Id, AccountNumber, Date, Amount])
TransactionResultCode = 1; // Exists in report but Not in database
TransactionResultCode = 2; // Exists in database but Not in report
TransactionResultCode = 3; // Field [Id] are equals but other fields [AccountNumber, Date, Amount] are different.
I'll be happy if somebody could found time to suggest how to optimize some queries.
Bellow is the code:
THANK YOU!!!
//TransactionResultCode = 0 - SUCCESS
//JOIN on all fields
var result0 = from d in database
from r in report
where (d.TransactionId == r.MovementID) &&
(d.TransactionAccountNumber == long.Parse(r.AccountNumber)) &&
(d.TransactionDate == r.MovementDate) &&
(d.TransactionAmount == r.Amount)
orderby d.TransactionId
select new TransactionList()
{
TransactionId = d.TransactionId,
TransactionAccountNumber = d.TransactionAccountNumber,
TransactionDate = d.TransactionDate,
TransactionAmount = d.TransactionAmount,
TransactionResultCode = 0
};
//*******************************************
//JOIN on [Id] field
var joinedList = from d in database
from r in report
where d.TransactionId == r.MovementID
select new TransactionList()
{
TransactionId = d.TransactionId,
TransactionAccountNumber = d.TransactionAccountNumber,
TransactionDate = d.TransactionDate,
TransactionAmount = d.TransactionAmount
};
//Difference report - database
var onlyReportID = report.Select(r => r.MovementID).Except(joinedList.Select(d => d.TransactionId));
//TransactionResultCode = 1 - Not Found in database
var result1 = from o in onlyReportID
from r in report
where (o == r.MovementID)
orderby r.MovementID
select new TransactionList()
{
TransactionId = r.MovementID,
TransactionAccountNumber = long.Parse(r.AccountNumber),
TransactionDate = r.MovementDate,
TransactionAmount = r.Amount,
TransactionResultCode = 1
};
//*******************************************
//Difference database - report
var onlyDatabaseID = database.Select(d => d.TransactionId).Except(joinedList.Select(d => d.TransactionId));
//TransactionResultCode = 2 - Not Found in report
var result2 = from o in onlyDatabaseID
from d in database
where (o == d.TransactionId)
orderby d.TransactionId
select new TransactionList()
{
TransactionId = d.TransactionId,
TransactionAccountNumber = d.TransactionAccountNumber,
TransactionDate = d.TransactionDate,
TransactionAmount = d.TransactionAmount,
TransactionResultCode = 2
};
//*******************************************
var qwe = joinedList.Select(j => j.TransactionId).Except(result0.Select(r => r.TransactionId));
//TransactionResultCode = 3 - Transaction Results are different (Amount, AccountNumber, Date, )
var result3 = from j in joinedList
from q in qwe
where j.TransactionId == q
select new TransactionList()
{
TransactionId = j.TransactionId,
TransactionAccountNumber = j.TransactionAccountNumber,
TransactionDate = j.TransactionDate,
TransactionAmount = j.TransactionAmount,
TransactionResultCode = 3
};
you may try something like below:
public void Test()
{
var report = new[] {new Item(1, "foo", "boo"), new Item(2, "foo2", "boo2"), new Item(3, "foo3", "boo3")};
var dataBase = new[] {new Item(1, "foo", "boo"), new Item(2, "foo22", "boo2"), new Item(4, "txt", "rt")};
Func<Item, bool> inBothLists = (i) => report.Contains(i) && dataBase.Contains(i);
Func<IEnumerable<Item>, Item, bool> containsWithID = (e, i) => e.Select(_ => _.ID).Contains(i.ID);
Func<Item, int> getCode = i =>
{
if (inBothLists(i))
{
return 0;
}
if(containsWithID(report, i) && containsWithID(dataBase, i))
{
return 3;
}
if (report.Contains(i))
{
return 2;
}
else return 1;
};
var result = (from item in dataBase.Union(report) select new {Code = getCode(item), Item = item}).Distinct();
}
public class Item
{
// You need also to override Equals() and GetHashCode().. I omitted them to save space
public Item(int id, string text1, string text2)
{
ID = id;
Text1 = text1;
Text2 = text2;
}
public int ID { get; set; }
public string Text1 { get; set; }
public string Text2 { get; set; }
}
Note that you need to either implement Equals() for you items, or implement an IEqualityComparer<> and feed it to Contains() methods.
I'm trying to implement a T-SQL equivalent of a where in (select ...) code in LINQ.
This is what I have now:
int contactID = GetContactID();
IEnumerable<string> threadList = (from s in pdc.Messages
where s.ContactID == contactID
group 1 by new { s.ThreadID } into d
select new { ThreadID = d.Key.ThreadID}).ToList<string>();
var result = from s in pdc.Messages
where threadList.Contains(s.ThreadID)
group new { s } by new { s.ThreadID } into d
let maxMsgID = d.Where(x => x.s.ContactID != contactID).Max(x => x.s.MessageID)
select new {
LastMessage = d.Where(x => x.s.MessageID == maxMsgID).SingleOrDefault().s
};
However, my code won't compile due to this error for the ToList():
cannot convert from
'System.Linq.IQueryable<AnonymousType#1>'
to
'System.Collections.Generic.IEnumerable<string>'
Anyone have any suggestions on how to implement this? Or any suggestions on how to simplify this code?
Your query returns a set of anonymous types; you cannot implicitly convert it to a List<string>.
Instead, you should select the string itself. You don't need any anonymous types.
Change it to
var threadList = pdc.Messages.Where(s => s.ContactID == contactID)
.Select(s => s.ThreadID)
.Distinct()
.ToList();
var result = from s in pdc.Messages
where threadList.Contains(s.ThreadID)
group s by s.ThreadID into d
let maxMsgID = d.Where(x => x.ContactID != contactID).Max(x => x.MessageID)
select new {
LastMessage = d.Where(x => x.MessageID == maxMsgID).SingleOrDefault()
};
I want to Enumerate Linq Query. Below i specified example.
EX:
DataTable _slidingDataTable = new DataTable("test");
for(int i=0; i<5;i++)
{
DataRow row = _slidingDataTable.NewRow();
startPosition = DateTime.Now;
for(int i=0; i<5;i++)
{
_slidingDataTable.Columns.Add("TransferTime");
row[columnName] = startPosition ;
_slidingDataTable.Columns.Add("TransferData");
row[columnName] = "Test"+i;
}
_slidingDataTable.Rows.Add(row);
}
var query1 = from myRow in _slidingDataTable.AsEnumerable()
where myRow.Field<DateTime>("TransferTime") == startPosition
select myRow;
This query output should be collection of rows. How to get collection row & iterate.
In your context, query1 is an EnumerableRowCollection<DataRow> because you used _slidingDataTable.AsEnumerable(), and you can iterate over it like so :
foreach (DataRow row in query1)
{
// Do stuff with that row
}
I'm giving you an example by which you can see it and it also includes sum in groupby.
var drdatedisp = from row in dtfullreport.AsEnumerable()
group row by row.Field<string>("Order_Date") into g
select new
{
Order_Date = g.Key,
totalQnty = g.Sum(a => a.Field<int>("Item_Quantity")),
totalTax = g.Sum(a => float.Parse(a.Field<decimal>("TAXAMT").ToString())),
totalAmt = g.Sum(a => float.Parse(a.Field<decimal>("VALAMT").ToString()))
};
DataTable dtdatedisp = new DataTable();
dtdatedisp.Columns.Add("Order_Date");
dtdatedisp.Columns.Add("Item_Quantity");
dtdatedisp.Columns.Add("TAXAMT");
dtdatedisp.Columns.Add("VALAMT");
dtdatedisp.Rows.Clear();
foreach (var g in drdatedisp)
{
DataRow newRow1 = dtdatedisp.NewRow();
newRow1[0] = g.Order_Date;
newRow1[1] = g.totalQnty;
newRow1[2] = String.Format("{0:0.00}", g.totalTax);
newRow1[3] = String.Format("{0:0.00}", g.totalAmt);
dtdatedisp.Rows.Add(newRow1);
}
How can I project the row number onto the linq query result set.
Instead of say:
field1, field2, field3
field1, field2, field3
I would like:
1, field1, field2, field3
2, field1, field2, field3
Here is my attempt at this:
public List<ScoreWithRank> GetHighScoresWithRank(string gameId, int count)
{
Guid guid = new Guid(gameId);
using (PPGEntities entities = new PPGEntities())
{
int i = 1;
var query = from s in entities.Scores
where s.Game.Id == guid
orderby s.PlayerScore descending
select new ScoreWithRank()
{
Rank=i++,
PlayerName = s.PlayerName,
PlayerScore = s.PlayerScore
};
return query.ToList<ScoreWithRank>();
}
}
Unfortunately, the "Rank=i++" line throws the following compile-time exception:
"An expression tree may not contain an assignment operator"
Well, the easiest way would be to do it at the client side rather than the database side, and use the overload of Select which provides an index as well:
public List<ScoreWithRank> GetHighScoresWithRank(string gameId, int count)
{
Guid guid = new Guid(gameId);
using (PPGEntities entities = new PPGEntities())
{
var query = from s in entities.Scores
where s.Game.Id == guid
orderby s.PlayerScore descending
select new
{
PlayerName = s.PlayerName,
PlayerScore = s.PlayerScore
};
return query.AsEnumerable() // Client-side from here on
.Select((player, index) => new ScoreWithRank()
{
PlayerName = player.PlayerName,
PlayerScore = player.PlayerScore,
Rank = index + 1;
})
.ToList();
}
}
Ok, that did the trick. Thanks.
Here is my final code...
Server:
public List<Score> GetHighScores(string gameId, int count)
{
Guid guid = new Guid(gameId);
using (PPGEntities entities = new PPGEntities())
{
var query = from s in entities.Scores
where s.Game.Id == guid
orderby s.PlayerScore descending
select s;
return query.ToList<Score>();
}
}
Client:
void hsc_LoadHighScoreCompleted(object sender, GetHighScoreCompletedEventArgs e)
{
ObservableCollection<Score> list = e.Result;
_listBox.ItemsSource = list.Select((player, index) => new ScoreWithRank()
{
PlayerName = player.PlayerName,
PlayerScore = player.PlayerScore,
Rank = index+=1
}).ToList();
}
You could also make just a slight adjustment to your original code to get it working. Word of caution, if you databind or access the object again, the Rank will increment each time. In those cases the top answer is better.
let Rank = i++
and
Rank.ToString()
Full code:
public List<ScoreWithRank> GetHighScoresWithRank(string gameId, int count)
{
Guid guid = new Guid(gameId);
using (PPGEntities entities = new PPGEntities())
{
int i = 1;
var query = from s in entities.Scores
let Rank = i++
where s.Game.Id == guid
orderby s.PlayerScore descending
select new ScoreWithRank()
{
Rank.ToString(),
PlayerName = s.PlayerName,
PlayerScore = s.PlayerScore
};
return query.ToList<ScoreWithRank>();
}
}
This solution worked for me.
http://www.dotnetfunda.com/articles/article1995-rownumber-simulation-in-linq.aspx
.Select((x, index) => new
{
SequentialNumber = index + 1
,FieldFoo = x.FieldFoo
}).ToList();
List<Emp> Lstemp = GetEmpList();
int Srno = 0;
var columns = from t in Lstemp
orderby t.Name
select new {
Row_number=++Srno,
EmpID = t.ID,
Name = t.Name,
City = t.City
};