LINQ query with a where condition containing - c#

I am just learning LINQ and I have come across and issue Im not sure how to do in LINQ.
string numbers = "1,3,4,5";
string[] outletsInaStringArray = outlets.Split(',');
List<string> numbersAsAList = outletsInaStringArray.ToList();
I have a field in my database which holds a number. I only want to select the lines WHERE the number in the database is IN the line list of numbers "1,3,4,5" (these numbers are just examples).
Thanks in advance
I have looked at Tim and James answers and also looked at the line that James has sent. Im still a bit confused.....Sorry. Below is my actual code. It compiles but does not work
string outlets = "1,3,4,5"
string[] outletsNeeded = outlets.Split(',');
List<string> outletsNeededList = outletsNeeded.ToList();
DashboardEntities1 db = new DashboardEntities1();
var deptSalesQuery = (
from d in db.DashboardFigures
where (d.TypeOfinformation == "DEPTSALES") && (outletsNeeded.ToString().Contains(d.OutletNo.ToString()))
select new DeptSales
{
Dn = (int)d.Number,
Dnm = "Mens",
On = d.OutletNo,
Qs = (double)d.Value_4,
Se = (double)d.Value_2,
Si = (double)d.Value_3
}
);
In the DASHBAORDFIGURES table in SQL I have 2 records where the outlets number = 1, and therefore should have come up with two records.
Sorry if this is a simple thing, its just new to me and its frustrating.


You can use Contains as tagged:
var query = db.Table
.Where(x => outletsInaStringArray.Contains(x.Number) && x.information == "SALES");
that was method syntax, if you prefer query syntax:
var query = from figure in db.Figures
where outletsInaStringArray.Contains(figure.number)
&& figure.information == "SALES"
select figure;
But the column number is int, the List<string> stores strings, maybe your LINQ provider does not support .Contains(figure.ToString()). Then convert the strings to int first:
List<int> outletsNeededList = outletsNeeded.Select(int.Parse).ToList();


The answer that Tim provided is one method. Linq and lambda are interchangeable. Have a look at the following posting as well. Link
var result = from x in db.Table.ToList()
where outletsInaStringArray.Contains(x.Number)
select x;
Also have a look the following as it offers a very similar solution to the one you are looking for:
Link


As per i understand, you want to fetch data in similar way as IN (SQL) clause does it.
SELECT <Field_List>
FROM Table
WHERE IntegerField IN (1,2,4,5)
But i'm wondering why do you want to do it that way, when you can join data and get only matches. The worse is that you're trying to mix different data type and pass comma delimited text as a set of integers (i may be wrong):
SELECT <Field_List>
FROM Table
WHERE IntegerField IN ("1,2,4,5")
Above query won't execute, because the set of integers is "packed" into comma delimited string. To be able to execute that query, a conversion between data types must be done. Numbers in a string have to be converted to a set of integers (using user define split function or Common Table Expression):
;WITH CTE AS
(
--here convertion occurs
)
SELECT t2.<Field_List>
FROM CTE As t1 INNER JOIN TableName AS t2 ON t1.MyNumber = t2.IntegerField
Linq + any programming language is more flexible. You can build a list of integers (List) to build query.
See simple example:
void Main()
{
List<MyData> data = new List<MyData>{
new MyData(1,10),
new MyData(2, 11),
new MyData(5, 12),
new MyData(8, 13),
new MyData(12, 14)
};
//you're using comma delimited string
//string searchedNumbers = "1,3,4,5";
//var qry = from n in data
// join s in searchedNumbers.Split(',').Select(x=>int.Parse(x)) on n.ID equals s
// select n;
//qry.Dump();
List<int> searchedNumbers = new List<int>{1,2,4,5};
var qry = from n in data
join s in searchedNumbers on n.ID equals s
select n;
qry.Dump();
}
// Define other methods and classes here
class MyData
{
private int id = 0;
private int weight = 0;
public MyData(int _id, int _weight)
{
id = _id;
weight = _weight;
}
public int ID
{
get{return id;}
set {id = value;}
}
public int Weight
{
get{return weight;}
set {weight = value;}
}
}
Result:
ID Weight
1 10
5 12
Cheers
Maciej


Thank you all iv now got it to work using all your suggestions
the final code that works is as follows
DeptSales myDeptSales = new DeptSales(); // Single department
List<DeptSales> myDeptSalesList = new List<DeptSales>(); // List of Departments
DashboardEntities1 db = new DashboardEntities1();
var deptSalesQuery = from d in db.DashboardFigures
join s in outlets.Split(',').Select(x => int.Parse(x)) on d.OutletNo equals s
where (d.TypeOfinformation == "DEPTSALES")
select new DeptSales
{
Dn = (int)d.Number,
Dnm = "Mens",
On = d.OutletNo,
Qs = (double)d.Value_4,
Se = (double)d.Value_2,
Si = (double)d.Value_3
};
Thanks once again.

Related

How to return nested object using Generic method and Dapper [duplicate]

I'm currently using Entity Framework for my db access but want to have a look at Dapper. I have classes like this:
public class Course{
public string Title{get;set;}
public IList<Location> Locations {get;set;}
...
}
public class Location{
public string Name {get;set;}
...
}
So one course can be taught at several locations. Entity Framework does the mapping for me so my Course object is populated with a list of locations. How would I go about this with Dapper, is it even possible or do I have to do it in several query steps?

Alternatively, you can use one query with a lookup:
var lookup = new Dictionary<int, Course>();
conn.Query<Course, Location, Course>(#"
SELECT c.*, l.*
FROM Course c
INNER JOIN Location l ON c.LocationId = l.Id
", (c, l) => {
Course course;
if (!lookup.TryGetValue(c.Id, out course))
lookup.Add(c.Id, course = c);
if (course.Locations == null)
course.Locations = new List<Location>();
course.Locations.Add(l); /* Add locations to course */
return course;
}).AsQueryable();
var resultList = lookup.Values;
See here https://www.tritac.com/blog/dappernet-by-example/

Dapper is not a full blown ORM it does not handle magic generation of queries and such.
For your particular example the following would probably work:
Grab the courses:
var courses = cnn.Query<Course>("select * from Courses where Category = 1 Order by CreationDate");
Grab the relevant mapping:
var mappings = cnn.Query<CourseLocation>(
"select * from CourseLocations where CourseId in #Ids",
new {Ids = courses.Select(c => c.Id).Distinct()});
Grab the relevant locations
var locations = cnn.Query<Location>(
"select * from Locations where Id in #Ids",
new {Ids = mappings.Select(m => m.LocationId).Distinct()}
);
Map it all up
Leaving this to the reader, you create a few maps and iterate through your courses populating with the locations.
Caveat the in trick will work if you have less than 2100 lookups (Sql Server), if you have more you probably want to amend the query to select * from CourseLocations where CourseId in (select Id from Courses ... ) if that is the case you may as well yank all the results in one go using QueryMultiple

No need for lookup Dictionary
var coursesWithLocations =
conn.Query<Course, Location, Course>(#"
SELECT c.*, l.*
FROM Course c
INNER JOIN Location l ON c.LocationId = l.Id
", (course, location) => {
course.Locations = course.Locations ?? new List<Location>();
course.Locations.Add(location);
return course;
}).AsQueryable();

I know I'm really late to this, but there is another option. You can use QueryMultiple here. Something like this:
var results = cnn.QueryMultiple(#"
SELECT *
FROM Courses
WHERE Category = 1
ORDER BY CreationDate
;
SELECT A.*
,B.CourseId
FROM Locations A
INNER JOIN CourseLocations B
ON A.LocationId = B.LocationId
INNER JOIN Course C
ON B.CourseId = B.CourseId
AND C.Category = 1
");
var courses = results.Read<Course>();
var locations = results.Read<Location>(); //(Location will have that extra CourseId on it for the next part)
foreach (var course in courses) {
course.Locations = locations.Where(a => a.CourseId == course.CourseId).ToList();
}

Sorry to be late to the party (like always). For me, it's easier to use a Dictionary, like Jeroen K did, in terms of performance and readability. Also, to avoid header multiplication across locations, I use Distinct() to remove potential dups:
string query = #"SELECT c.*, l.*
FROM Course c
INNER JOIN Location l ON c.LocationId = l.Id";
using (SqlConnection conn = DB.getConnection())
{
conn.Open();
var courseDictionary = new Dictionary<Guid, Course>();
var list = conn.Query<Course, Location, Course>(
query,
(course, location) =>
{
if (!courseDictionary.TryGetValue(course.Id, out Course courseEntry))
{
courseEntry = course;
courseEntry.Locations = courseEntry.Locations ?? new List<Location>();
courseDictionary.Add(courseEntry.Id, courseEntry);
}
courseEntry.Locations.Add(location);
return courseEntry;
},
splitOn: "Id")
.Distinct()
.ToList();
return list;
}

Something is missing. If you do not specify each field from Locations in the SQL query, the object Location cannot be filled. Take a look:
var lookup = new Dictionary<int, Course>()
conn.Query<Course, Location, Course>(#"
SELECT c.*, l.Name, l.otherField, l.secondField
FROM Course c
INNER JOIN Location l ON c.LocationId = l.Id
", (c, l) => {
Course course;
if (!lookup.TryGetValue(c.Id, out course)) {
lookup.Add(c.Id, course = c);
}
if (course.Locations == null)
course.Locations = new List<Location>();
course.Locations.Add(a);
return course;
},
).AsQueryable();
var resultList = lookup.Values;
Using l.* in the query, I had the list of locations but without data.

Not sure if anybody needs it, but I have dynamic version of it without Model for quick & flexible coding.
var lookup = new Dictionary<int, dynamic>();
conn.Query<dynamic, dynamic, dynamic>(#"
SELECT A.*, B.*
FROM Client A
INNER JOIN Instance B ON A.ClientID = B.ClientID
", (A, B) => {
// If dict has no key, allocate new obj
// with another level of array
if (!lookup.ContainsKey(A.ClientID)) {
lookup[A.ClientID] = new {
ClientID = A.ClientID,
ClientName = A.Name,
Instances = new List<dynamic>()
};
}
// Add each instance
lookup[A.ClientID].Instances.Add(new {
InstanceName = B.Name,
BaseURL = B.BaseURL,
WebAppPath = B.WebAppPath
});
return lookup[A.ClientID];
}, splitOn: "ClientID,InstanceID").AsQueryable();
var resultList = lookup.Values;
return resultList;

There is another approach using the JSON result. Even though the accepted answer and others are well explained, I just thought about an another approach to get the result.
Create a stored procedure or a select qry to return the result in json format. then Deserialize the the result object to required class format. please go through the sample code.
using (var db = connection.OpenConnection())
{
var results = await db.QueryAsync("your_sp_name",..);
var result = results.FirstOrDefault();
string Json = result?.your_result_json_row;
if (!string.IsNullOrEmpty(Json))
{
List<Course> Courses= JsonConvert.DeserializeObject<List<Course>>(Json);
}
//map to your custom class and dto then return the result
}
This is an another thought process. Please review the same.

perform inequality comparisons to alphanumeric data in linq

Need help with linq query. I have a column which contains alphanumeric data in it and I want to extract numbers and perform mathematical comparisons. For example >,< etc.
So the data would be like: JS20, MRR12, DEEN2 etc.
I tried converting it to Int but it fails
var TheData = (from p in db.data.Where(l => Convert.ToInt16(l.TextAndNumber) <= 10)
group p by p.Names into g
select g.Key).ToList();
return Json(new { data = TheData });

Try something like this:
(from row in db.data
let digits = new String(row.TextAndNumber.Where(Char.IsDigit).ToArray())
let number = Int64.Parse(digits)
where number < 10
select row.Names
).Distinct();

You need to extract the numbers from the string before applying your conversion.
List<string> data = new List<string> { "JS20", "MRR112", "DEEN2" };
var TheData = data.Where(d => Convert.ToInt32(new string(d.Where(char.IsNumber).ToArray())) <= 10);
This returns DEEN2.

LINQ query optimization

I retrieve data from two different repositories:
List<F> allFs = fRepository.GetFs().ToList();
List<E> allEs = eRepository.GetEs().ToList();
Now I need to join them so I do the following:
var EFs = from c in allFs.AsQueryable()
join e in allEs on c.SerialNumber equals e.FSerialNumber
where e.Year == Convert.ToInt32(billingYear) &&
e.Month == Convert.ToInt32(billingMonth)
select new EReport
{
FSerialNumber = c.SerialNumber,
FName = c.Name,
IntCustID = Convert.ToInt32(e.IntCustID),
TotalECases = 0,
TotalPrice = "$0"
};
How can I make this LINQ query better so it will run faster? I would appreciate any suggestions.
Thanks

Unless you're able to create one repository that contains both pieces of data, which would be a far preferred solution, I can see the following things which might speed up the process.
Since you'r always filtering all E's by Month and Year, you should do that before calling ToList on the IQueryable, that way you reduce the number of E's in the join (probably considerably)
Since you're only using a subset of fields from E and F, you can use an anonymous type to limit the amount of data to transfer
Depending on how many serialnumbers you're retrieving from F's, you could filter your E's by serials in the database (or vice versa). But if most of the serialnumbers are to be expected in both sets, that doesn't really help you much further
Reasons why you might not be able to combine the repositories into one are probably because the data is coming from two separate databases.
The code, updated with the above mentioned points 1 and 2 would be similar to this:
var allFs = fRepository.GetFs().Select(f => new {f.Name, f.SerialNumber}).ToList();
int year = Convert.ToInt32(billingYear);
int month = Convert.ToInt32(billingMonth);
var allEs = eRepository.GetEs().Where(e.Year == year && e.Month == month).Select(e => new {e.FSerialNumber, e.IntCustID}).ToList();
var EFs = from c in allFs
join e in allEs on c.SerialNumber equals e.FSerialNumber
select new EReport
{
FSerialNumber = c.SerialNumber,
FName = c.Name,
IntCustID = Convert.ToInt32(e.IntCustID),
TotalECases = 0,
TotalPrice = "$0"
};

how to only query newest version?

The following query gives me a barcode, version no of that barcode and an appcode. I would need the query to filter out duplicate barcodes and only keep the highest version number of that barcode.
I've been thinking along the way of merging the barcode field and the version field and only keep the highest but that seems dirty. Is there a cleaner solution?
select Barcode, MAX(versionNo) vn, Appcode from Mailsort
where Created between '01/26/2011' and '01/27/2011'
group by Barcode, AppCode;
The reason for this query is to get a LINQ statement.This does a count for every appcode regardless of the barcodes or the version at thye moment.
var results = from p in dataContext.GetTable<mailsortEntity>()
where p.Created > datetime && p.Created < datetime.AddDays(1)
group p by new { p.AppCode } into g
select new AppCodeCountEntity
{
AppCode = g.Key.AppCode,
Count = g.Count()
};
Is there a better solution than this LINQ code above?

var maxQuery =
from rh in MailSort
group rh by rh.BarCode into latest
select new { BarCode = latest.Key, MaxVersion = latest.Max(l => l.Version) }
;
var query =
from rh2 in MailSort
join max in maxQuery on new {rh2.BarCode, Version = rh2.Version }
equals new { max.BarCode, Version = max.MaxVersion }
select new { rh2.BarCode, rh2.Version, rh2.AppCode }
;
var barCodes = query.ToList();

Group Number in a LINQ Group by Query

I've been using 101 LINQ Samples to get my feet wet using LINQ. It's been a good first resource, but I can't see an example there of what I currently need.
I just need to associate a sequential group number with each group. I have a working solution:
var groups =
from c in list
group c by c.Name into details
select new { Name = details.Key, DetailRecords = details };
int groupNumber = 0;
foreach (var group in groups)
{
//
// process each group and it's records ...
//
groupNumber++;
}
But, I'm sure it's possible to use LINQ to also generate the groupNumber. How?

This depends on your exact needs, but you can use:
var groupArray = groups.ToArray();
Similarly, you can use ToList. These data structures are sequential, and each group has an index.
If you do need the index on the object you create, another option is to use Select:
list.GroupBy(c => c.Name)
.Select((details, ind) =>
new
{
Name = details.Key,
DetailRecords = details,
Index = ind
});

this should do the trick:
int groupNumber = 0;
var groups =
from c in list
group c by c.Name into details
select new { Name = details.Key, DetailRecords = details, grpNum = groupNumber++};

if it's just a sequential group number, just use the Count() method on your IEnumerable.
var groups =
from c in list
group c by c.Name into details
select new {Name = details.Key, DetailRecords = details};
for(int i = 0; i < groups.Count(); i++)
{
//Process Records
}
Then, if you need the specific group number, you can just grab i.

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