I tried many ways but couldn't get the solution.
// linq query to getting 3 fields from table
var listData = (from row in db.table
orderby row.No ascending
select new {
row.Id,
row.No,
row.Type
}).ToList();
I want to add item or value to listData.
try Code:
var listData = (from row in db.table
select new
{
Id= row.Id,
No= row.No,
Type= row.Type
}
).OrderBy(c=>c.No).ToList();
Related
I come from an SQL background and recently started using Firebase for building an ionic shopping cart. This is the database schema:
To retrieve a user's cart, i used the following
var user_id="user1"; // Temporary initialised
var refCart = new Firebase("https://testing.firebaseio.com/cart");
var cart=$firebase(fireBaseData.refCart().child(user_id)).$asArray();
This gives the result:
item1 1
item2 2
item3 5
So tried using foreach()
var refMenu = new Firebase("https://testing.firebaseio.com/menu");
refCart.child(user_id).on("value", function(snapshot) {
snapshot.forEach(function(childSnapshot) {
var item_id = childSnapshot.name();
var qty = childSnapshot.val();
//var data= refMenu.child(item_id).val();
// val is not a function
//var data= refMenu.child(item_id).exportval();
// exportval is not a function
//var data = $firebase (refMenu.child(item_id)). $asArray();
// Give me an array of objects , ie attributes - OK! But what to do next ?
//console.log("DATA",data );
console.log("Item",item_id+" "+qty);
});
});
How can i use item_id to retrieve item details.
Is it the correct way of doing data retrieval from multiple tables?
Update:
Using on() function , i managed to get the item attributes.
refMenu.child(item_id).on("value", function(snapshot) {
console.log("Price",snapshot.val().price);
});
But is there any better implementation for the same.
Is there any better ways to retrieve (from the server side) specific attributes for the item.
Like in SQL
SELECT name,price, ... from menu;
NOTE: .on('event', callback) method will call your callback every time the event is fired.
If you need to retrieve data from a reference once, you should use: .once('event', callback)
NOTE2: snapshot.val() will give you a JSON object that you can assign to a variable
I would do it this way:
refCart.child(user_id).on("value", function(snapshot) {
snapshot.forEach(function(childSnapshot) {
var item_id = childSnapshot.name();
var qty = childSnapshot.val();
refMenu.child(item_id).once("value", function(snapshot) {
var item = snapshot.val()
console.log(item.name +' '+ item.price)
});
});
});
Hope it helps ;)
I know Mongodb for Linq doesn't support group Operation!
So, I found group with Mongo C# driver as group by in LINQ.
I have read mongo-csharp-driver examples, but these are not group examples with filtering.
Please, tell me, thanks.
This is my code.
var Table = DatabaseLinq.GetCollection<Model.Urls>(TableName).FindAll().AsQueryable();
var queryData = (from item in Table
group item by item.Url)
.OrderByDescending(p => p.Sum(x => x.ViewsCount))
.Skip((PageIndex - 1) * PageSize)
.Take(PageSize);
This is my group by, but how can I add filter here?
You can add filter by using Find() instead of .FindAll() method, like this:
var Table = DatabaseLinq.GetCollection<Model.Urls>(TableName)
.Find(Query<Model.Urls>.EQ(x => x.Url, "Ken")).AsQueryable();
var queryData = (from item in Table
group item by item.Url)
.OrderByDescending(p => p.Sum(x => x.ViewsCount))
.Skip((PageIndex - 1) * PageSize)
.Take(PageSize);
var Filter = new BsonDocument("ProductName", "WH-208");
var list = await collection.Find(Filter).ToListAsync();
In the above line 'ProductName' is the KEY and 'WH-208' is the VALUE to search.
Refference
var diaryEntries = (from entry in repository.GetQuery<OnlineDiary.Internal.Model.DiaryEntry>()
.Include("DiaryEntryGradeChangeLog")
.Include("DiaryEntryAction")
join diary in repository.GetQuery<OnlineDiary.Internal.Model.OnlineDiary>()
on entry.DiaryId equals diary.Id
group entry
by diary
into diaryEntriesGroup
select new { Diary = diaryEntriesGroup.Key,
DiaryEntry = diaryEntriesGroup.OrderByDescending(diaryEntry => diaryEntry.DateModified).FirstOrDefault(),
});
This query does not include "DiaryEntryGradeChangeLog" and "DiaryEntryAction" navigation properties, what is wrong in this query?
I have removed join from the query and corrected as per below, and still it populates nothing
var diaryEntries = from entry in repository.GetQuery<OnlineDiary.Internal.Model.DiaryEntry>()
.Include("DiaryEntryGradeChangeLog").Include("DiaryEntryAction")
.Where(e => 1 == 1)
group entry
by entry.OnlineDiary
into diaryEntryGroups
select
new { DiaryEntry = diaryEntryGroups.OrderByDescending(diaryEntry => diaryEntry.DateModified).FirstOrDefault() };
It will not. Include works only if the shape of the query does not change (by design). If you use this query it will work because the shape of the query is still same (OnlineDiary.Internal.Model.DiaryEntry):
var diaryEntries = (from entry in repository.GetQuery<OnlineDiary.Internal.Model.DiaryEntry>()
.Include("DiaryEntryGradeChangeLog")
.Include("DiaryEntryAction");
But once you use manual join, grouping or projection (select new { }) you have changed the shape of the query and all Include calls are skipped.
Edit:
You must use something like this (untested) to get related data:
var diaryEntries = from entry in repository.GetQuery<OnlineDiary.Internal.Model.DiaryEntry>()
group entry by entry.OnlineDiary into diaryEntryGroups
let data = diaryEntryGroups.OrderByDescending(diaryEntry => diaryEntry.DateModified).FirstOrDefault()
select new {
DiaryEntry = data,
GradeChangeLog = data.DiaryEntryGradeChangeLog,
Action = data.DiaryEntryAction
};
or any similar query where you manually populate property for relation in projection to anonymous or unmapped type.
I have an entity set called Entities which has a field Name and a field Version. I wish to return the object having the highest version for the selected Name.
SQL wise I'd go
Select *
from table
where name = 'name' and version = (select max(version)
from table
where name = 'name')
Or something similar. Not sure how to achieve that with EF. I'm trying to use CreateQuery<> with a textual representation of the query if that helps.
Thanks
EDIT:
Here's a working version using two queries. Not what I want, seems very inefficient.
var container = new TheModelContainer();
var query = container.CreateQuery<SimpleEntity>(
"SELECT VALUE i FROM SimpleEntities AS i WHERE i.Name = 'Test' ORDER BY i.Version desc");
var entity = query.Execute(MergeOption.OverwriteChanges).FirstOrDefault();
query =
container.CreateQuery<SimpleEntity>(
"SELECT VALUE i FROM SimpleEntities AS i WHERE i.Name = 'Test' AND i.Version =" + entity.Version);
var entity2 = query.Execute(MergeOption.OverwriteChanges);
Console.WriteLine(entity2.GetType().ToString());
Can you try something like this?
using(var container = new TheModelContainer())
{
string maxEntityName = container.Entities.Max(e => e.Name);
Entity maxEntity = container.Entities
.Where(e => e.Name == maxEntityName)
.FirstOrDefault();
}
That would select the maximum value for Name from the Entities set first, and then grab the entity from the entity set that matches that name.
I think from a simplicity point of view, this should be same result but faster as does not require two round trips through EF to sql server, you always want to execute query as few times as possible for latency, as the Id field is primary key and indexed, should be performant
using(var db = new DataContext())
{
var maxEntity = db.Entities.OrderByDecending(x=>x.Id).FirstOrDefault()
}
Should be equivalent of sql query
SELECT TOP 1 * FROM Entities Order By id desc
so to include search term
string predicate = "name";
using(var db = new DataContext())
{
var maxEntity = db.Entities
.Where(x=>x.Name == predicate)
.OrderByDecending(x=>x.Id)
.FirstOrDefault()
}
I think something like this..?
var maxVersion = (from t in table
where t.name == "name"
orderby t.version descending
select t.version).FirstOrDefault();
var star = from t in table
where t.name == "name" &&
t.version == maxVersion
select t;
Or, as one statement:
var star = from t in table
let maxVersion = (
from v in table
where v.name == "name"
orderby v.version descending
select v.version).FirstOrDefault()
where t.name == "name" && t.version == maxVersion
select t;
this is the easiest way to get max
using (MyDBEntities db = new MyDBEntities())
{
var maxReservationID = _db .LD_Customer.Select(r => r.CustomerID).Max();
}
I am using Entitry Framework 4.1 and I am struggling to understand how the convert the below query which uses joins and aggregate methods to a Linq to Entities call in the DomainService.
SELECT tblTime.Period As Timeline, COUNT(tblEngineeringDashboard_ItemList.ID) AS Items
FROM tblEngineeringDashboard_ItemList INNER JOIN
tblTime ON tblEngineeringDashboard_ItemList.TimeID = tblTime.ID
GROUP BY tblTime.Period
ORDER BY tblTime.Period
Can anyone provide help.
Possible Solution
Dim var = From i In ObjectContext.tblEngineeringDashboard_ItemList
Join t In ObjectContext.tblTimes On i.TimeID Equals t.ID
Group By i.TimeID Into Group
Select DateStart = (From n In ObjectContext.tblTimes Where n.ID = TimeID Select n.Period), PartCount = Group.Count
Phil
The first thing which comes to mind is:
var q = from t in Context.Time
group t by t.Period into g
orderby g.Key
select new
{
Timeline = g.Key,
Items = (from ti in g
from il in ti.ItemList // or whatever the property for the navigation to tblEngineeringDashboard_ItemList is called
select il).Count()
};
However, the original SQL had an INNER JOIN, which would reject tblTime records without any matching records in tblEngineeringDashboard_ItemList. So you may want:
var q = from t in Context.Time
where t.ItemList.Any()
group t by t.Period into g
orderby g.Key
select new
{
Timeline = g.Key,
Items = (from ti in g
from il in ti.ItemList // or whatever the property for the navigation to tblEngineeringDashboard_ItemList is called
select il).Count()
};
You can also flip the query around:
var q = from i in Context.EngineeringDashboardItemList
where i.Time != null
group i by i.Time.Period into g
orderby g.Key
select new
{
Timeline = g.Key,
Items = g.Count()
};
Does this work?
tblEngineeringDashboard_ItemList
.Join(tblTime,ed => ed.TimeID ,t => t.ID, (ed,t) => new{ed,t})
.GoupBy(g => g.t.Period)
.Select(s => new
{
Timeline = s.Key,
Items = s.Count()
}
)
.OrderBy(o => o.Timeline)
While converting from sql to linq isn't an ideal approach (you should think directly in linq, translating your need to a linq query), the query you posted is rather simple.
var grouped = tblTime.OrderBy(c => c.Period).GroupBy(c => c.Period).Select(c =>
new {
timeline = c.Key,
count = c.SelectMany(x => x.tblEngineeringDashboard).Count()
});
*Edit: There, fixed. Everything on the L2E engine.
This provided that there are correct foreign keys between the tables (thus you don't have to declare the join manually).