I have an list of DemoInfo object with list of StatInfo object in it as below-:
public class DemoInfo
{
public string name;
public List<StatInfo> stat;
public string workLocation;
}
Further StatInfo is below object
public class StatInfo
{
public string contact;
public DateTime createdDate;
public string action;
}
I need to orderby list of DemoInfo by createdDate
How can I do that in Linq?
Your problem is because you haven't got a proper specification
I need to orderby list of DemoInfo by createdDate
You can't do that, becuase a DemoInfo has no CreatedDate. If you assume that a DemoInfo was created the day that it got its first StatInfo then you could use the oldest StatInfo to order:
I need to order my sequence of DemoInfo in ascending order by its creation date, which is defined as the date of its oldest StatInfo.
This still has a problem: what is the CreatedDate of a DemoInfo after all its StatInfos are removed? And removing the oldest StatInfo of a DemoInfo with many StatInfos suddenly changes the CreatedDate of the DemoInfo.
But let's assume that that's no problem for you, and you want all DemoInfo without any StatInfo last in your result (because they will get their CreationDate in future, when it gets its first StatInfo. Your query will be like:
var result = myDemoInfos.Select(demoInfo => new
{
DemoInfo = demoInfo,
// if the demoInfo has a non-null stat and a non-empty stat
// order it by ascending StatInfo.CreatedDate, and take the first
// otherwise use DateTime.MaxValue (Created in far future)
CreationDate = ( (demoInfo.stat != null) && (demoInfo.stat.Any()) ?
demoInfo.Stat
.Select(statInfo => createdDate)
.OrderBy(createdDate => createdDate)
.First() : // you know there is a first, you just checked Any()
DateTime.MaxValue, // if there is no First, take far future
})
.OrderBy(item => item.CreationDate)
.Select(item => item.DemoInfo);
This can be smarter: you don't have to sort all createdDates, you only need the createdDate with the smallest TickCount:
TickCount = ( (demoInfo.stat != null) && (demoInfo.stat.Any()) ?
demoInfo.stat.Select(statInfo => statInfo.createdDate.TickCount).Min() :
DateTime.MaxValue.TickCount,
And sort by ascending TickCount
Related
I have a table (or entity) named Cases. There is another table CaseStatus_Lookup and the primary key of this table is a foreign key in the Cases table.
What I want to do is: For every status type I want the number of count of cases. For e.g. if status = in progress , I want to know how many cases are in that status.
one other thing: I also want to filter the Cases based on UserID.
I tried several ways in LINQ but could not get vary far. I was wondering if someone could help.
try Linq .GroupBy
am assuming your entity structure
suppose your Case Entity is like
public class Case
{
public int Id{get;set;}
public int CaseStatusId{get;set;}
public int UserId{get;set;}
//navigational fields
public virtual CaseStatus CaseStatus {get;set;}
}
and suppose your CaseStatus entity is like:
public class CaseStatus
{
public int Id{get;set;}
public string Name{get;set;}
//navigational fields..
public virtual ICollection<Case> Cases{get;set;}
}
then you can do this:
using (myDbContext db = new myDbContext())
{
var query = db.Cases.GroupBy(case => case.CaseStatus.Name)
.Select(group =>
new {
Name = group.Key,
Cases= group.OrderBy(x => x.Id),
Count= group.Count()
}
).ToList();
//query will give you count of cases grouped by CaseStatus.
}
similarly you can further filter your result based on userId.
Start to explore about Linq .GroupBy
You need a function that returns the sum and takes the status as parameter :- something like below.
MyCaseStatusEnum caseStatus; //Pass your required status
int caseCount = myCases
.Where(r => r.Status == caseStatus)
.GroupBy(p => p.Status)
.Select(q => q.Count()).FirstOrDefault<int>();
I have an IEnumerable<MyObject> collection, with N MyObject elements.
MyObject is a class with a Title, a Description and an ID (as string).
I'd like to have my collection with distinct list of MyObject, due to the ID field.
So if 2 MyObject have got the same ID, one should be deleted (don't care which, I need unique ID).
How can I do it with LINQ?
Tried :
myList = myList.GroupBy(o => o.ID);
but seems I need a cast?
You can implement a custom IEqualityComparer<MyObject>. Then you can use Enumerable.Distinct to filter out duplicates.
class DistinctIdComparer : IEqualityComparer<MyObject> {
public bool Equals(MyObject x, MyObject y) {
return x.Id == y.Id;
}
public int GetHashCode(MyObject obj) {
return obj.Id.GetHashCode();
}
}
Now it's simple:
IEnumerable<MyObject> distinct = myObjects.Distinct(new DistinctIdComparer());
Or you can use Enumerable.GroupBy what is even simpler:
distinct = myObjects.GroupBy(o => o.ID)
.Select(g => g.First());
If you wants only unique id then you can try.
var uniqueIds = myObjects.Select(x=>x.ID).Distinct();
Or for Unique ID Objects
List<MyObject> objs = new List<MyObject> ();
myObjects.ForEach(x=>{
if(objs.Find(y=>y.ID == x.ID)== null)
objs.Add(x);
});
Lets say I have a generic list of the the following objects:
public class Supermarket
{
public string Brand { get; set; }
public string Suburb { get; set; }
public string State { get; set; }
public string Country { get; set; }
}
So using a List<Supermarket> which is populated with many of these objects with different values I am trying to:
Select the distinct Suburb properties from a
superset of Supermarket objects contained in a List<Supermarket> (say this superset contains 20
distinct Suburbs).
Join the Distinct List of Suburbs above to another set of aggregated and counted Suburbs obtained by a LINQ query to a different, smaller list of List<Supermarket>
The distinct items in my superset are:
"Blackheath"
"Ramsgate"
"Penrith"
"Vaucluse"
"Newtown"
And the results of my aggregate query are:
"Blackheath", 50
"Ramsgate", 30
"Penrith", 10
I want to join them to get
"Blackheath", 50
"Ramsgate", 30
"Penrith", 10
"Vaucluse", 0
"Newtown", 0
Here is what I have tried so far:
var results = from distinctSuburb in AllSupermarkets.Select(x => x.Suburb).Distinct()
select new
{
Suburb = distinctSuburb,
Count = (from item in SomeSupermarkets
group item by item.Suburb into aggr
select new
{
Suburb = aggr.Key,
Count = aggr.Count()
} into merge
where distinctSuburb == merge.Suburb
select merge.Count).DefaultIfEmpty(0)
} into final
select final;
This is the first time I have had to post on Stack Overflow as its such a great resource, but I can't seem to cobble together a solution for this.
Thanks for your time
EDIT: OK So I solved this a short while after the initial post. The only thing I was missing was chaining a call to .ElementAtOrDefault(0) after the call to .DefaultIfEmpty(0). I also verifed that using .First() instead of .DefaultIfEmpty(0) as Ani pointed out worked, The correct query is as follows:
var results = from distinctSuburb in AllSupermarkets.Select(x => x.Suburb).Distinct()
select new
{
Suburb = distinctSuburb,
Count = (from item in SomeSupermarkets
group item by item.Suburb into aggr
select new
{
Suburb = aggr.Key,
Count = aggr.Count()
} into merge
where distinctSuburb == merge.Suburb
select merge.Count).DefaultIfEmpty(0).ElementAtOrDefault(0)
} into final
select final;
LASTLY: I ran Ani's code snippet and confirmed that it ran successfully, so both approaches work and solve the original question.
I don't really understand the assumed equivalence between State and Suburb (where distinctSuburb == merge.State), but you can fix your query adding a .First() after the DefaultIfEmpty(0) call.
But here's how I would write your query: using a GroupJoin:
var results = from distinctSuburb in AllSupermarkets.Select(x => x.Suburb).Distinct()
join item in SomeSupermarkets
on distinctSuburb equals item.Suburb
into suburbGroup
select new
{
Suburb = distinctSuburb,
Count = suburbGroup.Count()
};
I had the following query using normal linq and it was working great (using anonymous type),
var result = from s in Items
group s by s.StartTime into groupedItems
select new {groupedItems.Key, Items= groupedItems.OrderBy(x => x.Name) };
But using Dynamic Linq I cannot get it to order by within the groupby.
result = Items.GroupBy("StartTime", "it").OrderBy("Name");
It states the Name isn't available. It is worth noting that if I take my OrderBy off, everything works great but items inside each "Key" are not ordered.
This is a good question!
I simulated your situation by creating a class called Item.
public class Item
{
public DateTime StartTime { get; set; }
public string Name { get; set; }
}
and then created a basic list of items to do the groupby.
List<Item> Items = new List<Item>()
{
new Item() { StartTime = DateTime.Today, Name = "item2"},
new Item() { StartTime = DateTime.Today, Name = "item1"},
new Item() { StartTime = DateTime.Today.AddDays(-1), Name = "item3"},
};
Now the big difference in the 2 queries is where the order by is being performed. In the first query, when you perform groupedItems.OrderBy(x => x.Name) its being performed on a IGrouping<DateTime,Item> or a single entry as it iterates through all the groupings.
In the second query, the orderby is being performed after the fact. This means you're doing an orderby on a IEnumerable<IGrouping<DateTime,Item>> because the iterations have already happened.
Since Microsoft was nice they added something to help deal with this for expressions. This overload allows you to specify the item returned as it iterates through the collection. Here's an example of the code:
var expressionResult = Items.GroupBy(x => x.StartTime,
(key, grpItems) => new { key, Items = grpItems.OrderBy(y => y.Name) });
The second part of the GroupBy you can specify a lambda expression that takes a key and a grouping of items under that key and return an entry that you specify, which is the same as you're doing in the original query.
Hope this helps!
How can I select a list of column values from a result set (as distinct) and put into a list?
class T {int id; string name;}
-- Controller...
var query = #"exec someStoredProc";
IEnumerable<T> bb =
db2.Database.SqlQuery<T>(query);
// Something like???:
List<string> Names = bb.SelectDistinct("name"); // returns distinct list of names from result set
Since you just need the distinct list of names, you can project to the name property and the just use Distinct() :
List<string> Names = bb.Select( x=> x.name)
.Distinct()
.ToList();
This requires that you make the name property public, also I would rethink your class name T, how about CustomerName (or whatever else is expressive enough so you know what it means) ?
public class CustomerName
{
public int id{get;set;}
public string name {get;set;}
}