Develop Reference

sorting by using linq comparing two lists?

I have 2 list of items;
IEnumerable<Investigator> investigators = RepositoryContext.InvestigatorRep.GetInvestigators(site.Site.Id, out totalCount);
var NewInvestigators = base.ActivePage.Investigators;
I have 30 items in investigators and 20 items in NewInvesigators, both have property Id, InvId I need to match that.
var all = investigators.Where(b => crInvestigators.Any(a => a.InvestigatorId == b.Id));
I tried this but not worked
I want to create a new list based on matching Id of those two lists. If Id matches get the particular investigator(basically a sort on investigators based on Id existing in NewInvesigators).
I can do it by using for each, but I want to know whether it is possible with linq?
in newinvestigator I have object which is having two property, investigatorId and Name.
In Investigator I have property Id , City , country.
no Name or investigatorId in the investigator list.

You could try something like this:
var result = investigators.Where(inv=>NewInvestigators.Any(ninv=>ninv.id == inv.investigatorId))
.OrderBy(inv=>inv.id);
Another way to get the same result is using a join.
var result = from inv in investigators
join ninv in NewInvestigators
on inv.id equals ninv.investigatorId
order by inv.id
select inv;

C# Linq multiple GroupBy and Select

I have two objects that are linked, States and Cities, so each State has his Cities and each Citie is linked to an State. I also have some Units that have stateID and citieID but they are not linked since i have them only in Json.
What i need is to get only the States and Cities that have Units. I managed to get the first two but was wondering if there was any faster way to do it since i will have to make an update on those datas everyday:
//unitsData have a List of Units objects, this only have stateID, citieID and the unit data
var unitsData = objUnidade.BuscaUnidades();
//unitsState have all units grouped by State, here i also only have stateID and citieID, same data as above
var unitsState = unitsData.GroupBy(x => x.codigoEstado);
//Here is where i make my search inside the unidadesEstados and select only the Estados that i need
var activeStates = unitsState.Select(est => db.States.FirstOrDefault(x => x.ID == est.Key)).Where(state => state != null).ToList();
To do the Cities search i'm doing the same but using an extra foreach, is there a way to make this better ?

You are querying the database multiple times. It's better to use a SELECT ... IN query, which in LINQ looks like:
var units = objUnidad.BuscaUnidades();
var stateIds = units.Select(u => u.codigoEstado).ToList();
var activeStates = db.States.Where(s => stateIds.Contains(s.Id)).ToList();
EDIT: you asked about cities as well. It's more of the same:
var cityIds = units.Select(u => u.codigoCuidad).ToList()
var activeCities = db.Cities.Where(c => cityIds.Contains(c.Id)).ToList();
This solution gives you every city whose ID is referred to by a unit. #StriplingWarrior 's solution will give you every city in (the states that have a unit).

If db.States queries the database, then for each group in unitsState the query will get executed. If the number of states isn't extremely large, you can store them in a list.
var dbStates = db.States.ToList();
var activeStates = unitsState.Select(est => dbStates.FirstOrDefault(x => x.ID == est.Key)).Where(state => state != null).ToList();

LINQ contains between 2 lists

I have a string List and a supplier List<supplier>.
string list contains some searched items and supplier list contains a list of supplier object.
Now I need to find all the supplier names that matches with any of the items in the string List<string>.
this is one of my failed attempts..
var query = some join with the supplier table.
query = query.where(k=>stringlist.contains(k.companyname)).select (...).tolist();
any idea how to do that??
EDIT:
May be my question is not clear enough...I need to find a list of suppliers(not only names,the whole object) where suppliers names matches with the any items in the string list.
If I do
query = query.where(k=>k.companyname.contains("any_string")).select (...).tolist();
it works. but this is not my requirement.
My requirement is a list of string not a single string.

Following query will return distinct suppliers names which exist in list of names:
suppliers.Where(s => stringlist.Contains(s.CompanyName))
.Select(s => s.CompanyName) // remove if you need whole supplier object
.Distinct();
Generated SQL query will look like:
SELECT DISTINCT [t0].[FCompanyName]
FROM [dbo].[Supplier] AS [t0]
WHERE [t0].[CompanyName] IN (#p0, #p1, #p2)
BTW consider to use better names, e.g. companyNames instead of stringlist

You could use Intersect for this (for just matching names):
var suppliersInBothLists = supplierNames
.Intersect(supplierObjects.Select(s => s.CompanyName));
After your EDIT, for suppliers (not just names):
var suppliers = supplierObjects.Where(s => supplierNames.Contains(s.CompanyName));

var matches = yourList.Where(x => stringList.Contains(x.CompanyName)).Select(x => x.CompanyName).ToList();

Either use a join as Tim suggested or you could just use a HashSet directly. This is much more efficient that using .Contains on a List as in some of the other answers.
var stringSet = new HashSet(stringList);
var result = query.Where(q => stringSet.Contains(q.Name));

Linq, filter out multiples

I have written a Search-function in my MVC-project, it matches a database.
The database have the struct like this:
Name - string (The name of the data)
SubName - string (the subname of the data)
SomeData - int (the actual data)
So if i have like 100 posts with a name and a specific subname with different values for the data. and then 100 posts more with the same name but a different subname.
Now when i search the database i use this linq-code;
var names = db.Graphs
.Where(r => r.Name.Contains(term))
.Take(5).Distinct()
.Select(r=> new {label = r.Name});
I thougth that that maby would get med 5 distinct answers, but it dosent...
I get five of the first 100 post, i would like to filter so that i take only uniqe name with subnames. So in the example above i would have revived 2 entrys.
Feel like i have tried everything and failed so any input would be appriciated.

var names = db.Graphs
.Where(r => r.Name.Contains(term))
.GroupBy(s=>s.Name).Take(5)
.Select(r => new { label = r.FirstOrDefault().Name });
You should apply Distinct() before Take().I hope this will help.

Getting records in between two records using Linq

I have a list of objects and need to get the list of records from this list. like I have of Countries and I need to get the list of countries which are in between country with name "Australia" and country "Indonasia", the list will not be sorted.
Am using c#.
I tried to use something like, get the index of first and second and then use that to get the list with a for loop, but would be handy if it can be done in single query.

If you do the following:
var elementsBetween = allElements
.SkipWhile(c => c.Name != "Australia")
.Skip(1) // otherwise we'd get Australia too
.TakeWhile(c => c.Name != "Indonasia");
you'll get the result you want without iterating through the list 3 times.
(This is assuming your countries are e.g. Country items with a Name string property.)
Note that this doesn't sort the countries at all - it's unclear from your question whether you want this or not but it's trivial to add an OrderBy before the SkipWhile.

this should do the job
var query = data.SkipWhile(x => x != "Australia").TakeWhile(x => x != "Indonesia")