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;

List variable inside a query Linq

I have created a variable that returns a list ids of menus from the database. I have then put the variable in another query that returns meals in a list. My issue is that I keep on recieving the error Cannot implicitly convert type System.Collections.Generic.List<int?> to int?
var getmenuids = (from r in db.Menus
where (r.Restaurantid == currentrestaurant)
select r.Id).ToList();
var meals = db.Meals.Where(r => r.MenuID = getmenuids).ToList();

You're having an issue because you're using == (comparing a single element to a list) instead of Contains() (searching for the an element in the list).
var meals = db.Meals.Where(r => getmenuids.Contains(r.MenuID)).ToList();
You could combine these too.. something like this:
var meals = (from meal in db.Meals
join menu in db.Menus on meal.MenuID equals menu.Id
where menu.Restaurantid == currentrestaurant
select meal).ToList();

The problem here is that getmenuids is a collection of int? values but you compare it to r.MenuID which is typed to int?. To fix this you need to search getmenuids for r.MenuId
db.Meals.Where(r => getmenuids.Contains(r.MenuID)).ToList();

You are comparing the list with MenuID. getmenuids is a list.
r.MenuID = getmenuids

Compare id's of objects in two lists and get the list of objects that includes objects with ids occurring in both of them

I have struggled with it for a long time. I have two collections: MyRepository.All and MyCollection, both holds the collection of objects which has ID property. I need to get result of list of objects from MyRepository.All what contains only objects which id's are equal to MyCollection's objects'ids.
ICollection MyCollection // as parameter to method
var result = MyRepository.All.Where(r=>r.id==MyCollection.???.id).ToList();
i need to replace ??? with some linq to get this done.
ive tried different where and select caluses, excist and intersect and so on..

from a in MyRepository.All
join m in MyCollection on a.Id equals m.Id
select a

Cache the ids of MyCollection into a HashSet.
Than you can retrieve your result with a Where clause like this :
var myIdSets = new HashSet(MyCollection.Select(c => c.Id));
var result = MyRepository.All.Where(r=> myIdSets.Contains(r.id)).ToList();

var result = (from r in MyRepository.All
join r2 in MyCollection on r.id equals r2.id
select r).ToList();

MyRepository.All.Where(r=>MyCollection.Select(a=>a.id).Contains(r.id))

Linq has an .Intersect that should get you want you need.
Something like this:
var result = MyRepository.Intersect(MyCollection).ToList();
More info:
http://msdn.microsoft.com/en-us/library/system.linq.enumerable.intersect.aspx

Any value in the list - in LINQ

I need to pull all values where the request type is any of the ones I have on the list.
from v in ctx.vEmailSents
where v.RequestType_ID == reqTypeID
group v by v.SentToLab_ID into g
select g.OrderByDescending(x => x.DateSent).FirstOrDefault() into lastV
select new
{
ClaimID = lastV.Claim_ID,
};
reqTypeID is of type List<int>.
How can I use it in Linq to get all records that are in that list?

You can do something like this:
where requestTypes.Contains(v.RequestType_ID)
requestTypes would be the list you talked about.

Splitting Linq List by grouping

for reporting purposes i wanna split a list of purchase orders into multiple lists. One list for each purchase address. I know it's possible to group the list by purchase address, but my question is how to split the list by this purchase address into multiple lists and use these multiple list to create individual reporting files.
code:
(from o in orders
group o by new {field1, field2, field3, field4} into og
orderby og.Key.field1
select new ViewClass
{
purchaseAddress = og.Key.field1,
product = og.key.field2,
count = og.count
}).ToList()
question: how to split above list into multiple lists for each purchaseAddress?

There's a built-in function that I think does what you want. If I assume that your code is assigned to a variable called query then you can write this:
ILookup<string, ViewClass> queryLists = query.ToLookup(x => x.purchaseAddress);
This essentially creates a list of lists that you access like a dictionary, except that each value is a list of zero or more values. Something like:
IEnumerable<ViewClass> someList = queryLists["Some Address"];

Just turn each group into a List.
select new ViewClass
{
purchaseAddress = og.Key.field1,
product = og.key.field2,
count = og.count,
List = og.ToList()
}).ToList();
Oh, your grouping is one way for entities and another way for pages... just regroup.
List<ViewClass> classes = (
from o in orders
group o by new {field1, field2, field3, field4} into og
orderby og.Key.field1
select new ViewClass
{
purchaseAddress = og.Key.field1,
product = og.key.field2,
count = og.count
}).ToList();
List<List<ViewClass>> regrouped = (
from c in classes
group c by c.purchaseAddress into g
select g.ToList()
).ToList();

Another simple built-in function that you can use is the GroupBy function. It does a similar job as the ToLookup but it means that your new list is IQuerable, not like a dictionary and a few other things (see this article for a good breakdown)
var newList = orders.GroupBy(x => x.field1);
This will return a list of lists grouped by the field(s) you specify.