About the homework:
There are casters(witch(0)/fairy(1)) and they have spellpower(int). I stored them in a list.
I'm to find the best of both types. (There can be multiple casters with the same spellpower)
I've come up with this code, but there is a problem. If the caster with the most spellpower is a 1, then the first FindAll won't return anything, because it tries to find the caster with type 0 AND with the most spellpower. How can I get a list containing type 0 caster(s) with the most spellpower, if the caster with the most overall spellpower is type 1?
private List<Caster> BestCasters()
{
List<Caster> temp = new List<Caster>();
temp = casters.FindAll(x => x.SpellPower == casters.Max(y => y.SpellPower) && (x.TypeOfCaster == 0));
temp.AddRange(casters.FindAll(x => x.SpellPower == casters.Max(y => y.SpellPower) && (x.TypeOfCaster == 1)));
temp.OrderBy(x => x.TypeOfCaster).ThenBy(y => y.CasterName);
return temp;
}
The LINQ GroupBy behavior is perfect for this:
var strongest_casters = casters.GroupBy(c => c.TypeOfCaster)
.Select(grp => grp.OrderByDescending(x => x.SpellPower)
.First()
);
Or to return more than one of each type:
var strongest_casters = casters.GroupBy(c => c.TypeOfCaster)
.SelectMany(grp => grp.Where(y.SpellPower == grp.Max(x => x.SpellPower))
);
private List<Caster> BestCasters()
{
var witches = casters.Where(x => x.TypeOfCaster == 0).ToList();
var fairies = casters.Where(x => x.TypeOfCaster == 1).ToList();
int witchesMax = witches.Max(x => x.SpellPower);
int fairiesMax = fairies.Max(x => x.SpellPower);
var temp = witches.Where(x => x.SpellPower == witchesMax).ToList();
temp.AddRange(fairies.Where(x => x.SpellPower == fairiesMax));
return temp.OrderBy(x => x.TypeOfCaster).ThenBy(y => y.CasterName).ToList();
}
If you have to use FindAll like this you should invoke the Max on a subset only containing the casters of the right kind. Of course it would make more sense to split the initial list first and then fetch the strongest caster of each kind.
Since you did not tell what exactly you have to do I can only hope that you are allowed to split :-)
Related
For a schoolproject i have to make a simple website where i have to search members based on what the user types and then display these members. I have 5 properties to look for (first and lastname, sex, level, club). They have to work together but some might be null.
public List<Lid> ZoekLeden(string deelVoornaam, string deelNaam, string geslacht, string niveau, string deelClubNaam)
{
var filteredleden = context.Leden.Include(lid => lid.ClubNrNavigation)
.OrderBy(l => l.Naam)
.Where(l => l.Voornaam.Contains(deelVoornaam))
.Where(l => l.Naam.Contains(deelNaam))
.Where(l => l.Geslacht.Equals(geslacht))
.Where(l => l.Niveau.Equals(niveau))
.Where(l => l.ClubNrNavigation.Naam.Contains(deelClubNaam))
.ToList();
return filteredleden;
}
Sadly it keep returning 0 and i dont know why.
I tested each individual property and they all return the proper members. But the moment i use multiple they always return 0. Does anyone know why this happends and how i can fix it?
Try this
public List<Lid> ZoekLeden(string deelVoornaam, string deelNaam, string geslacht, string niveau, string deelClubNaam)
{
IQueryable<Lid> filteredleden = context.Leden
.Include(lid => lid.ClubNrNavigation);
if (!string.IsNullOrEmpty(deelVoornaam))
filteredleden = filteredleden.Where(l => l.Voornaam.Contains(deelVoornaam));
if (!string.IsNullOrEmpty(deelNaam))
filteredleden = filteredleden.Where(l => l.Naam.Contains(deelNaam))
if (!string.IsNullOrEmpty(geslacht))
filteredleden = filteredleden.Where(l => l.Geslacht.Equals(geslacht))
if (!string.IsNullOrEmpty(niveau))
filteredleden = filteredleden.Where(l => l.Niveau.Equals(niveau))
if (!string.IsNullOrEmpty(deelClubNaam))
filteredleden = filteredleden.Where(l => l.ClubNrNavigation.Naam.Contains(deelClubNaam));
return filteredleden.OrderBy(l => l.Naam).ToList();
}
You're chaining .Where() which is the equivalent of if(bool && bool && bool). Instead, I think you need if(bool || bool || bool)
So the LINQ statement should be:
var filteredleden = context.Leden.Include(lid => lid.ClubNrNavigation)
.OrderBy(l => l.Naam)
.Where(l => l.Voornaam.Contains(deelVoornaam)
|| l.Naam.Contains(deelNaam)
|| l => l.Geslacht.Equals(geslacht)
|| l => l.Niveau.Equals(niveau)
|| l => l.ClubNrNavigation.Naam.Contains(deelClubNaam)
)
.ToList();
If you really do need the &&'s, then theres probably nothing in your dataset that meets all the criteria in the chained .Where()s
I have used this to pick just a single column from the collection but it doesn't and throws casting error.
ClientsDAL ClientsDAL = new DAL.ClientsDAL();
var clientsCollection= ClientsDAL.GetClientsCollection();
var projectNum = clientsCollection.Where(p => p.ID == edit.Clients_ID).Select(p => p.ProjectNo).ToString();
Method:
public IEnumerable<Clients> GetClientsCollection(string name = "")
{
IEnumerable<Clients> ClientsCollection;
var query = uow.ClientsRepository.GetQueryable().AsQueryable();
if (!string.IsNullOrEmpty(name))
{
query = query.Where(x => x.Name.Contains(name));
}
ClientsCollection = (IEnumerable<Clients>)query;
return ClientsCollection;
}
As DevilSuichiro said in comments you should not cast to IEnumerable<T> just call .AsEnumerable() it will keep laziness.
But in your case it looks like you do not need that at all because First or FirstOrDefault work with IQueryable too.
To get a single field use this code
clientsCollection
.Where(p => p.ID == edit.Clients_ID)
.Select(p => p.ProjectNo)
.First() // if you sure that at least one item exists
Or (more safe)
var projectNum = clientsCollection
.Where(p => p.ID == edit.Clients_ID)
.Select(p => (int?)p.ProjectNo)
.FirstOrDefault();
if (projectNum != null)
{
// you find that number
}
else
{
// there is no item with such edit.Clients_ID
}
Or even simpler with null propagation
var projectNum = clientsCollection
.FirstOrDefault(p => p.ID == edit.Clients_ID)?.ProjectNo;
I'm doing a query over two different tables.
In the first query, i get some Ids that I then have to check in another table.
Then I do the first query again with the result of the second query.
This can't be the best way to do this.
But I haven't found a good way to solve it. So some help would be appreciated.
IntOrderInvoiceCostOut y = null;
var list = session.QueryOver<IntOrderInvoiceCostOut>(() => y)
.Where(x => x.IntegrationHandleDate == null)
.Select(Projections.Distinct(Projections.Property(() => y.Externalid)))
.List<string>();
var nonPreliminaryOrders = session.QueryOver<RefImplOrderEntity>()
.WhereRestrictionOn(x => x.ExternalId).IsIn(list.ToList())
.Where(x => x.StatusTypeId != 95)
.Select(x => x.ExternalId)
.List<string>();
var finalList = session.QueryOver<IntOrderInvoiceCostOut>()
.WhereRestrictionOn(x => x.Externalid).IsIn(nonPreliminaryOrders.ToList())
.Where(x => x.IntegrationHandleDate == null)
.OrderBy(x => x.IntegrationCreateDate)
.Asc
.List();
The code works...but i't really ugly.
you could use detacheCriteria for this. I have omitted couple of conditions and you might have to twick a bit as per your requirement.
for example
IntOrderInvoiceCostOut y = null;
var list = QueryOver.Of<IntOrderInvoiceCostOut>(() => y)
.Where(x => x.IntegrationHandleDate == null)
.Select(Projections.Distinct(Projections.Property(() => y.Externalid)))
.DetachedCriteria;
var nonPreliminaryOrders = QueryOver.Of<RefImplOrderEntity>()
.Where(Subqueries.PropertyIn(nameof(RefImplOrderEntity.ExternalId), list));
.Select(x => x.ExternalId)
.DetachedCriteria
var finalList = session.QueryOver<IntOrderInvoiceCostOut>()
.Where(Subqueries.PropertyIn(nameof(IntOrderInvoiceCostOut.ExternalId), nonPreliminaryOrders));
.List();
I have the following two statements :-
var isadminByuser = tms.SecurityRoles.Where(a => a.Name.ToLower() == "administrator")
.Select(a=>a.SecurityRoleUsers.Where(a2 => a2.UserName.ToLower() == user.ToLower()));
if (isadminByuser.Count() >= 1) { return true;}
&
var adminByGroup = tms.SecurityRoles.Where(a => a.Name == "Administrator")
.SingleOrDefault().Groups
.Select(a2 => a2.TMSUserGroups
.Where(a3 => a3.UserName.ToLower() == user.ToLower()));
bool isadminByGroup = adminByGroup.Count() >= 1;
The first var isadminByuser will always have elements (will always be >=1), even if the where clause a3.UserName.ToLower() == user.ToLower())) is false, while the other var will have a count of zero is the where clause (a3.UserName.ToLower() == user.ToLower())) is false. So why will the first var never have a count of zero?
Thanks
The answer to the question asked is that you are selecting an IQueryable<SecurityRoleUsers> when you select
a.SecurityRoleUsers.Where(a2 => a2.UserName.ToLower() == user.ToLower())
which may or may not have a count of 0, but the containing query will return one of these IQueryables for each SecurityRole that matches Name = "administrator", hence the count will always be 1+ if there is at least one matching SecurityRole
Update:
// first get SecurityRoles
bool isadminByuser = tms.SecurityRoles.Where(a => a.Name.ToLower() == "administrator")
// now you're only interested in the related SecurityRoleUsers
.SelectMany( a => a.SecurityRoleUsers )
// now check if any of the SecurityRoleUsers meet your criteria
.Any( sru => sru.UserName.ToLower() == user.ToLower() );
Could you observe sql query differences from ms-sql-profiler
tms.SecurityRoles.Where(a => a.Name.ToLower() == "administrator")
.Select(a=>a.SecurityRoleUsers.Where(a2 => a2.UserName.ToLower() == user.ToLower()));
***
tms.SecurityRoles.Select(a=>a.SecurityRoleUsers.Where(a2 => a2.UserName.ToLower() == user.ToLower())).Where(a => a.Name.ToLower() == "administrator");
How do I write something like this:
int result = database
.Where(x => x.Name == "Criteria")
.Sum(x => x.Count)) ?? 0;
Where it will return the sum value unless linq does not find anything in which case it will return 0.
EDIT: The field is not null-able.
EDIT 2: I am using Entity Framework.
You were very close with your original query. You only needed to cast your Count variable:
int result = database
.Where(x => x.Name == "Criteria")
.Sum(x => (int?)x.Count) ?? 0;
Doing it this way would be a little more efficient and elegant than wrapping it in a Try/Catch.
I suspect you are using Entity Framework. If you were just using Linq-to-Objects, the solutions everybody else have provided would have worked.
This should work fine (no need for ?? 0):
var result = database
.Where(x => x.Name == "Criteria")
.Sum(x => x.Count))
Unless you want to check if x itself is null or not:
var result = database
.Where(x => x != null)
.Where(x => x.Name == "Criteria")
.Sum(x => x.Count))
You can just write:
int result = database
.Where(x => x.Name == "Criteria")
.Sum(x => x.Count));
The Enumerable.Sum method already returns zero on no results. From the documentation:
returns zero if source contains no elements.
This should work just fine:
var result = database.Where(x => x.Name == "Criteria").Sum(x => x.Count));
If no elements are returned by the Where function then the Sum function will return 0.
All of the Linq functions that return an IEnumerable<T> will return an empty collection instead of null.
Use the Aggregate extension method where 0 is a seed value
int sum = database.Where(x=>x.Name == "Criteria")
.Aggregate(0, (total, next) => total +=next);
I did it in a way that no one is going to like but garrantee to work 100% of the time, behold!
int result = 0;
try{
result = database
.Where(x => x.Name == "Criteria")
.Sum(x => x.Count));
} catch (Exception e){ }