I have a database with a specific id with recorded Time's, I need help on trying to figure out time gap's between an ID's time's e.g 13:05:15 and 13:05:45 though if the time gap is over 10/15 seconds it needs to be recorded so it can be used in say a text file/other data etc. I previously asked a similar question on here, here is what my code looks like so far:
This class is used to manipulate data through the linq var being queried/looped
public class Result
{
public bool LongerThan10Seconds { get; set; }
public int Id { get; set; }
public DateTime CompletionTime { get; set; }
}
This is the foor loop within a separate class which was my original idea
using (var data = new ProjectEntities())
{
Result lastResult = null;
List<Result> dataResults = new List<Result>();
foreach(var subResult in data.Status.Select(x => x.ID).Distinct().Select(Id => data.Status.Where(x => x.ID == Id).OrderBy(x => x.Time)))
{
if (lastResult != null)
{
if (subResult.CompletionTime.Subtract(lastResult.CompletionTime).Seconds > 10)
dataResults.Add(subResult);
}
lastResult = subResult;
}
Which I got the error:
Linq.IOrderedQueryAble does not contain a definition for 'CompletionTime' and no Extension method 'CompletionTime' accepting a first argument of type 'System.Linq.IOrderedQueryable.
I changed the for loop to use an object of the manipulation class
foreach(Result subResult in data.AssetStatusHistories.Select(x => x.ID).Distinct().SelectMany(Id => data.AssetStatusHistories.Where(x => x.ID == Id).OrderBy(x => x.TimeStamp)))
{
if (lastResult != null)
{
if (subResult.CompletionTime.Subtract(lastResult.CompletionTime).Seconds > 10)
{
vehicleResults.Add(subResult);
}
}
lastResult = subResult;
}
Though now I get the error: Cannot convert type 'Project.Status' to 'Project.Result'
Does anyone possibly have a solution to get around this I have looked through a few resources but haven't been able to find anything of helps also even on Microsoft's Linq Forum. Any help is much appreciated ! :)
Try adding .ToList() to the end of your LINQ statement, after OrderBy:
var results = data.Status.Select(x => x.ID).Distinct()
.Select(Id => data.Status.Where(x => x.ID == Id)
.OrderBy(x => x.Time)
.ToList();
foreach(var subResult in results))
{
...
}
Also, I think you could modify your LINQ to do a GroupBy of the ID column, but that's something you could do research on if you wish. (Tutorial)
Your linq query (in the second try) will return an IEnumerable of whatever is the element type of data.AssetStatusHistories. I assume this is some kind of IEnumerable<Project.Status>, so you're in fact trying to assign Project.Status objects to an iterator variable (subResult) of type Result, which is why you're getting the error Cannot convert type 'Project.Status' to 'Project.Result'.
So your problem is not really in the linq query, you just need a way to convert your Project.Status objects to Project.Result objects.
Related
I have a table named dbo.EmployeeType with three records:
PK_EmployeetypeID EmployeeTypeName
1 Project Manager
2 Business Analyst
3 Developer
I have this piece of Linq code:
public static string GetTypeByID(int id)
{
using (ProjectTrackingEntities1 db = new ProjectTrackingEntities1())
{
var type = db.EmployeeTypes.Select(o => new LOOKUPEmployeeType
{
PK_EmployeeTypeID = id,
EmployeeTypeName = o.EmployeeTypeName
});
return type.FirstOrDefault().EmployeeTypeName;
}
}
No matter what id I send to it, it returns Project Manager, and I'm confused as to why.
You need to apply a filter, otherwise you're just returning the first record and hard coding the ID. Try this:
public static string GetTypeByID(int id)
{
using (ProjectTrackingEntities1 db = new ProjectTrackingEntities1())
{
//Here we apply a filter, the lambda here is what creates the WHERE clause
var type = db.EmployeeTypes
.FirstOrDefault(et => et.PK_EmployeeTypeID == id);
if(type != null)
{
return type.EmployeeTypeName;
}
else
{
return "";
}
}
}
Note that using FirstOrDefault means if there are no matches, or multiple matches, type will be null and you will get an empty string returned.
Set a breakpoint on type = ... and inspect it. You have no Where in there so you get all - and Select just makes LOOKUPEmployeeTypes out of all of them.
FirstOrDefault then returns the first of those 3 which is always the ProjManager
Fix:
var type = db
.EmployeeTypes
.Where( o => o.Id == id)
.Select(o => new LOOKUPEmployeeType
{
PK_EmployeeTypeID = id,
EmployeeTypeName = o.EmployeeTypeName
});
In your code you only return the first value. You need to tell EF which value you need to return.
Let us assume you need the value with Id=2. Instead of Select(), use Single(x => x.Id == 2) or First(x => x.Id == 2).
i found the way to check is the value contains in simple array :
var filter = Builders<Post>.Filter.AnyEq(x => x.Tags, "mongodb");
But how to find a complex item with many fields by a concrete field ?
I found the way to write it via the dot notation approach with BsonDocument builder, but how can i do it with typed lambda notations ?
upd
i think it some kind of
builderInst.AnyIn(p => p.ComplexCollection.Select(ml => ml.Id), mlIds)
but can't check right now, is anyone could help ?
There is ElemMatch
var filter = Builders<Post>.Filter.ElemMatch(x => x.Tags, x => x.Name == "test");
var res = await collection.Find(filter).ToListAsync()
Here's an example that returns a single complex item from an array (using MongoDB.Driver v2.5.0):
Simple Data Model
public class Zoo
{
public List<Animal> Animals { get; set; }
}
public class Animal
{
public string Name { get; set; }
}
Option 1 (Aggregation)
public Animal FindAnimalInZoo(string animalName)
{
var zooWithAnimalFilter = Builders<Zoo>.Filter
.ElemMatch(z => z.Animals, a => a.Name == animalName);
return _db.GetCollection<Zoo>("zoos").Aggregate()
.Match(zooWithAnimalFilter)
.Project<Animal>(
Builders<Zoo>.Projection.Expression<Animal>(z =>
z.Animals.FirstOrDefault(a => a.Name == animalName)))
.FirstOrDefault(); // or .ToList() to return multiple
}
Option 2 (Filter & Linq) This was about 5x slower for me
public Animal FindAnimalInZoo(string animalName)
{
// Same as above
var zooWithAnimalFilter = Builders<Zoo>.Filter
.ElemMatch(z => z.Animals, a => a.Name == animalName);
var zooWithAnimal = _db.GetCollection<Zoo>("zoos")
.Find(zooWithAnimalFilter)
.FirstOrDefault();
return zooWithAnimal.Animals.FirstOrDefault(a => a.Name == animalName);
}
You need the $elemMatch operator. You could use Builders<T>.Filter.ElemMatch or an Any expression:
Find(x => x.Tags.Any(t => t.Name == "test")).ToListAsync()
http://mongodb.github.io/mongo-csharp-driver/2.0/reference/driver/expressions/#elemmatch
As of the 2.4.2 release of the C# drivers, the IFindFluent interface can be used for querying on array element. ElemMatch cannot be used on an array of strings directly, whereas the find interface will work on either simple or complex types (e.g. 'Tags.Name') and is strongly typed.
FilterDefinitionBuilder<Post> tcBuilder = Builders<Post>.Filter;
FilterDefinition<Post> tcFilter = tcBuilder.Eq("Tags","mongodb") & tcBuilder.Eq("Tags","asp.net");
...
await myCollection.FindAsync(tcFilter);
Linq driver uses the aggregation framework, but for a query with no aggregation operators a find is faster.
Note that this has been broken in previous versions of the driver so the answer was not available at the time of original posting.
I have the following classes:
public class Company
{
[BsonId]
public string dealerId = null;
public List<Dealer> dealers = new List<Dealer>();
}
public class Dealer
{
public string dId = null;
public int dIndex = -1;
public List<AutoStore> stores = new List<AutoStore>();
}
public class AutoStore
{
public string type = null;
public Dictionary<string, object> data = new Dictionary<string, object>();
}
I am able to store the Company class objects in Mongo with Insert(). The problem is when I search for a document and try to use LINQ on the List<> items. I constantly get an exception .
var query = collection.AsQueryable<Company>()
.Where(cpy =>
cpy.dealers.Where(dlr =>
dlr.stores.Count == 1).Count() > 0) ;
Running this code I get:
System.NotSupportedException: Unable to determine the serialization
information for the expression: Enumerable.Count
I just started using Mongo today, but I thought the LINQ support was more mature. Can anyone tell me if I can do a nested array query like I've done with C# andLINQ ?
As soon as I remove the Where() on any of the List<> , that exception isn't thrown
Going by your exception the problem area is within where you are doing Where statements.
As I said in my comment. Try to do:
var v = collection.AsQueryable<Company>().Where(cpy => cpy.Dealers.Any(dlr => dlr.Stores.Count == 1));
You are currently doing something like:
var dealers = collection.AsQueryable<Company>().Select(cpy => cpy.Dealers);
var dealersWithStores = dealers.Where(dealer => dealer.Stores.Count == 1);
You are then checking if there are any dealers with stores by calling count and checking if that is more than 0 to get your bool in the where. All of this is the same as calling IEnumerable.Any(). See if this works? :)
You could write you query more efficiently as
var query = collection.AsQueryable<Company>()
.Where(c => c.dealers.Any(d => d.stores.Count == 1);
If the Mongo querty provider is struggling to support IList, you might find
var query = collection.AsQueryable<Company>()
.Where(c => c.dealers.Any(d => d.stores.Count() == 1);
works better. If so, reports of the maturity of MongoDBs query provider are exaggerated.
I am working with an NHibernate project that has a method that returns an IQuery object.
I want to find the oldest car with a particular colour.
At the moment it returns the oldest car only if you if you specify the colour correctly (or don't specify it at all).
I can see roughly what I am doing wrong (I am getting the maxAge for the whole table and then adding it as a restriction on the existing IQueryOver).
How do I change the code to get the max age just for existing IQueryOver?
private IQueryOver GetFilteredQuery()
{
var query = Session.QueryOver<Car>();
if (this.Colour != nulI)
{
query.Where(x => x.Colour == this.Colour));
}
if (this.GetOldestCar == true)
{
QueryOver<Car> maxAge= QueryOver.Of<Car>()
.SelectList(c => c.SelectMax(x => x.Age));
query.Where(Subqueries.WhereProperty<Car>(i => i.Age).Eq(maxAge));
}
return query;
}
To get the oldest Car, you may try :
var query = Session.QueryOver<Car>().OrderBy(x=>x.Age).Desc().Take(1);
This would lead to :
private IQueryOver GetFilteredQuery()
{
var query = Session.QueryOver<Car>();
if (this.Colour != null)
{
query.Where(x => x.Colour == this.Colour));
}
if (this.GetOldestCar)
{
query.OrderBy(x=>x.Age).Desc().Take(1)
}
return query;
}
The following LINQ statement:
public override List<Item> SearchListWithSearchPhrase(string searchPhrase)
{
List<string> searchTerms = StringHelpers.GetSearchTerms(searchPhrase);
using (var db = Datasource.GetContext())
{
return (from t in db.Tasks
where searchTerms.All(term =>
t.Title.ToUpper().Contains(term.ToUpper()) &&
t.Description.ToUpper().Contains(term.ToUpper()))
select t).Cast<Item>().ToList();
}
}
gives me this error:
System.NotSupportedException: Local
sequence cannot be used in LINQ to SQL
implementation of query operators
except the Contains() operator.
Looking around it seems my only option is to get all my items first into a generic List, then do a LINQ query on that.
Or is there a clever way to rephrase the above LINQ-to-SQL statement to avoid the error?
ANSWER:
Thanks Randy, your idea helped me to build the following solution. It is not elegant but it solves the problem and since this will be code generated, I can handle up to e.g. 20 search terms without any extra work:
public override List<Item> SearchListWithSearchPhrase(string searchPhrase)
{
List<string> searchTerms = StringHelpers.GetSearchTerms(searchPhrase);
using (var db = Datasource.GetContext())
{
switch (searchTerms.Count())
{
case 1:
return (db.Tasks
.Where(t =>
t.Title.Contains(searchTerms[0])
|| t.Description.Contains(searchTerms[0])
)
.Select(t => t)).Cast<Item>().ToList();
case 2:
return (db.Tasks
.Where(t =>
(t.Title.Contains(searchTerms[0])
|| t.Description.Contains(searchTerms[0]))
&&
(t.Title.Contains(searchTerms[1])
|| t.Description.Contains(searchTerms[1]))
)
.Select(t => t)).Cast<Item>().ToList();
case 3:
return (db.Tasks
.Where(t =>
(t.Title.Contains(searchTerms[0])
|| t.Description.Contains(searchTerms[0]))
&&
(t.Title.Contains(searchTerms[1])
|| t.Description.Contains(searchTerms[1]))
&&
(t.Title.Contains(searchTerms[2])
|| t.Description.Contains(searchTerms[2]))
)
.Select(t => t)).Cast<Item>().ToList();
default:
return null;
}
}
}
Ed, I've run into a similiar situation. The code is below. The important line of code is where I set the memberList variable. See if this fits your situation. Sorry if the formatting didn't come out to well.
Randy
// Get all the members that have an ActiveDirectorySecurityId matching one in the list.
IEnumerable<Member> members = database.Members
.Where(member => activeDirectoryIds.Contains(member.ActiveDirectorySecurityId))
.Select(member => member);
// This is necessary to avoid getting a "Queries with local collections are not supported"
//error in the next query.
memberList = members.ToList<Member>();
// Now get all the roles associated with the members retrieved in the first step.
IEnumerable<Role> roles = from i in database.MemberRoles
where memberList.Contains(i.Member)
select i.Role;
Since you cannot join local sequence with linq table, the only way to translate the above query into SQL woluld be to create WHERE clause with as many LIKE conditions as there are elements in searchTerms list (concatenated with AND operators). Apparently linq doesn't do that automatically and throws an expception instead.
But it can be done manually by iterating through the sequence:
public override List<Item> SearchListWithSearchPhrase(string searchPhrase)
{
List<string> searchTerms = StringHelpers.GetSearchTerms(searchPhrase);
using (var db = Datasource.GetContext())
{
IQueryable<Task> taskQuery = db.Tasks.AsQueryable();
foreach(var term in searchTerms)
{
taskQuery = taskQuery.Where(t=>t.Title.ToUpper().Contains(term.ToUpper()) && t.Description.ToUpper().Contains(term.ToUpper()))
}
return taskQuery.ToList();
}
}
Mind that the query is still executed by DBMS as a SQL statement. The only drawback is that searchTerms list shouldn't be to long - otherwise the produced SQL statement won'tbe efficient.