I have the LINQ to SQL query below which works fine, except that I would like to get the "items" selected from "table3" to be put into a single entity object, instead what I'm getting is a new entity with the same Id but different item for each row.
What do I need to do to achieve this?
Thanks!
var result =
from table1 in db.Table1
join table2 in db.Table2 on table1.fkId equals table2.fkId
join table3 in db.Table3 on table2.fkAid equals table3.Id into items
select new Entity
{
Id = table1.Id,
Name = table1.Name,
Items = items.Select(x => new AEntity { Id = x.Id, Name = x.Name }).ToList()
};
return result.ToList();
Edit to elaborate:
From the code above I could get, for example, the following result (pseudocode):
{
Entity
{
Id = 1,
Name = "1",
Items
{
AEntity
{
Name = "33"
Id = 33
}
}
},
Entity
{
Id = 1,
Name = "1",
Items
{
AEntity
{
Id = 44,
Name = "44"
}
}
},
Entity
{
Id = 2,
Name = "2",
Items
{
AEntity
{
Id = 55,
Name = "55"
}
}
}
}
But I want this:
{
Entity
{
Id = 1,
Name = "1",
Items
{
AEntity
{
Id = 33,
Name = "33"
},
AEntity
{
Id = 44,
Name = "44"
}
}
},
Entity
{
Id = 2,
Name = "2",
Items
{
AEntity
{
Id = 55,
Name = "55"
}
}
}
}
I hope that clarifies it a bit.
Once again another person falls victim to "trying to do SQL in Linq". The correct way to do this (in Linq) is...*
var items = context.Entities.Include(x => x.AEntities).ToList();
However if you ARE trying to learn to use an ORM, FOR THE LOVE OF ALL THAT IS HOLY DO NOT USE LINQ2SQL. Its broken, unsupported and out of date.
PLEASE USE Entity Framework.
Now you should google Entity Framework Many to Many or One to Many Associations.
Failing that...
var items = from item1 in db.Table1
select new
{
Id = table1.Id,
Name = table1.Name,
Items = db.Table3
.Where(x => db.Table2
.Where(t2 => t2.fkId == item1.fkId)
.Select(t2 => t2.fkAid)
.Contains(x.Id)).ToList()
};
But that just looks ugly.
*Table 2 looks like the age old pattern of, "Databases can't do Many to Many, so we are going to put in an intermediate table that has no data what-so-ever".
Related
I have the below set of data
Where each City belongs to a specific Department, which belongs to a specific Region, which belongs to a specific Country (in this case there is only one country: France).
This data is contained in a CSV file which I can read from on a row-by-row basis, however my goal is to convert this data into a tree structure (with France being at the root).
Each of these nodes will be given a specific Id value, which is something I've already gone and done, but the tricky part is that each node here must also contain a ParentId (for instance Belley and Gex need the ParentId of Ain, but Moulins and Vichy need the ParentId of Aller).
Below is a snippet of code I've written that has assigned an Id value to each name in this data set, along with some other values:
int id = 0;
List<CoverageAreaLevel> coverageAreas = GetCoverageAreaDataFromCsv(path, true);
List<LevelList> levelLists = new List<LevelList>
{
new LevelList { Names = coverageAreas.Select(a => a.Level1).Distinct().ToList(), Level = "1" },
new LevelList { Names = coverageAreas.Select(a => a.Level2).Distinct().ToList(), Level = "2" },
new LevelList { Names = coverageAreas.Select(a => a.Level3).Distinct().ToList(), Level = "3" },
new LevelList { Names = coverageAreas.Select(a => a.Level4).Distinct().ToList(), Level = "4" }
};
List<CoverageArea> newCoverageAreas = new List<CoverageArea>();
foreach (LevelList levelList in levelLists)
{
foreach (string name in levelList.Names)
{
CoverageArea coverageArea = new CoverageArea
{
Id = id++.ToString(),
Description = name,
FullDescription = name,
Level = levelList.Level
};
newCoverageAreas.Add(coverageArea);
}
}
The levelLists variable contains a sort-of heirarchical structure of the data that I'm looking for, but none of the items in that list are linked together by anything.
Any idea of how this could be implemented? I can manually figure out each ParentId, but I'd like to automate this process, especially if this needs to be done in the future.
The solution from #Camilo is really good and pragmatic. I would also suggest the use of a tree.
A sample implementation:
var countries = models.GroupBy(xco => xco.Country)
.Select((xco, index) =>
{
var country = new Tree<String>();
country.Value = xco.Key;
country.Children = xco.GroupBy(xr => xr.Region)
.Select((xr, xrIndex) =>
{
var region = new Tree<String>();
region.Value = xr.Key;
region.Parent = country;
region.Children =
xr.GroupBy(xd => xd.Department)
.Select((xd, index) =>
{
var department = new Tree<String>();
department.Value = xd.Key;
department.Parent = region;
department.Children = xd
.Select(xc => new Tree<String> { Value = xc.City, Parent = department });
return department;
});
return region;
});
return country;
});
public class Tree<T>
{
public IEnumerable<Tree<T>> Children;
public T Value;
public Tree<T> Parent;
}
One way you could solve this is by building dictionaries with the names and IDs of each level.
Assuming you have data like this:
var models = new List<Model>
{
new Model { Country = "France", Region = "FranceRegionA", Department = "FranceDept1", City = "FranceA" },
new Model { Country = "France", Region = "FranceRegionA", Department = "FranceDept1", City = "FranceB" },
new Model { Country = "France", Region = "FranceRegionA", Department = "FranceDept2", City = "FranceC" },
new Model { Country = "France", Region = "FranceRegionB", Department = "FranceDept3", City = "FranceD" },
new Model { Country = "Italy", Region = "ItalyRegionA", Department = "ItalyDept1", City = "ItalyA" },
new Model { Country = "Italy", Region = "ItalyRegionA", Department = "ItalyDept2", City = "ItalyB" },
};
You could do something like this, which can probably be improved further if needed:
var countries = models.GroupBy(x => x.Country)
.Select((x, index) => Tuple.Create(x.Key, new { Id = index + 1 }))
.ToDictionary(x => x.Item1, x => x.Item2);
var regions = models.GroupBy(x => x.Region)
.Select((x, index) => Tuple.Create(x.Key, new { ParentId = countries[x.First().Country].Id, Id = index + 1 }))
.ToDictionary(x => x.Item1, x => x.Item2);
var departments = models.GroupBy(x => x.Department)
.Select((x, index) => Tuple.Create(x.Key, new { ParentId = regions[x.First().Region].Id, Id = index + 1 }))
.ToDictionary(x => x.Item1, x => x.Item2);
var cities = models
.Select((x, index) => Tuple.Create(x.City, new { ParentId = departments[x.Department].Id, Id = index + 1 }))
.ToDictionary(x => x.Item1, x => x.Item2);
The main idea is to leverage the index parameter of the Select method and the speed of dictionaries to find the parent ID.
Sample output from a fiddle:
countries:
[France, { Id = 1 }],
[Italy, { Id = 2 }]
regions:
[FranceRegionA, { ParentId = 1, Id = 1 }],
[FranceRegionB, { ParentId = 1, Id = 2 }],
[ItalyRegionA, { ParentId = 2, Id = 3 }]
departments:
[FranceDept1, { ParentId = 1, Id = 1 }],
[FranceDept2, { ParentId = 1, Id = 2 }],
[FranceDept3, { ParentId = 2, Id = 3 }],
[ItalyDept1, { ParentId = 3, Id = 4 }],
[ItalyDept2, { ParentId = 3, Id = 5 }]
cities:
[FranceA, { ParentId = 1, Id = 1 }],
[FranceB, { ParentId = 1, Id = 2 }],
[FranceC, { ParentId = 2, Id = 3 }],
[FranceD, { ParentId = 3, Id = 4 }],
[ItalyA, { ParentId = 4, Id = 5 }],
[ItalyB, { ParentId = 5, Id = 6 }]
First question :)
I have a List<Materiau> (where Materiau implements IComparable<Materiau>), and I would like to remove all duplicates and add them together
(if two Materiau is the same (using the comparator), merge it to the first and remove the second from the list)
A Materiau contains an ID and a quantity, when I merge two Materiau using += or +, it keeps the same ID, and the quantity is added
I cannot control the input of the list.
I would like something like this:
List<Materiau> materiaux = getList().mergeDuplicates();
Thank you for your time :)
Check out Linq! Specifically the GroupBy method.
I don't know how familiar you are with sql, but Linq lets you query collections similarly to how sql works.
It's a bit in depth to explain of you are totally unfamiliar, but Code Project has a wonderful example
To sum it up:
Imagine we have this
List<Product> prodList = new List<Product>
{
new Product
{
ID = 1,
Quantity = 1
},
new Product
{
ID = 2,
Quantity = 2
},
new Product
{
ID = 3,
Quantity = 7
},
new Product
{
ID = 4,
Quantity = 3
}
};
and we wanted to group all the duplicate products, and sum their quantities.
We can do this:
var groupedProducts = prodList.GroupBy(item => item.ID)
and then select the values out of the grouping, with the aggregates as needed
var results = groupedProducts.Select( i => new Product
{
ID = i.Key, // this is what we Grouped By above
Quantity = i.Sum(prod => prod.Quantity) // we want to sum up all the quantities in this grouping
});
and boom! we have a list of aggregated products
Lets say you have a class
class Foo
{
public int Id { get; set; }
public int Value { get; set; }
}
and a bunch of them inside a list
var foocollection = new List<Foo> {
new Foo { Id = 1, Value = 1, },
new Foo { Id = 2, Value = 1, },
new Foo { Id = 2, Value = 1, },
};
then you can group them and build the aggregate on each group
var foogrouped = foocollection
.GroupBy( f => f.Id )
.Select( g => new Foo { Id = g.Key, Value = g.Aggregate( 0, ( a, f ) => a + f.Value ) } )
.ToList();
List<Materiau> distinctList = getList().Distinct(EqualityComparer<Materiau>.Default).ToList();
I have the following list of TestParam... This is just a parameter list that is doing to determine how a query is going to be run. In the following case, the expected result would be to be executed against all the combinations of different parameters. Hence, a list of lists, with CustomerId 33 together with each product Id available in the list...
List<TestParam> testList = new List<TestParam>();
testList.Add(new TestParam() { Name = "CustomerId", Value = "33" });
testList.Add(new TestParam() { Name = "ProductId", Value = "1" });
testList.Add(new TestParam() { Name = "ProductId", Value = "2" });
testList.Add(new TestParam() { Name = "ProductId", Value = "3" });
testList.Add(new TestParam() { Name = "ProductId", Value = "4" });
testList.Add(new TestParam() { Name = "ProductId", Value = "5" });
testList.Add(new TestParam() { Name = "ProductId", Value = "6" });
testList.Add(new TestParam() { Name = "ProductId", Value = "7" });
testList.Add(new TestParam() { Name = "ProductId", Value = "8" });
TestParam is a normal encapsulated parameter class having a name and a value...
public class TestParam
{
public string Name { get; set; }
public string Value { get; set; }
}
The end result would be a list of lists, having CustomerId 33, with all the rest of the products. The same result would be acquired if I had different names and values in the list of TestParam (the above is just an example).
The following code, ends up with several lists depending on the combinations of the list above...
// First get a list of distinct unique param collections...
List<string> distinctParameterNames = new List<string>();
testList.GroupBy(x => x.Name).ForEach(paramName => {
distinctParameterNames.Add(paramName.Key);
});
// Get counts
List<int> combinationList = new List<int>();
foreach (var x in distinctParameterNames) {
combinationList.Add(testList.Where(y=>y.Name == x).Count());
}
// Will contain 2 lists, one having all combinations of parameters named CustomerId, and another with ProductId combinations...
List<List<TestParam>> parameterList = new List<List<TestParam>>();
foreach (var x in distinctParameterNames) {
// Loop
List<TestParam> parameter = new List<TestParam>();
testList.Where(paramName => paramName.Name == x).ForEach(y =>
{
parameter.Add(new TestParam() { Name = y.Name, Value = y.Value });
});
parameterList.Add(parameter);
}
It would be an intersect between the list, and the end result will be a list of lists, and each list will have the combinations below... So a run would return (in this case) :
Customer 33, Product Id 1
Customer 33, Product Id 2
Customer 33, Product Id 3
Customer 33, Product Id 4
Customer 33, Product Id 5
Customer 33, Product Id 6
Customer 33, Product Id 7
Customer 33, Product Id 8
What would be the most efficient and generic way to do this?
The following is the solution that I was looking for...
public static List<List<T>> AllCombinationsOf<T>(params List<T>[] sets)
{
// need array bounds checking etc for production
var combinations = new List<List<T>>();
// prime the data
foreach (var value in sets[0])
combinations.Add(new List<T> { value });
foreach (var set in sets.Skip(1))
combinations = AddExtraSet(combinations, set);
return combinations;
}
private static List<List<T>> AddExtraSet<T>
(List<List<T>> combinations, List<T> set)
{
var newCombinations = from value in set
from combination in combinations
select new List<T>(combination) { value };
return newCombinations.ToList();
}
Usage (continues with my code snippet of the question itself) :
var intersection = AllCombinationsOf(parameterList.ToArray());
get all the list of customer first like this
var customers = from a in testlist where a.name='customerid'
select a;
var products = from a in testlist where a.name='productid'
select a;
then loop customers
for(var c in customers)
{
loop products
for(var p in products)
{
var customerproducts = new CustomerProducts{
Customer = c.Name +' ' + c.Value
Product = p.Name + ' ' + p.value
};
then add it into a list
}
}
The list needs to be grouped by Name, then it can be joined several times depending on count of groups:
var groups = testList.GroupBy(_ => _.Name);
IEnumerable<IEnumerable<TestParam>> result = null;
foreach (var g in groups)
{
var current = g.Select(_ => new[] { _ });
if (result == null)
{
result = current;
continue;
}
result = result.Join(current, _ => true, _ => true, (actual, c) => actual.Concat(c));
}
// check result
foreach (var i in result)
{
Console.WriteLine(string.Join(", ", i.Select(_ => string.Format("{0}-{1}", _.Name, _.Value))));
}
I have 50,000 documents in my raven database, but when I I run this query the Id of the latestProfile object is returned as 9999 (the first id in the db is 0, so this is the ten thousandth item).
//find the profile with the highest ID now existing in the collection
var latestProfile = session.Query<SiteProfile>()
.Customize(c => c.WaitForNonStaleResults())
.OrderByDescending(p => p.Id)
.FirstOrDefault();
//lastProfile.Id is 9999 here
//See how many items there are in the collection. This returns 50,000
var count = session.Query<SiteProfile>()
.Customize(c => c.WaitForNonStaleResults()).Count();
My guess is that Raven is paging before my OrderByDescending statement, but
The default page size is 10, and even the max is 1024
All the Parts of this are either IRavenQueryable or IQueryable
It is also not a stale index as I have tested this with WaitForNonStaleResults()
My expected result here is the most recent id I added (50,000) to be the item returned here, but yet it is not.
Why not? This looks like a bug in Raven to me.
EDIT:
Ok, so I now know exactly why, but it still looks like a bug. Here is a list of the items from that same list actualised by a ToArray()
{ Id = 9999 },
{ Id = 9998 },
{ Id = 9997 },
{ Id = 9996 },
{ Id = 9995 },
{ Id = 9994 },
{ Id = 9993 },
{ Id = 9992 },
{ Id = 9991 },
{ Id = 9990 },
{ Id = 999 }, //<-- Whoops! This is text order not int order
{ Id = 9989 },
So even though my Id column is an integer because Raven stores it internally as a string it is ordering by that representation. Clearly Ravens Queryable implementation is resolving the ordering before checking types
I have read that you can define sort order to use integer sorting on defined indexes but really, this should not matter. In a strongly typed language integers should be sorted as integers.
Is there a way to make this Id ordering correct? Do I have actually have to resort to creating a special index on the id column just to get integers ordered correctly?
UPDATE 2:
I am now using an index as follows:
public SiteProfiles_ByProfileId()
{
Map = profiles => from profile in profiles
select new
{
profile.Id
};
Sort(x => x.Id, SortOptions.Int);
}
To try and force it to understand integers. I can see that my index is called via the Raven server console as follows:
Request # 249: GET - 3 ms - Bede.Profiles - 200 - /indexes/SiteProfiles/ByProfileId?&pageSize=1&sort=-__document_id&operationHeadersHash=-1789353429
Query:
Time: 3 ms
Index: SiteProfiles/ByProfileId
Results: 1 returned out of 20,000 total.
but still it comes back with string ordered results. I have seen advice not to use integers as the id, but that would cause massive issues on this project as there are 3rd parties referencing the current ids (in the old service this is designed to replace).
UPDATE 3: I have specific unit test that shows the issue. it appears to work fine for any integer property except for the Id.
[TestMethod]
public void Test_IndexAllowsCorrectIntSortingWhenNotId()
{
using (var store = new EmbeddableDocumentStore() {RunInMemory = true})
{
store.Initialize();
IndexCreation.CreateIndexes(typeof(MyFakeProfiles_ByProfileId).Assembly, store);
using (var session = store.OpenSession())
{
var profiles = new List<MyFakeProfile>()
{
new MyFakeProfile() { Id=80, Age = 80, FirstName = "Grandpa", LastName = "Joe"},
new MyFakeProfile() { Id=9, Age = 9,FirstName = "Jonny", LastName = "Boy"},
new MyFakeProfile() { Id=22, Age = 22, FirstName = "John", LastName = "Smith"}
};
foreach (var myFakeProfile in profiles)
{
session.Store(myFakeProfile, "MyFakeProfiles/" + myFakeProfile.Id);
}
session.SaveChanges();
var oldestPerson = session.Query<MyFakeProfile>().Customize(c => c.WaitForNonStaleResults())
.OrderByDescending(p => p.Age).FirstOrDefault();
var youngestPerson = session.Query<MyFakeProfile>().Customize(c => c.WaitForNonStaleResults())
.OrderBy(p => p.Age).FirstOrDefault();
var highestId = session.Query<MyFakeProfile>("MyFakeProfiles/ByProfileId").Customize(c => c.WaitForNonStaleResults())
.OrderByDescending(p => p.Id).FirstOrDefault();
var lowestId = session.Query<MyFakeProfile>("MyFakeProfiles/ByProfileId").Customize(c => c.WaitForNonStaleResults())
.OrderBy(p => p.Id).FirstOrDefault();
//sanity checks for ordering in Raven
Assert.AreEqual(80,oldestPerson.Age); //succeeds
Assert.AreEqual(9, youngestPerson.Age);//succeeds
Assert.AreEqual(80, highestId.Id);//fails
Assert.AreEqual(9, lowestId.Id);//fails
}
}
}
private void PopulateTestValues(IDocumentSession session)
{
var profiles = new List<MyFakeProfile>()
{
new MyFakeProfile() { Id=80, Age = 80, FirstName = "Grandpa", LastName = "Joe"},
new MyFakeProfile() { Id=9, Age = 9,FirstName = "Jonny", LastName = "Boy"},
new MyFakeProfile() { Id=22, Age = 22, FirstName = "John", LastName = "Smith"}
};
foreach (var myFakeProfile in profiles)
{
session.Store(myFakeProfile, "MyFakeProfiles/" + myFakeProfile.Id);
}
}
}
public class MyFakeProfile
{
public int Id { get; set; }
public int Age { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
}
public class MyFakeProfiles_ByProfileId : AbstractIndexCreationTask<MyFakeProfile>
{
// The index name generated by this is going to be SiteProfiles/ByProfileId
public MyFakeProfiles_ByProfileId()
{
Map = profiles => from profile in profiles
select new
{
profile.Id
};
Sort(x => (int)x.Id, SortOptions.Int);
}
}
You need to specify the type of the field on the index, see http://ravendb.net/docs/2.5/client-api/querying/static-indexes/customizing-results-order
Side note, IDs in RavenDB are always strings. You seem to be trying to use integer IDs - don't do that.
You can provide multiple Sort field, as you have only defined it for Id:
public SiteProfiles_ByProfileId()
{
Map = profiles => from profile in profiles
select new
{
profile.Id
};
Sort(x => x.Id, SortOptions.Int);
Sort(x => x.Age, SortOptions.Int);
}
BUT ... I am unsure of the effects of applying a sort on a field that isn't mapped.
You may have to extend the mapping to select both fields, like this:
public SiteProfiles_ByProfileId()
{
Map = profiles => from profile in profiles
select new
{
profile.Id,
profile.Age
};
Sort(x => x.Id, SortOptions.Int);
Sort(x => x.Age, SortOptions.Int);
}
var pairs = new [] { new { id = 1, name = "ram", dept = "IT", sal = "3000" }, new { id = 2, name = "ramesh", dept = "IT", sal = "5000" }, new { id = 3, name = "rahesh", dept = "NONIT", sal = "2000" },
new { id = 5, name = "rash", dept = "NONIT", sal = "7000" } };
var query = from stud in pairs
where (stud.name.StartsWith("r") && stud.id % 2 != 0)
//orderby stud.sal descending
group stud by stud.dept into grps
select new { Values = grps, Key = grps.Key, maxsal=grps.Max() };
////select new { id = stud.id };
foreach (dynamic result in query)
{
Console.WriteLine(result.Key);
Console.WriteLine(result.maxsal);
foreach (dynamic result2 in result.Values)
{
Console.WriteLine(result2.id + "," + result2.sal);
}
}
Console.Read();
I am getting the error "At least one object must implement IComparable.", can someone explain me why iam I getting this error ?
You are calling grps.Max() to get maximnum item in group. Your anonymous objects are not comparable. How Linq will know which one is maximum from them? Should it use id property for comparison, or name?
I believe you want to select max salary:
maxsal = grps.Max(s => Int32.Parse(s.sal))