Some pseudo-code of the model I'm working with:
User { int Id, string Username }
Activity { int Id, string Name }
Place { int Id, string Name }
Basically I have a bunch of Users and they belong to certain places (many to many relationship in RDBMS world). What I'd like to do now that I've created all of the nodes already is create the relationship between them. To do that I believe I need to get references to each node and then simply create the relationship between them.
Note: So far no relationships exist. It does look like in some of the examples they have added the User nodes with a relationship that points to the RootNode but I have no idea why. I'm not sure if I need to do that or not.
More pseudo-code:
var userRef = _graphClient...GetUserNodeWhereIdEquals(user.Id);
// or something like _graphClient.OutV<User>("[[id={0}]]", user.Id)
// or even just _graphClient.V<User>(id == user.Id)
var placeRef = _graphClient...GetPlaceNodeWhereIdEquals(place.Id);
_graphClient...CreateRelationshipBetween(userRef, placeRef, "belongs_to");
Unfortunately the documentation starts off pretty great then goes south when you get to relationships.
Update 3/29/12
Here's the code I have so far:
foreach (var a in _activityTasks.GetAll())
{
_graphClient.Create(a, new ActivityBelongsTo(_graphClient.RootNode));
}
foreach (var p in _placeTasks.GetAll().Take(1))
{
var placeNode = _graphClient.Create(p, new PlaceBelongsTo(_graphClient.RootNode));
foreach (var activity in p.Activities)
{
Activity activity1 = activity;
var activityNode = _graphClient.RootNode.In<Activity>(ActivityBelongsTo.TypeKey, a => a.Id == activity1.Id).SingleOrDefault();
_graphClient.CreateRelationship(placeNode, new PlaceHasActivity(activityNode.Reference));
}
}
The activity nodes are created fine. The place node is created fine. An error is now being thrown when trying to get the activityNode. It's a rather large stack trace so I'll try to paraphrase here:
Received an exception when executing the request.
The query was: g.v(p0).in(p1).filter{ it[p2] == p3
}.drop(p4).take(p5)._()
The exception was: Value cannot be null. Parameter name: key
System.ArgumentNullException: Value cannot be null.Parameter name: key
at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue
value, Boolean add) ... The raw response body was: [ {
"outgoing_relationships" :
"http://localhost:7474/db/data/node/2/relationships/out", "data" : {
"Name" : "Aerobics", "Id" : 2 }, "all_typed_relationships" :
"http://localhost:7474/db/data/node/2/relationships/all/{-list|&|types}",
"traverse" :
"http://localhost:7474/db/data/node/2/traverse/{returnType}", "self"
: "http://localhost:7474/db/data/node/2", "property" :
"http://localhost:7474/db/data/node/2/properties/{key}",
"outgoing_typed_relationships" :
"http://localhost:7474/db/data/node/2/relationships/out/{-list|&|types}",
"properties" : "http://localhost:7474/db/data/node/2/properties",
"incoming_relationships" :
"http://localhost:7474/db/data/node/2/relationships/in", "extensions"
: { }, "create_relationship" :
"http://localhost:7474/db/data/node/2/relationships",
"paged_traverse" :
"http://localhost:7474/db/data/node/2/paged/traverse/{returnType}{?pageSize,leaseTime}",
"all_relationships" :
"http://localhost:7474/db/data/node/2/relationships/all",
"incoming_typed_relationships" :
"http://localhost:7474/db/data/node/2/relationships/in/{-list|&|types}"
} ]
Something to do when adding a item to a Dictionary when the key is null. Problem is, I don't see any nulls when I debug on my end, activity1 is there, RootNode is there, TypeKey is a const string.
I'm almost wondering if I should just keep the created nodes within a array or Dictionary myself and then just working with the NodeReference. That's what I'm going to try next.
Later that morning
This seems to load everything into the graph database fine:
var activityNodes = _activityTasks.GetAll().ToDictionary(a => a.Id, a => _graphClient.Create(a, new ActivityBelongsTo(_graphClient.RootNode)));
foreach (var p in _placeTasks.GetAll())
{
var placeNode = _graphClient.Create(p, new PlaceBelongsTo(_graphClient.RootNode));
foreach (var activity in p.Activities)
{
_graphClient.CreateRelationship(placeNode, new PlaceHasActivity(activityNodes[activity.Id]));
}
}
foreach (var u in _userTasks.GetAllUserGraph())
{
var userNode = _graphClient.Create(u, new UserBelongsTo(_graphClient.RootNode));
foreach(var activity in u.Activities)
{
_graphClient.CreateRelationship(userNode, new UserParticipatesIn(activityNodes[activity.Id]));
}
}
Now the problem is similar to what I had before. Now I want to get an activity that has a relationship to the RootNode:
Node<Activity> activity = _graphClient
.RootNode
.In<Activity>(ActivityBelongsTo.TypeKey, a => a.Id == 1)
.SingleOrDefault();
Throwing the key value can't be null exception again. I think I need to investigate the gremlin syntax more. I'm guessing the problem is there.
This afternoon
Started to experiment with Gremlin queries:
g.v(0).inE.filter{it.label=="ACTIVITY_BELONGS_TO"}.outV.filter{it.Id==1}.Name
works fine. I tried to replicate that using neo4jClient syntax:
_graphClient.RootNode.InE(ActivityBelongsTo.TypeKey).OutV(b => b.Id == 1).SingleOrDefault();
Same null exception, it spits out:
g.v(p0).inE.filter{ it[p1].equals(p2) }.outV.filter{ it[p3] == p4 }.drop(p5).take(p6)._()
which looks right to me, except for the end. Ran this though:
g.v(0).inE.filter{it.label=="ACTIVITY_BELONGS_TO"}.outV.filter{it.Id==1}.drop(0).take(1)._()
And that works fine. Something stinks here...maybe I should try the other library although I liked the de/serialization support. Sigh...
Thought maybe a raw query would work. Nope! This method no longer accepts a string and the required GremlinQuery I have no idea how to you. Grooooooooooooooooan.
var users = graphClient.ExecuteGetAllNodesGremlin<IsCustomer>("g.v(0).out('IsCustomer'){it.'Name' == 'BobTheBuilder'}");
Update 3/30/12
Created a new project, everything below works fine. Super confused why it will work here... :( Maybe version differences, I have no idea.
var client = new GraphClient(new Uri("http://localhost:7474/db/data"));
client.Connect();
client.Create(new User { Id = 1, Username = "joe" }, new UserBelongsTo(client.RootNode));
client.Create(new User { Id = 2, Username = "cloe" }, new UserBelongsTo(client.RootNode));
client.Create(new Activity { Id = 1, Name = "Bocce Ball" }, new ActivityBelongsTo(client.RootNode));
client.Create(new Activity { Id = 2, Name = "Programming" }, new ActivityBelongsTo(client.RootNode));
var user = client.RootNode.In<User>(UserBelongsTo.TypeKey, u=>u.Id == 1).SingleOrDefault();
var activity = client.RootNode.In<Activity>(ActivityBelongsTo.TypeKey, a=>a.Id == 1).SingleOrDefault();
client.CreateRelationship(user.Reference, new Plays(activity.Reference));
user = client.RootNode.In<User>(UserBelongsTo.TypeKey, u => u.Id == 1).SingleOrDefault();
activity = client.RootNode.In<Activity>(ActivityBelongsTo.TypeKey, a => a.Id == 1).SingleOrDefault();
I'm just getting started too. I would suggest you check out this blog:
http://romikoderbynew.com/2011/07/30/neo4jclient-primer/
Also, check http://frictionfree.org and its source code (in the about section) for more examples.
Creating relationships on existing - as I understand, this is possible. However, it appears to be easier to associate nodes as you create them. From the blog:
You can also create relationships between existing nodes.
graphClient.CreateRelationship(customerNodeReference, new
Speaks(languageNode.Reference));
RootNode - I believe you need to start a query from a node, I don't think you can do a
SELECT * FROM ... WHERE
Therefore, it would make sense that you need to attach nodes to the root node. This is an example from the FrictionFreeApp:
var node = graphClient.Create(
user,
new UserBelongsTo(rootNode));
Related
I have an ASP.NET MVC app using Entity Framework from our SQL Server backend.
Goal is to create ~18 WPackage entries via a foreach loop:
foreach (var dbitem in dbCList)
The code works for a single WPackage entry, but we have a request from the customer to create 300+ WPackages, so trying to use the Entity Framework code for a single "Add" and loop to create 300+ adds.
The T-SQL would be very challenging as there are many keys created on the fly/at row creation, so for activities >> resources, we'd have to insert the activity, grab or remember the activity key, then add resources with that newly created activity key.
Each WPackage (this is the main parent table) could have one or more of the following child table entries:
1+ activities
each activity would have 1+ resource
1+ budgets
1+ Signatures
1+ CostCodes
Our schema or model diagram would be:
WPackage
--Activities
-----Resources (child of Activities)
--CostCodes
--Budgets
--Signatures
The following code fails on:
dbContextTransaction.Commit();
with an error:
The transaction operation cannot be performed because there are pending requests working on this transaction.
[HttpPost]
public ActionResult Copy([Bind(Include = "ID,WBSID,...***fields excluded for brevity")] Package model)
{
if (ModelState.IsValid)
{
try
{
using (var dbContextTransaction = db.Database.BeginTransaction())
{
var dbCList = db.Packages.Join(db.WBS,
*expression omitted for brevity*)
// this dbClist will build about 18 items in the collection for below loop
foreach (var dbitem in dbCList)
{
int testWPID = dbitem;
WPackage prvWP = db.WPackages.Find(dbitem);
int previousWPID = dbitem;
WPackage previousWP = db.WPackages.Find(dbitem);
model.ID = dbitem;
db.WPackages.Add(model);
db.SaveChanges();
var budgets = db.Budgets.Where(i => i.WPID == previousWPID);
foreach (Budget budget in budgets)
{
budget.WPID = model.ID;
db.Budgets.Add(budget);
}
var costCodes = db.CostCodes.Where(i => i.WPID == previousWPID);
foreach (CostCode costCode in costCodes)
{
costCode.WPID = model.ID;
db.CostCodes.Add(costCode);
}
var activities = db.Activities.Where(i => i.WPID == previousWPID);
// *code excluded for brevity*
var previousActivityID = activity.ID;
db.Activities.Add(activity);
db.SaveChanges();
var resources = db.Resources.Where(i => i.ActivityID == previousActivityID);
foreach (Resource resource in resources)
{
resource.WPID = model.ID;
resource.ActivityID = activity.ID;
resource.ActivityNumber = activity.ActivityNumber;
db.Resources.Add(resource);
db.SaveChanges();
}
}
var signatures = db.RolesAndSigs
.Where(i => i.KeyId == previousWPID && i.Type == "WPL")
.OrderBy(i => i.Role)
.OrderBy(i => i.Person);
foreach (RolesAndSig signature in signatures)
{
db.RolesAndSigss.Add(signature);
}
db.SaveChanges();
dbContextTransaction.Commit();
}
}
}
}
I've also tried to have the Commit() run outside the foreach dbitem loop like:
db.SaveChanges();
//dbContextTransaction.Commit();
}
dbContextTransaction.Commit();
...but this returns error of:
[EXCEPTION] The property 'ID' is part of the object's key information and cannot be modified.
The code you posted has some issues that don't make sense, and probably aren't doing what you think they are doing. The crux of the issue you are facing is that Entity Framework tracks all references to entities it loads and associates:
Firstly this code:
int testWPID = dbitem;
WPackage prvWP = db.WPackages.Find(dbitem);
int previousWPID = dbitem;
WPackage previousWP = db.WPackages.Find(dbitem);
prvWP and previousWP will be pointing to the exact same reference, not two copies of the same entity. Be careful when updating either or any other reference retrieved or associated with that same ID. They all point to the same instance. If you do want a stand-alone snaphot reference you can use AsNoTracking().
Next, when you do something like this in a loop:
model.ID = dbitem;
db.WPackages.Add(model);
In the first iteration, "model" is not an entity. It is a deserialized block of data with the Type of the Package entity. As soon as you call .Add(model) that reference will now be pointing to a newly tracked entity reference. In the next loop you are telling EF to change that tracked entity reference's ID to a new value, and that is illegal.
What it looks like you want to do is create a copy of this model for each of the 18 expected iterations. For that what you want to do would be something more like:
foreach (var dbitem in dbCList)
{
var newModel = new WPackage
{
ID = dbItem,
WBSID = model.WBSID,
/// copy across all relevant fields from the passed in model.
};
db.WPackages.Add(newModel);
// ...
}
It would be quite worthwhile to leverage navigation properties for the related entities rather than using explicit joins and trying to scope everything in an explicit transaction with multiple SaveChanges() calls. EF can manage all of the FKs automatically rather than essentially using it as a wrapper for individual ADO CRUD operations.
You will need to be explicit between when you want to "clone" an object reference vs. "copy" a reference. For example, if I have a Customer that has an Address, and Addresses have a Country reference, when I clone a Customer, I will want to clone a new Address record for that Customer, however ensure that the Country reference is copied across. If I have a record for Jack at an 123 Apple Street, London in England, and go to clone Jack to make a record for Jill at the same address, they might be at the same location now, but not always, so I want them to point at different Address records in case Jill moves out. Still, there should only be one record for "England". (Jill may move to a different country, but her address record would just point at a different Country Id)
Wrong:
var jill = context.Customers.Single(c => c.Name == "Jack");
jill.Name = "Jill";
context.Customers.Add(jill);
This would attempt to rename Jack into Jill, then "Add" the already tracked instance, resulting in an exception.
Will work, but still Wrong:
var jack = context.Customers.AsNoTracking().Single(c => c.Name == "Jack");
var jill = jack;
jill.Name = "Jill";
context.Customers.Add(jill);
This would technically work by loading Jack as an untracked entity, and would save Jill as a new record with a new Id. However this is potentially very confusing. Depending on how the AddressId/Address is referenced we could end up with Jack and Jill referencing the same single Address record. Bad if you want Jack and Jill to have different addresses.
Right:
var jack = context.Customers
.Include(c => c.Address)
.ThenInclude(a => a.Country)
.Single(c => c.Name == "Jack");
var jill = new Customer
{
Name = "Jill",
// copy other fields...
Address = new Address
{
StreetNumber = jack.Address.StreetNumber,
StreetName = jack.Address.StreetName,
Country = jack.Address.Country
}
};
context.Customers.Add(jill);
The first detail is to ensure when we load Jack that we eager load all of the related details we will want to clone or copy references to. We then create a new instance for Jill, copying the values from Jack, including setting up a new Address record. The Country reference is copied across as there should only be ever a single record for "England".
Edit: For something like a roll-over scenario if you have a package by year, let's use the example of a Package class below:
public class Package
{
[Key]
public int PackageId { get; set; }
[ForeignKey("PackageType")]
public int PackageTypeId { get; set; }
public int Year { get; set; }
// .. More package related details and relationships...
public virtual PackageType PackageType { get; set; }
}
A goal might be to make a new Package and related data for Year 2022 from the data from 2021, and apply any changes from a view model passed in.
Find is a poor choice for this because Find wants to locate data by PK. If you're method simply passes an entity to be copied from (I.e. the data from 2021) then this can work, however if you have modified that data from 2021 to represent values you want for 2022 that could be dangerous or misleading within the code. (We don't want to update 2021's data, we want to create a new record set for 2022) To make a new Package for 2022 we just need the updated data to make up that new item, and a way to identify a source for what to use as a template. That identification could be the PK of the row to copy from (ProductId), or derived from the data passed in. (ProductTypeId, and Year-1) In both cases if we want to consider related data with the "copy from" product then it would be prudent to eager load that related data in one query rather than going back to the database repeatedly. Find cannot accommodate that.
For instance if I want to pass data to make a new product I pass a ProductTypeId, and a Year along with any values to use for the new structure. I can attempt to get a copy of the existing year to use as a template via:
var existingProduct = context.Products
.Include(x => x.Activities) // Eager load related data.
.Include(x => x.CostCodes)
// ...
.Single(x => x.ProductTypeId == productTypeId && x.Year = year - 1);
or if I passed a ProductId: (such as if I could choose to copy the data from a selected year like 2020 instead)
var existingProduct = context.Products
.Include(x => x.Activities)
.Include(x => x.CostCodes)
// ...
.Single(x => x.ProductId == copyFromProductId);
Both of these examples expect to find one, and only one existing product. If the request comes in with values that it cannot find a row for, there would be an exception which should be handled. This would fetch all of the existing product information that we can copy from, alongside any data that was passed into the method to create a new Product.
I'm trying to search for a collection of potential nodes but unable to do it...
I have a product that has a relationship with many instances. I would like to query the DB and get all the instances that are in a list that i get from the user.
Cypher:
var query = _context
.Cypher
.Start(new
{
instance = startBitsList,
product = productNode.Reference,
})
.Match("(product)-[:HasInstanceRel]->(instance)")
.Return(instance => instance.Node<ProductInstance>());
The problem is startBitsList... I use StringBuilder to generate a query that contains all the instances I'm looking for:
private static string CreateStartBits(IEnumerable<string> instanceNames)
{
var sb = new StringBuilder();
sb.AppendFormat("node:'entity_Name_Index'(");
foreach (var id in productIds)
{
sb.AppendFormat("Name={0} OR ", id);
}
sb.Remove(sb.Length - 4, 4);
sb.Append(")");
var startBitsList = sb.ToString();
return startBitsList;
}
I get exceptions when trying to run this cypher...
Is there a better way to search for multiple items that are stored in the collection I get from the user?
OK, I think there are a couple of issues at play here, first I'm presuming you are using Neo4j 1.9 and not 2.0 - hence using the .Start.
Have you tried taking your query and running it in Neo4j? This should be your first port of call, typically it's easy to add a breakpoint on the .Results call and add a 'watch' for query.Query.DebugText.
However, I don't think you need to use the StartBits the way you are, I think you'd be better off filtering with a .Where as you already have the start point:
private static ICypherFluentQuery CreateWhereClause(ICypherFluentQuery query, ICollection<string> instanceNames)
{
query = query.Where((Instance instance) => instance.Name == instanceNames.First());
query = instanceNames.Skip(1).Aggregate(query, (current, localInstanceName) => current.OrWhere((Instance instance) => instance.Name == localInstanceName));
return query;
}
and your query becomes something like:
var prodReference = new NodeReference<Product>(2);
var query =
Client.Cypher
.ParserVersion(1, 9)
.Start(new {product = prodReference})
.Match("(product)-[:HasInstanceRel]->(instance)");
query = CreateWhereClause(query, new[] {"Inst2", "Inst1"});
var resultsQuery = query.Return(instance => instance.As<Node<Instance>>());
2 things of note
We're not using the indexes - there is no benefit to using them as you have the start point and traversing to the 'instances' is a simple process for Neo4j.
The 'CreateWhereClause' method will probably go wrong if you pass in an empty list :)
The nice thing about not using the indexes is that - because they are legacy - you are set up better for Neo4j 2.0
Few days back I put a question regarding mapping two classes Message and MessageStatusHistory using EF. The mapping is going fine but I am facing some problems with the navigation property StatusHistory in class Message that relates it to MessageStatusHistory objects. I am loading the messages for one user only and want to the statuses pertaining to that user only. Like I would want to show if the user has marked message as read/not-read and when. If I use default loading mechanism like following it loads all the history related to the message irrespective of the user:
IDbSet<Message> dbs = _repo.DbSet;
dbs.Include("StatusHistory").Where(x=>x.MessageIdentifier == msgIdentifier);
To filter history for one user only I tried following trick:
IDbSet<Message> dbs = _repo.DbSet;
var q = from m in dbs.Include("StatusHistory")
where m.MessageIdentifier == msgIdentifier
select new Message
{
MessageIdentifier = m.MessageIdentifier,
/*OTHER PROPERTIES*/
StatusHistory = m.StatusHistory
.Where(x => x.UserId == userId).ToList()
};
return q.ToList();//THROWING ERROR ON THIS LINE
I am getting the error:
The entity or complex type 'MyLib.Biz.Message' cannot be constructed in a LINQ
to Entities query.
I have tried by commenting StatusHistory = m.StatusHistory.Where(x => x.UserId == userId).ToList() also but it has not helped.
Please help me in getting Messages with filtered StatusHistory.
EDIT:- above is resolved with this code:
var q = from m in _repository.DBSet.Include("Histories")
where m.MessageIdentifier == id
select new {
m.Id,/*OTHER PROPERTIES*/
Histories = m.Histories.Where(x =>
x.SenderId == userId).ToList()
};
var lst = q.ToList();
return lst.Select(m => new Message{
Id = m.Id, MessageIdentifier = m.MessageIdentifier,
MessageText = m.MessageText, Replies = m.Replies,
ReplyTo = m.ReplyTo, Histories = m.Histories, SenderId =
m.SenderId, SenderName = m.SenderName, CreatedOn = m.CreatedOn
}).ToList();
But if I try to include replies to the message with:
from m in _repository.DBSet.Include("Replies").Include("Histories")
I am getting error on converting query to List with q.ToList() for Histories = m.Histories.Where(x=> x.SenderId == userId).ToList().
About your EDIT part: You cannot use ToList() in a projection, just leave it an IEnumerable<T> and convert to a List<T> when you construct the Message. You also don't need to create two list objects, you can switch from the LINQ to Entities query to LINQ to Objects (the second Select) by using AsEnumerable():
var list = (from m in _repository.DBSet
where m.MessageIdentifier == id
select new {
// ...
Histories = m.Histories.Where(x => x.SenderId == userId)
})
.AsEnumerable() // database query is executed here
.Select(m => new Message {
// ...
Histories = m.Histories.ToList(),
// ...
}).ToList();
return list;
Be aware that Include has no effect when you use a projection with select. You need to make the properties that you want to include part of the projection - as you already did with select new { Histories.....
I'm designing an interface where the user can join a publicaiton to a keyword, and when they do, I want to suggest other keywords that commonly occur in tandem with the selected keyword. The trick is getting the frequency of correlation alongside the properties of the suggested keywords.
The Keyword type (EF) has these fields:
int Id
string Text
string UrlString
...and a many-to-many relation to a Publications entity-set.
I'm almost there. With :
var overlappedKeywords =
selectedKeyword.Publications.SelectMany(p => p.Keywords).ToList();
Here I get something very useful: a flattened list of keywords, each duplicated in the list however many times it appears in tandem with selectedKeyword.
The remaining Challenge:
So I want to get a count of the number of times each keyword appears in this list, and project the distinct keyword entities onto a new type, called KeywordCounts, having the same fields as Keyword but with one extra field: int PublicationsCount, into which I will populate the count of each Keyword within overlappedKeywords. How can I do this??
So far I've tried 2 approaches:
var keywordCounts = overlappingKeywords
.Select(oc => new KeywordCount
{
KeywordId = oc.Id,
Text = oc.Text,
UrlString = oc.UrlString,
PublicationsCount = overlappingKeywords.Count(ok2 => ok2.Id == oc.Id)
})
.Distinct();
...PublicationsCount is getting populated correctly, but Distinct isn't working here. (must I create an EqualityComarer for this? Why doesn't the default EqualityComarer work?)
var keywordCounts = overlappingKeywords
.GroupBy(o => o.Id)
.Select(c => new KeywordCount
{
Id = ???
Text = ???
UrlString = ???
PublicationsCount = ???
})
I'm not very clear on GroupBy. I don't seem to have any access to 'o' in the Select, and c isn't comping up with any properties of Keyword
UPDATE
My first approach would work with a simple EqualityComparer passed into .Distinct() :
class KeywordEqualityComparer : IEqualityComparer<KeywordCount>
{
public bool Equals(KeywordCount k1, KeywordCount k2)
{
return k1.KeywordId== k2.KeywordId;
}
public int GetHashCode(KeywordCount k)
{
return k.KeywordId.GetHashCode();
}
}
...but Slauma's answer is preferable (and accepted) because it does not require this. I'm still stumped as to what the default EqualityComparer would be for an EF entity instance -- wouldn't it just compare based on primary ids, as I did above here?
You second try is the better approach. I think the complete code would be:
var keywordCounts = overlappingKeywords
.GroupBy(o => o.Id)
.Select(c => new KeywordCount
{
Id = c.Key,
Text = c.Select(x => x.Text).FirstOrDefault(),
UrlString = c.Select(x => x.UrlString).FirstOrDefault(),
PublicationsCount = c.Count()
})
.ToList();
This is LINQ to Objects, I guess, because there doesn't seem to be a EF context involved but an object overlappingKeywords, so the grouping happens in memory, not in the database.
I'm quite new to linq, so please bear with me.
I'm working on a asp.net webpage and I want to add a "search function" (textbox where user inputs name or surname or both or just parts of it and gets back all related information). I have two tables ("Person" and "Application") and I want to display some columns from Person (name and surname) and some from Application (score, position,...). I know how I could do it using sql, but I want to learn more about linq and thus I want to do it using linq.
For now I got two main ideas:
1.)
var person = dataContext.GetTable<Person>();
var application = dataContext.GetTable<Application>();
var p1 = from p in Person
where(p.Name.Contains(tokens[0]) || p.Surname.Contains(tokens[1]))
select new {Id = p.Id, Name = p.Name, Surname = p.Surname}; //or maybe without this line
//I don't know how to do the following properly
var result = from a in Application
where a.FK_Application.Equals(index) //just to get the "right" type of application
//this is not right, but I don't know how to do it better
join p1
on p1.Id == a.FK_Person
2.) The other idea is just to go through "Application" and instead of "join p1 ..." to use
var result = from a in Application
where a.FK_Application.Equals(index) //just to get the "right" type of application
join p from Person
on p.Id == a.FK_Person
where p.Name.Contains(tokens[0]) || p.Surname.Contains(tokens[1])
I think that first idea is better for queries without the first "where" condition, which I also intended to use. Regardless of what is better (faster), I still don't know how to do it using linq. Also in the end I wanted to display / select just some parts (columns) of the result (joined tables + filtering conditions).
I really want to know how to do such things using linq as I'll be dealing also with some similar problems with local data, where I can use only linq.
Could somebody please explain me how to do it, I spent days trying to figure it out and searching on the Internet for answers.
var result = from a in dataContext.Applications
join p in dataContext.Persons
on p.Id equals a.FK_Person
where (p.Name.Contains("blah") || p.Surname.Contains("foo")) && a.FK_Application == index
select new { Id = p.Id, Name = p.Name, Surname = p.Surname, a.Score, a.Position };
Well as Odrahn pointed out, this will give you flat results, with possibly many rows for a single person, since a person could join on multiple applications that all have the same FK. Here's a way to search all the right people, and then add on the relevant application to the results:
var p1 = from p in dataContext.Persons
where(p.Name.Contains(tokens[0]) || p.Surname.Contains(tokens[1]))
select new {
Id = p.Id, Name = p.Name, Surname = p.Surname,
BestApplication = dataContext.Applications.FirstOrDefault(a => a.FK_Application == index /* && ???? */);
};
Sorry - it looks like this second query will result in a roundtrip per person, so it clearly won't be scalable. I assumed L2S would handle it better.
In order to answer this properly, I need to know if Application and Person are directly related (i.e. does Person have many Applications)? From reading your post, I'm assuming that they are because Application seems to have a foreign key to person.
If so, then you could create a custom PersonModel which will be populated by the fields you need from the different entities like this:
class PersonModel
{
string Name { get; set; }
string Surname { get; set; }
List<int> Scores { get; set; }
List<int> Positions { get; set; }
}
Then to populate it, you'd do the following:
// Select the correct person based on Name and Surname inputs
var person = dataContext.Persons.Where(p => p.Name.Contains("firstname") || p.Name.Contains("surname")).FirstOrDefault();
// Get the first person we find (note, there may be many - do you need to account for this?)
if (person != null)
{
var scores = new List<int>();
var positions = new List<int>();
scores.AddRange(person.Applications.Select(i => i.Score);
positions.AddRange(person.Applications.Select(i => i.Position);
var personModel = new PersonModel
{
Name = person.Name,
Surname = person.Surname,
Scores = scores,
Positions = positions
};
}
Because of your relationship between Person and Application, where a person can have many applications, I've had to account for the possibility of there being many scores and positions (hence the List).
Also note that I've used lambda expressions instead of plain linqToSql for simple selecting so that you can visualise easily what's going on.