I am starting to investigate the use of Neo4j using the neo4client API.
I have created a basic database, and can query it using the web client. I am now trying to build a sample C# interface. I am having some problems with index lookups. My database consists of nodes with two properties: conceptID and fullySpecifiedName. Auto-indexing is enabled, and both node properties are listed in the node_keys_indexable property of neo4j.properties.
I keep getting IntelliSense errors in my C# when using the Node class. It appears to be defined as Node<T>, but I don't know what to supply as the value of the type. Consider this example from this forum...
var result = _graphClient
.Cypher
.Start(new
{
n = Node.ByIndexLookup("index_name", "key_name", "Key_value")
})
.Return((n) => new
{
N = n.Node<Item>()
})
.Results
.Single();
var n = result.N;
Where does the "Item" in Node<Item> come from?
I have deduced that the index name I should use is node_auto_index, but I can't figure out a default node type.
Item is the type of node you have stored in the DB, so if you have you're storing a class:
public class MyType { public int conceptId { get; set; } public string fullySpecifiedName { get;set; } }
You would be retrieving Node<MyType> back.
Simple flow:
//Store a 'MyType'
_graphClient.Create(new MyType{conceptId = 1, fullySpecifiedName = "Name");
//Query MyType by Index
var query =
_graphClient.Cypher
.Start(new { n = Node.ByIndexLookup("node_auto_index", "conceptId", 1)
.Return<Node<MyType>>("n");
Node<MyType> result = query.Results.Single();
//Get the MyType instance
MyType myType = result.Data;
You can bypass the result.Data step by doing .Return<MyType>("n") instead of Node<MyType> as you'll just get an instance of MyType in that case.
Related
I'm trying to access a class value by using a variable previously defined in dart, but I keep getting the error the operator [] isn't defined for the class
In Javascript I would access an object value using a variable like this:
let movie = {
movieTitle : 'Toy Story',
actor: 'Tom Hanks'
}
let actorName = 'actor';
console.log(movie[actorName]); // <- what I'm trying to replicate in dart
// expected output: Tom Hanks
Here is what I've tried and is throwing that error
class Movie {
String name;
String actor;
String producer;
}
void main() {
var movieTitle = new Movie();
movieTitle.name = 'Toy Story';
movieTitle.actor = 'Tom Hanks';
print(movieTitle.actor); <- prints out Tom Hanks as expected
var actorName = 'actor';
print(movieTitle[actorName]); <- throws error
}
I expect to be able to use a variable on the fly to access the value.
A trivial use case for me would be if I had a a list of Movie classes, where some actors and producers are null, I would like to filter on either non null actors or producer with a function like so:
List values = movieList.where((i) => i.actor != "null").toList(); // returns all Movies in movieList where the actor value isn't the string "null"
var actorIsNull = 'actor';
List values = movieList.where((i) => i[actorisNull] != "null").toList(); // throws error
You can createn a toMap() function in your Movie class and access properties using [] operator
class Movie {
String name;
String actor;
String producer;
Map<String, dynamic> toMap() {
return {
'name': name,
'actor' : actor,
'producer' : producer,
};
}
}
Now Movie class properties can be accessed as:
Movie movie = Movie();
movie.toMap()['name'];
You cannot access class members by a string containing their name. (Except with mirrors - outside the scope of this answer.)
You could remove the class altogether and just use a Map<String, String>.
Map<String, String> movie = {
'movieTitle': 'Toy Story',
'actor': 'Tom Hanks',
}
You could add some bool methods on the class.
bool hasNoActor() => actor == null;
...
List values = movieList.where((m) => !m.hasNoActor()).toList();
Or, you could pass a lambda to your mapper.
Movie movieTitle = Movie()
..name = 'Toy Story'
..actor = 'Tom Hanks';
Function hasActor = (Movie m) => m.actor != null;
List values = movieList.where(hasActor).toList();
I have the below example.
I was wondering what is the best and quickest way to add a list of nodes and edges in a single transaction? I use standard C# Neo4j .NET packages but open to the Neo4jClient as I've read that's faster. Anything that supports .NET and 4.5 to be honest.
I have an lists of about 60000 FooA objects that need to be added into Neo4j and it can take hours!
Firstly, FooB objects hardly change so I don't have to add them everyday. The performance issues is with adding new FooA objects twice a day.
Each FooA object has a list of FooB objects has two lists containing the relationships I need to add; RelA and RelB (see below).
public class FooA
{
public long Id {get;set;} //UniqueConstraint
public string Name {get;set;}
public long Age {get;set;}
public List<RelA> ListA {get;set;}
public List<RelB> ListB {get;set;}
}
public class FooB
{
public long Id {get;set;} //UniqueConstraint
public string Prop {get;set;}
}
public class RelA
{
public string Val1 {get;set;}
pulic NodeTypeA Node {get;set;
}
public class RelB
{
public FooB Start {get;set;}
public FooB End {get;set;}
public string ValExample {get;set;}
}
Currently, I check if Node 'A' exists by matching by Id. If it does then I completely skip and move onto the next item. If not, I create Node 'A' with its own properties. I then create the edges with their own unique properties.
That's quite a few transactions per item. Match node by Id -> add nodes -> add edges.
foreach(var ntA in FooAList)
{
//First transaction.
MATCH (FooA {Id: ntA.Id)})
if not exists
{
//2nd transaction
CREATE (n:FooA {Id: 1234, Name: "Example", Age: toInteger(24)})
//Multiple transactions.
foreach (var a in ListA)
{
MATCH (n:FooA {Id: ntA.Id}), (n2:FooB {Id: a.Id }) with n,n2 LIMIT 1
CREATE (n)-[:RelA {Prop: a.Val1}]-(n2)
}
foreach (var b in Listb)
{
MATCH (n:FooB {Id: b.Start.Id}), (n2:FooB {Id: b.End.Id }) with n,n2 LIMIT 1
CREATE (n)-[:RelA {Prop: b.ValExample}]-(n2)
}
}
How would one go about adding a list of FooA's using for example Neo4jClient and UNWIND or any other way apart from CSV import.
Hope that makes sense, and thanks!
The biggest problem is the nested lists, which mean you have to do your foreach loops, so you end up executing a minimum of 4 queries per FooA, which for 60,000 - well - that's a lot!
Quick Note RE: Indexing
First and foremost - you need an index on the Id property of your FooA and FooB nodes, this will speed up your queries dramatically.
I've played a bit with this, and have it storing 60,000 FooA entries, and creating 96,000 RelB instances in about 12-15 seconds on my aging computer.
The Solution
I've split it into 2 sections - FooA and RelB:
FooA
I've had to normalise the FooA class into something I can use in Neo4jClient - so let's introduce that:
public class CypherableFooA
{
public CypherableFooA(FooA fooA){
Id = fooA.Id;
Name = fooA.Name;
Age = fooA.Age;
}
public long Id { get; set; }
public string Name { get; set; }
public long Age { get; set; }
public string RelA_Val1 {get;set;}
public long RelA_FooBId {get;set;}
}
I've added the RelA_Val1 and RelA_FooBId properties to be able to access them in the UNWIND. I convert your FooA using a helper method:
public static IList<CypherableFooA> ConvertToCypherable(FooA fooA){
var output = new List<CypherableFooA>();
foreach (var element in fooA.ListA)
{
var cfa = new CypherableFooA(fooA);
cfa.RelA_FooBId = element.Node.Id;
cfa.RelA_Val1 = element.Val1;
output.Add(cfa);
}
return output;
}
This combined with:
var cypherable = fooAList.SelectMany(a => ConvertToCypherable(a)).ToList();
Flattens the FooA instances, so I end up with 1 CypherableFooA for each item in the ListA property of a FooA. e.g. if you had 2 items in ListA on every FooA and you have 5,000 FooA instances - you would end up with cypherable containing 10,000 items.
Now, with cypherable I call my AddFooAs method:
public static void AddFooAs(IGraphClient gc, IList<CypherableFooA> fooAs, int batchSize = 10000, int startPoint = 0)
{
var batch = fooAs.Skip(startPoint).Take(batchSize).ToList();
Console.WriteLine($"FOOA--> {startPoint} to {batchSize + startPoint} (of {fooAs.Count}) = {batch.Count}");
if (batch.Count == 0)
return;
gc.Cypher
.Unwind(batch, "faItem")
.Merge("(fa:FooA {Id: faItem.Id})")
.OnCreate().Set("fa = faItem")
.Merge("(fb:FooB {Id: faItem.RelA_FooBId})")
.Create("(fa)-[:RelA {Prop: faItem.RelA_Val1}]->(fb)")
.ExecuteWithoutResults();
AddFooAs(gc, fooAs, batchSize, startPoint + batch.Count);
}
This batches the query into batches of 10,000 (by default) - this takes about 5-6 seconds on mine - about the same as if I try all 60,000 in one go.
RelB
You store RelB in your example with FooA, but the query you're writing doesn't use the FooA at all, so what I've done is extract and flatten all the RelB instances in the ListB property:
var relBs = fooAList.SelectMany(a => a.ListB.Select(lb => lb));
Then I add them to Neo4j like so:
public static void AddRelBs(IGraphClient gc, IList<RelB> relbs, int batchSize = 10000, int startPoint = 0)
{
var batch = relbs.Select(r => new { StartId = r.Start.Id, EndId = r.End.Id, r.ValExample }).Skip(startPoint).Take(batchSize).ToList();
Console.WriteLine($"RELB--> {startPoint} to {batchSize + startPoint} (of {relbs.Count}) = {batch.Count}");
if(batch.Count == 0)
return;
var query = gc.Cypher
.Unwind(batch, "rbItem")
.Match("(fb1:FooB {Id: rbItem.StartId}),(fb2:FooB {Id: rbItem.EndId})")
.Create("(fb1)-[:RelA {Prop: rbItem.ValExample}]->(fb2)");
query.ExecuteWithoutResults();
AddRelBs(gc, relbs, batchSize, startPoint + batch.Count);
}
Again, batching defaulted to 10,000.
Obviously time will vary depending on the number of rels in ListB and ListA - My tests has one item in ListA and 2 in ListB.
This question already has answers here:
Working with C# Anonymous Types
(8 answers)
Closed 8 years ago.
I am using ASP.NET mvc 5. I have one class that holds all the LINQ which can access to another class. now i convert the LINQ query to list variable Query and returning as IList... the i create object of this class--> call the method and get result.
now i can see in debugging object names but i can't see in foreach loop. my list hold mix data types, plus result is merging from different tables...
public IList GetAllFeeZonesForFeeSchemeByID(int FeeSchemeID)
{
using (var db = new QualificationContext())
{
var Query = from a in db.FeeScheme
join b in db.FeeZoneSchema.Where(c => c.FeeSchemeID == 1) on a.FeeSchemeID equals b.FeeSchemeID
join c in db.FeeZone on b.FeeZoneID equals c.FeeZoneID
select new
{
FeeScheme = a.FeeSchemeID,
FeeZone = b.FeeZoneID,
FeeZone_Description = c.FeeZoneDescription
};
return Query.ToList();
}
}
in controller class...
foreach(var item in obj1.GetAllFeeZonesForFeeSchemeByID(1))
{
item.???? (can't access the object here....
}
many thanks
You should return Generic IList of concrete (not anonymous class):
public IList<FeeSchemeModel> GetAllFeeZonesForFeeSchemeByID(int FeeSchemeID)
{
using (var db = new QualificationContext())
{
var Query = from a in db.FeeScheme
join b in db.FeeZoneSchema.Where(c => c.FeeSchemeID == 1) on a.FeeSchemeID equals b.FeeSchemeID
join c in db.FeeZone on b.FeeZoneID equals c.FeeZoneID
select new FeeSchemeModel
{
FeeScheme = a.FeeSchemeID,
FeeZone = b.FeeZoneID,
FeeZone_Description = c.FeeZoneDescription
};
return Query.ToList();
}
}
public class FeeSchemeModel
{
public int FeeScheme{get;set;}
public int FeeZone{get;set;}
public string FeeZone_Description{get;set;}
};
But I recommend to use IEnumerable<T> instead of IList<T> and use ToArray() method instead of ToList() method if you don't use special features of List<T> (such as method Add())
IList is non-generic interface, it contains only non-generic IEnumerable definition, which enumerates objects. So type of item will be object. That's why you can see only members of System.Object class.
You should either cast item to appropriate type or use generic collection parametrized with appropriate type. But you can't use neither of these approaches while you are using anonymous objects, because you don't know anonymous type name. So, you need to create some class which you will be able to cast to:
foreach(Foo item in obj1.GetAllFeeZonesForFeeSchemeByID(1))
Or use as parameter of method return type:
public IList<Foo> GetAllFeeZonesForFeeSchemeByID(int FeeSchemeID)
One more option is usage of dynamic type, which will resolve operations on object at runtime. You still will not be able to use IntelliSense but your code will work:
foreach(dynamic item in obj1.GetAllFeeZonesForFeeSchemeByID(1))
{
// use item.FeeScheme
}
Some background
I'm wanting to bind a list of objects (my model-view) to a grid. The model-view contains fields for both an specific entity and fields from a joined entity.
I was getting an error when I would try to bind due to the dbContext being out of scope. I realized I needed to use the .Include() method in order to eager load my navigation property. However, I suspect that since I'm using Linq to Entities, that I'm now generating another error:
"Unable to cast the type 'System.Linq.IQueryable1' to type 'System.Data.Objects.ObjectQuery1'. LINQ to Entities only supports casting EDM primitive or enumeration types."
My code is shown below, any ideas of what I need to do here?
Thanks in advance!
public static List<PlanViewModel> GetPlans()
{
using (var context = new RepEntities())
{
var query = (from p in context.Plans
join r in context.RealEstateDetails on p.ReId equals r.ReId
select new PlanViewModel
{
PlanName = p.PlanName,
TargetCompletionDate = p.TargetCompletionDate,
ActualCompletionDate = p.ActualCompletionDate,
Provision = p.Provision,
StatusTypeId = p.StatusTypeId,
StatusCommon = p.StatusCommon,
Building = r.BuildingName,
City = r.City,
Country = r.Country
}).Include("StatusCommon");
return query.ToList();
}
}
You are almost there, just put Include("StatusCommon") right after context.Plans. Because you need to include StatusCommon before the iteration, this way you can set StatusCommon value for every iteration.
public static List<PlanViewModel> GetPlans()
{
using (var context = new RepEntities())
{
var query = (from p in context.Plans.Include("StatusCommon")
join r in context.RealEstateDetails on p.ReId equals r.ReId
select new PlanViewModel
{
PlanName = p.PlanName,
TargetCompletionDate = p.TargetCompletionDate,
ActualCompletionDate = p.ActualCompletionDate,
Provision = p.Provision,
StatusTypeId = p.StatusTypeId,
StatusCommon = p.StatusCommon,
Building = r.BuildingName,
City = r.City,
Country = r.Country
}).toList();
return query;
}
}
var result =
(from bd in context.tblBasicDetails
from pd in context.tblPersonalDetails.Where(x => x.UserId == bd.UserId).DefaultIfEmpty()
from opd in context.tblOtherPersonalDetails.Where(x => x.UserId == bd.UserId).DefaultIfEmpty()
select new clsProfileDate()
{
DOB = pd.DOB
});
foreach (clsProfileDate prod in result)
{
prod.dtDOB = !string.IsNullOrEmpty(prod.DOB) ? Convert.ToDateTime(prod.DOB) : DateTime.Today;
int now = int.Parse(DateTime.Today.ToString("yyyyMMdd"));
int dob = int.Parse(prod.dtDOB.ToString("yyyyMMdd"));
string dif = (now - dob).ToString();
string age = "0";
if (dif.Length > 4)
age = dif.Substring(0, dif.Length - 4);
prod.Age = Convert.ToInt32(age);
}
GetFinalResult(result);
protected void GetFinalResult(IQueryable<clsProfileDate> result)
{
int from;
bool bfrom = Int32.TryParse(ddlAgeFrom.SelectedValue, out from);
int to;
bool bto = Int32.TryParse(ddlAgeTo.SelectedValue, out to);
result = result.AsQueryable().Where(p => p.Age >= from);
}
Here I am getting an exception:
The specified type member "Age" is not supported in LINQ to Entities.
Only initializers, entity members, and entity navigation properties
are supported.
Where Age is not in database it is property I created in clsProfileDate class to calculate Age from DOB. Any solution to this?
You cannot use properties that are not mapped to a database column in a Where expression. You must build the expression based on mapped properties, like:
var date = DateTime.Now.AddYears(-from);
result = result.Where(p => date >= p.DOB);
// you don't need `AsQueryable()` here because result is an `IQueryable` anyway
As a replacement for your not mapped Age property you can extract this expression into a static method like so:
public class clsProfileDate
{
// ...
public DateTime DOB { get; set; } // property mapped to DB table column
public static Expression<Func<clsProfileDate, bool>> IsOlderThan(int age)
{
var date = DateTime.Now.AddYears(-age);
return p => date >= p.DOB;
}
}
And then use it this way:
result = result.Where(clsProfileDate.IsOlderThan(from));
A lot of people are going to say this is a bad answer because it is not best practice but you can also convert it to a List before your where.
result = result.ToList().Where(p => date >= p.DOB);
Slauma's answer is better, but this would work as well. This cost more because ToList() will execute the Query against the database and move the results into memory.
You will also get this error message when you accidentally forget to define a setter for a property.
For example:
public class Building
{
public string Description { get; }
}
var query =
from building in context.Buildings
select new
{
Desc = building.Description
};
int count = query.ToList();
The call to ToList will give the same error message. This one is a very subtle error and very hard to detect.
I forgot to select the column (or set/map the property to a column value):
IQueryable<SampleTable> queryable = from t in dbcontext.SampleTable
where ...
select new DataModel { Name = t.Name };
Calling queryable.OrderBy("Id") will throw exception, even though DataModel has property Id defined.
The correct query is:
IQueryable<SampleTable> queryable = from t in dbcontext.SampleTable
where ...
select new DataModel { Name = t.Name, Id = t.Id };
In my case, I was getting this error message only in Production but not when run locally, even though my application's binaries were identical.
In my application, I'm using a custom DbModelStore so that the runtime-generated EDMX is saved to disk and loaded from disk on startup (instead of regenerating it from scratch) to reduce application startup time - and due to a bug in my code I wasn't invalidating the EDMX file on-disk - so Production was using an older version of the EDMX file from disk that referenced an older version of my application's types from before I renamed the type-name in the exception error message.
Deleting the cache file and restarting the application fixed it.
Advanced answer:
Search in edmx file EntitySetMapping and check if the field is mapped to a column in database:
<EntitySetMapping Name="MY_TABLE">
<EntityTypeMapping TypeName="MYMODEL.MY_TABLE">
<MappingFragment StoreEntitySet="MY_TABLE">
<ScalarProperty Name="MY_COLUMN" ColumnName="MY_COLUMN_NAME" />
</MappingFragment>
</EntityTypeMapping>
</EntitySetMapping>
I was having this problem because the edmx had changes I didn't want and through git I discarded too many changes...
Checking Count() before the WHERE clause solved my problem. It is cheaper than ToList()
if (authUserList != null && _list.Count() > 0)
_list = _list.Where(l => authUserList.Contains(l.CreateUserId));