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How do I join to a second mongo collection to a child document using Linq

I have two collections - accounts and users. Logically, they have a many-to-many relationship. In mongo, they look like this:
users
[
{
"userId": "3Nv6yHTC6Eiq0SaMyBcDlA",
"emailAddress": "foo#bar.com",
"userAccounts":
[
{
"accountId": "tgvANZWSZkWl0bAOM00IBw"
}
]
}
]
accounts
[
{
"accountId": "tgvANZWSZkWl0bAOM00IBw",
"accountCode": "foo",
"userIds":
[
"3Nv6yHTC6Eiq0SaMyBcDlA"
]
}
]
Can I use a single Linq operation using the mongo Linq driver to join the account collection to the user's userAccounts child documents, such that I return a user (or list of users) with the accountCode included within each userAccount (the ExtendedUserAccount within the ExtendedUser in the example below)? Or do I need to forget Linq and use the Aggregate class instead?
The query below results in an ExpressionNotSupportedExpression from the mongo Linq driver. If I split the query to get the user first and then join to the accounts collection, it works.
Here is some code!
using MongoDB.Bson.Serialization.Conventions;
using MongoDB.Driver;
using MongoDB.Driver.Linq;
var settings = MongoClientSettings.FromConnectionString("yourconnectionstring");
settings.LinqProvider = MongoDB.Driver.Linq.LinqProvider.V3;
var client = new MongoClient(settings);
var conventionPack = new ConventionPack { new CamelCaseElementNameConvention(), new IgnoreExtraElementsConvention(true) };
ConventionRegistry.Register("camelCase", conventionPack, t => true);
var db = client.GetDatabase("Test");
var accountCollection = db.GetCollection<Account>("accounts");
var userCollection = db.GetCollection<User>("users");
var queryableAccounts = accountCollection.AsQueryable();
var extendedUser = userCollection.AsQueryable()
.Where(u => u.EmailAddress == "foo#bar.com")
.Select(u => new ExtendedUser(
u.UserId,
u.EmailAddress,
u.UserAccounts.Join(
queryableAccounts,
ua => ua.AccountId,
a => a.AccountId,
(ua, a) => new ExtendedUserAccount(a.AccountCode, ua.AccountId)))
)
.FirstOrDefault();
Console.WriteLine(extendedUser);
public record class User(string UserId, string EmailAddress, IEnumerable<UserAccount> UserAccounts);
public record class UserAccount(string AccountId);
public record class Account(string AccountId, string AccountCode, IEnumerable<string> UserIds);
public record class ExtendedUser(string UserId, string EmailAddress, IEnumerable<ExtendedUserAccount> UserAccounts);
public record class ExtendedUserAccount(string AccountId, string AccountCode);

I tested even with LinqProviderV3 setting on MongoClientSettings, but sadly to say that the MongoDB .Net Driver seems doesn't support it (sub-query join).
You should look for .Aggregate().
MongoDB query
db.users.aggregate([
{
$match: {
emailAddress: "foo#bar.com"
}
},
{
$lookup: {
from: "accounts",
localField: "userAccounts.accountId",
foreignField: "accountId",
pipeline: [
{
$project: {
_id: 0,
accountId: 1,
accountCode: 1
}
}
],
as: "userAccounts"
}
}
])
Approach 1: Pass the query as BsonDocument
Either you can translate the above query (the array part) to BsonDocument[] with the help of MongoDB Compass. It should be as below:
var pipeline = new BsonDocument[]
{
new BsonDocument("$match",
new BsonDocument("emailAddress", "foo#bar.com")),
new BsonDocument("$lookup",
new BsonDocument
{
{ "from", "accounts" },
{ "localField", "userAccounts.accountId" },
{ "foreignField", "accountId" },
{ "pipeline",
new BsonArray
{
new BsonDocument("$project",
new BsonDocument
{
{ "_id", 0 },
{ "accountId", 1 },
{ "accountCode", 1 }
})
} },
{ "as", "userAccounts" }
})
};
var extendedUser = userCollection.Aggregate<ExtendedUser>(pipeline)
.FirstOrDefault();
Approach 2: Working with Aggregate Fluent
var lookupPipeline = new EmptyPipelineDefinition<Account>()
.Match(new BsonDocument("$expr",
new BsonDocument("$in", new BsonArray { "$accountId", "$$accountId" })
))
.Project<Account, Account, ExtendedUserAccount>(
Builders<Account>.Projection
.Include(x => x.AccountId)
.Include(x => x.AccountCode));
var extendedUser = userCollection.Aggregate()
.Match(u => u.EmailAddress == "foo#bar.com")
.Lookup(accountCollection,
new BsonDocument { { "accountId", "$userAccounts.accountId" } },
lookupPipeline,
new ExpressionFieldDefinition<ExtendedUser, IEnumerable<ExtendedUserAccount>>(x => x.UserAccounts)
)
.FirstOrDefault();
Similar usage for MongoDB.Driver.Tests AggregateFluentTest
Demo

c# - Update unit test method with Moq

I am using the Moq framework for my unit test.
This is my TestMethod:
[TestFixture]
public class UpdateContactTests
{
private static readonly object[] TestValidContact =
{
new object[]
{
"Prueba", "nearlinx#gmail.com", "86456245",
new LookUpItem()
{
LookUpItemId = Guid.NewGuid(), Category = "ContactType", CategoryId = 1, Value = "Bulling Contact"
},
new Company()
{
Id = Guid.NewGuid(), Name = "Company", Email = "company#gmail.com", WebSite = "company.com",
Nda = false, Msa = false, Phone = "84876817"
}
}
};
[TestCaseSource(nameof(TestValidContact))]
[Test]
public void UpdateContact_ValidValues_UpdateContact(string name, string email, string phone, LookUpItem lookUpItem, Company company)
{
//arrange
var id = Guid.NewGuid();
var data =
new[]
{
new Contact { Id = Guid.NewGuid(), Name = "Test1", Email = "nearlinx#gmail.com", Phone = "86456245",
ContactType =
new LookUpItem()
{
LookUpItemId = Guid.NewGuid(), Category = "ContactType", CategoryId = 1, Value = "Bulling Contact"
},
Company =
new Company()
{
Id = Guid.NewGuid(), Name = "Company", Email = "company#gmail.com", WebSite = "company.com",
Nda = false, Msa = false, Phone = "84876817"
}},
new Contact { Id = id, Name = "Test2", Email = "nearlinx#gmail.com", Phone = "86456245",
ContactType =
new LookUpItem()
{
LookUpItemId = Guid.NewGuid(), Category = "ContactType", CategoryId = 1, Value = "Bulling Contact"
},
Company =
new Company()
{
Id = Guid.NewGuid(), Name = "Company", Email = "company#gmail.com", WebSite = "company.com",
Nda = false, Msa = false, Phone = "84876817"
}},
};
var contact = new Contact()
{
Id = id,
Name = name,
Email = email,
Phone = phone,
ContactType = lookUpItem,
Company = company
};
var _unitOfWork = new Mock<IUnitOfWork>();
_unitOfWork.Setup(mock => mock.Contact.Get(null, null, null)).Returns(data);
_unitOfWork.Setup(mock => mock.Company.Get(null, null, null)).Returns(new List<Company>());
_unitOfWork.Setup(mock => mock.LookUpItem.Get(null, null, null)).Returns(new List<LookUpItem>());
var contactService = new ContactService(_unitOfWork.Object);
//act
contactService.UpdateContact(contact);
//assert
Assert.That(data.First(m => m.Id == id).Name, Is.EqualTo(contact.Name));
_unitOfWork.Verify(mock => mock.Contact.Update(It.IsAny<Contact>()), Times.Once);
}
}
My problem is that when I run the test a NullReferenceException is thrown, I suppose it is because the list that has the object that I want to modify is not being assigned
I've never really used Moq and I don't know much about unit tests either, so what am I really doing wrong
Edit:
i change one of the setup because the one called when the update is done was another
instead of
_unitOfWork.Setup(mock => mock.Contact.Get(null, null, null)).Returns(data);
is
_unitOfWork.Setup(mock => mock.Contact.Where(c => c.Id == contact.Id,null,null).FirstOrDefault()).Returns(() => data.Where(c => c.Id == contact.Id));

Without seeing the rest
_unitOfWork.Setup(mock => mock.Contact.Get(null, null, null))
the mock.Contact returns null
best thing is to debug the test, breakpoint the first line and step through to find exactly where it is throwing the null exception

I found the solution
I was doing the set like this
_unitOfWork.Setup(mock => mock.Contact.Where(c => c.Id == contact.Id,null,null).FirstOrDefault()).Returns(() => data.Where(c => c.Id == contact.Id));
while in the update method the condition was this
_unitOfWork.Setup(mock => mock.Contact.Where(c => c.Id == contact.Id).FirstOrDefault()).Returns(() => data.Where(c => c.Id == contact.Id));
changing the condition in the method fixed the problem

How to Select only Id's with linq when there is List in List

I want to select only id's from List of objects in another List:
https://dotnetfiddle.net/Leu1AD
I need to use only linq Select or SelectMany:
var obj = offices.Select(p => new {Id = p.Id, Employess = p.Employess}).ToList();
Currently I get following result:
[
{
"Id":1,
"Employess":[
{
"Id":1,
"FirstName":"a",
"LastName":"b"
},
{
"Id":2,
"FirstName":"c",
"LastName":"d"
}
]
},
{
"Id":2,
"Employess":[
{
"Id":3,
"FirstName":"e",
"LastName":"f"
},
{
"Id":4,
"FirstName":"g",
"LastName":"h"
}
]
}
]
But I need this result:
[
{
"Id":1,
"Employess":[
{
"Id":1
},
{
"Id":2
}
]
},
{
"Id":2,
"Employess":[
{
"Id":3
},
{
"Id":4
}
]
}
]
Do you have any ideas how to do that?

One method to get the result to be the format you want is along the lines of
var obj = offices.Select(p => new {Id = p.Id, Employess = p.Employess.Select(y=> new {y.Id})}).ToList();
ends up as
[{"Id":1,"Employess":[{"Id":1},{"Id":2}]},{"Id":2,"Employess":[{"Id":3},{"Id":4}]}]

You need a second Select that only selects the Employee Id.
var obj = offices.Select(o => new {Id = o.Id, Employess = o.Employess.Select(e => new { Id = e.Id })});

alter your line
var obj = offices.Select(p => new {Id = p.Id, Employess = p.Employess}).ToList();
to
var obj = offices.Select(p => new {Id = p.Id, Employess = p.Employess.Select(x=>new{Id=x.Id})}).ToList();

To have the expected result just replace:
Employess = p.Employess
With
Employess = p.Employess.Select(e => new { e.Id })
Finally you have this LINQ statement:
var obj = offices.Select(p => new {Id = p.Id, Employess = p.Employess.Select(e => new { e.Id })}).ToList();

Telerik MVC Chart not Rendering Data

I am creating a dashboard comprised of several Telerik UI for ASP.NET MVC Charts. The first graph is supposed to plot sales volume month by month for a given agent. My controller class is as follows:
static List<SalesAgentViewModel> SalesAgentData = new List<SalesAgentViewModel>(){
new SalesAgentViewModel
{
SalesAgentID = 1,
ChartData = new List<SalesAgentChartItem>()
{
new SalesAgentChartItem
{
MonthName="January",
MerchantMCVolume=25000,
MerchantVisaVolume=500000
},
new SalesAgentChartItem
{
MonthName="February",
MerchantMCVolume = 225000,
MerchantVisaVolume = 725000
},
new SalesAgentChartItem
{
MonthName="March",
MerchantMCVolume = 75000,
MerchantVisaVolume = 150250
}
}
},
new SalesAgentViewModel
{
SalesAgentID = 2,
ChartData = new List<SalesAgentChartItem>()
{
new SalesAgentChartItem
{
MonthName="January",
MerchantMCVolume = 98000,
MerchantVisaVolume = 75250
},
new SalesAgentChartItem
{
MonthName = "February",
MerchantMCVolume = 87500,
MerchantVisaVolume = 68250
},
new SalesAgentChartItem
{
MonthName = "March",
MerchantMCVolume = 68500,
MerchantVisaVolume = 78125
}
}
}
};
[Authorize(Roles ="Admin,SalesAgent")]
public ActionResult ReadSalesAgentData([DataSourceRequest]DataSourceRequest request)
{
return Json(SalesAgentData.ToDataSourceResult(request));
}
[Authorize(Roles ="Admin,SalesAgent")]
public ActionResult ReadGraphData(int id)
{
return Json(SalesAgentData.First(v => v.SalesAgentID == id).ChartData);
}
I then new up a chart in my view as follows:
<div class="container" id="dashboard">
#(Html.Kendo().Chart<SalesAgentChartItem>()
.Name("SalesAgentVolume")
.Title("Sales Agent Volume")
.DataSource(dataSource => dataSource
.Read(read => read.Action("ReadGraphData","SalesAgents"))
)
.Series(series=>
{
series.Line(s => s.MerchantMCVolume).CategoryField("Mastercard Volume");
series.Line(s => s.MerchantVisaVolume).CategoryField("Visa Volume");
})
.CategoryAxis(axis=>axis
.Categories(model=>model.MonthName))
)
</div>
When I run the application, the graph is rendered but an HTTP 500 is thrown stating:
System.ArgumentException: The parameters dictionary contains a null entry
for parameter 'id' of non-nullable type 'System.Int32' for method
'System.Web.Mvc.ActionResult ReadGraphData(Int32)' in
'Web.Controllers.SalesAgentsController'. An optional parameter must be a
reference type, a nullable type, or be declared as an optional parameter.
Parameter name: parameters
My intent is to show the volume for a given agent identified by SalesAgentID. How would I accomplish this?

Proper way to Categorize by a Property

I have made a C# LINQ query that categorizes (or groups) by a property and I am almost sure there is a better way. My project is full of these queries so I am really interested on how to achieve this the proper way.
This is how my query look like:
var g = _repository.GetEmployees();
var result =
g.GroupBy(x => x.City, (key, group) => group.First())
.Select(x => new {
city = x.City,
employees = g
.Where(y=>y.EmployeeID == x.EmployeeID)
.Select(y=> new {
fullname = y.FirstName + " " + y.LastName,
title = y.Title
})
.OrderBy(y=>y.fullname)
})
.OrderBy(x => x.city);
Sample of JSON output:
[
{
"city":"Barcelona",
"employees":[
{
"fullname":"Foo Bar",
"title":"Help Desk Technician"
},
{
"fullname":"Lorem Ipsum",
"title":"Information Technology Director"
}
]
},
{
"city":"London",
"employees":[
{
"fullname":"Le Query",
"title":"Information Technology Manager"
},
{
"fullname":"Please Help",
"title":"Management Information Systems Director"
}
]
}
]
The result is fine. What is the best way to achieve it?

It sounds like you just want:
var result = g.GroupBy(x => x.City, (key, group) => new {
city = key,
employees = group.Select(emp => new {
fullname = emp.FirstName + " " + emp.LastName,
title = emp.Title
})
});
In other words, you're just providing a projection for each group, which is "an anonymous type with the city, and all the employees for that city".