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Best way to find values not in two lists c#

I have two lists which I need to compare (carOptions and custOptions).
Both of these lists are in my Customer class like below:
public class CustomerDTO
{
public int CustomerId { get; set; }
//other props removed for brevity
public List<OptionDTO> SelectedCarOptions { get; set; }
public List<OptionDTO> SelectedCustomerOptions { get; set; }
}
var existingData = _myRepository.GetDataByCustomer(customerId, year);
var existingCarOptions = existingData.Select(f => f.SelectedCarOptions);
var existingCustomerOptions = existingData.Select(f => f.SelectedCustomerOptions);
existingData is an IEnumerable of CustomerDTO and then existingCarOptions and existingCustomerOptions is an IEnumerable<List<OptionDTO>>
In the method, I have a list of IEnumerable<OptionDTO> options that gets passed in. I then break this down into car or customer based on the Enum as below:
var newCarOptions = options.Where(o => o.OptionTypeID == OptionType.CarOptions);
var newCustomerOptions = options.Where(o => o.OptionTypeID == OptionType.CustomerOptions).ToList();
What I need to do is find which options are in one collection but no in the other.
I tried as below but getting an Error on the Except (I maybe need to create my own static method in that class) but I am not sure this is the best approach really?
if (existingCarOptions.Count() != newCarOptions.Count())
{
//var test = newCarOptions.Except(existingCarOptions);
}
if (existingCustomerOptions.Count() != newCustomerOptions.Count())
{
//var test2 = newCustomerOptions.Except(existingCustomerOptions);
}
Is it also quite a bit of code in the method - I could split it out into sperate methods if required but perhaps there is a simpler way I could achieve this?

I'm assuming OptionDTO has a property called Id, which uniquely identifies an option (you have to change the code accordingly if this is not the case), you may use HashSets to quickly find unmatched OptionsDTOs, while keeping the overall time cost O(n) (where n is the max number of combined options).
Create the existing options sets:
var existingCarOptions = existingData.SelectMany(d => d.SelectedCarOptions).Select(o => o.Id);
var existingCustomerOptions = existingData.SelectMany(d => d.SelectedCustomerOptions).Select(o => o.Id);
var existingCarOptionsIds = new HashSet<int>(existingCarOptions);
var existingCustomerOptionsIds = new HashSet<int>(existingCustomerOptions );
Then you extract options missing in existing sets with:
var unmatchedCarOptions = newCarOptions.Where(o => !existingCarOptionsIds.Contains(o.Id));
var unmatchedCustomerOptions = newCustomerOptions.Where(o => !existingCustomerOptionsIds.Contains(o.Id));

If you want to compare two classes you can use IEqualityComparer
public class OptionComparer : IEqualityComparer<OptionDTO>
{
public bool Equals(OptionDTO x, OptionDTO y)
{
if (object.ReferenceEquals(x, y))
{
return true;
}
if (object.ReferenceEquals(x, null) ||
object.ReferenceEquals(y, null))
{
return false;
}
return x.OptionTypeID == y.OptionTypeID ;
}
public int GetHashCode(OptionDTO obj)
{
if (obj == null)
{
return 0;
}
return obj.OptionTypeID.GetHashCode();
}
With using this you can ıdentify that What is the concept of equality for these classes.
Now we can find different values..
public List<OptionDTO>CalculateDiffBetweenLists(List<OptionDTO> left, List<OptionDTO> right){
List<OptionDTO> optionDiff;
optionDiff = left.Except(right, new OptionComparer ()).ToList();
return optionDiff ;
}

linq query group by fail to group all rows with similar keys

this is my query:
rows.GroupBy(row => new TaxGroupObject
{
EnvelopeID = row.Field<int>("EnvelopeID"),
PolicyNumber = row.Field<string>("PolicyNumber"),
TZ = row.Field<string>("TZ")
})
.Select(row =>
{
int i;
if (row.Key.EnvelopeID == 5713 && row.Key.PolicyNumber == "50002617" && row.Key.TZ == "50002617")
i=1+1;
var newRow = structure.NewRow();
newRow["PolicyNumber"]=row.Key.PolicyNumber;
newRow["TZ"]=row.Key.TZ;
newRow["CreditPremiaTaxParagraph45"] = row.Sum(x => decimal.Parse(x["CreditPremiaTaxParagraph45"].ToString()));
newRow["WorklossTax"] = row.Sum(x => decimal.Parse(x["WorklossTax"].ToString()));
newRow["MiscTax"] = row.Sum(x => decimal.Parse(x["MiscTax"].ToString()));
newRow["EnvelopeID"] = row.Key.EnvelopeID;
return newRow;
}
);
internal class TaxGroupObject
{
public long? EnvelopeID{ get; set; }
public string PolicyNumber { get; set; }
public string TZ { get; set; }
}
i put a breakpoint on the line with "i=1+1", after an if condition comparing all the keys i've used for the group by with some hard coded values. that break point is being hit twice, although the group by suppose to group all rows with same keys together. the thing is that for most of the values in the table the grouping works just fine and i cant understand how its possible. if you can help in any way it would be highly appreciated.

The problem is that TaxGroupObject does not implement GetHashCode and Equals. These methods are used by GroupBy to determine what makes one TaxGroupObject object equal to another. By default, it's by reference equality, not property equality.
This should work, using the GetHashCode algorithm from What is the best algorithm for an overridden System.Object.GetHashCode?:
internal class TaxGroupObject
{
public long? EnvelopeID { get; set; }
public string PolicyNumber { get; set; }
public string TZ { get; set; }
public override int GetHashCode()
{
unchecked // Overflow is fine, just wrap
{
int hash = 17;
hash = hash * 23 + EnvelopeID.GetHashCode();
hash = hash * 23 + (PolicyNumber != null ? PolicyNumber.GetHashCode() : -2);
hash = hash * 23 + (TZ != null ? TZ.GetHashCode() : -1);
return hash;
}
}
public override bool Equals(object obj)
{
if (obj.GetType() != typeof(TaxGroupObject))
return false;
var other = (TaxGroupObject)obj;
return this.EnvelopeID == other.EnvelopeID &&
this.PolicyNumber == other.PolicyNumber &&
this.TZ == other.TZ;
}
}
Also, you should only use immutable objects in something like a grouping or dictionary. At a minimum, you must be sure that the objects here do not change during your grouping.

eventually i found it simpler to give up inheritance and use a struct instead of class, it also works since struct is a value type therefore doesn't need equals method override. I am intrested in which of these approaches bring better performance, if anybody knows. Intuitively it seems like structs are more efficient, but I am not sure, and I currently don't have the time to emulate the two options or make the proper re(google)search.
Thanks

Loading the Table little by little in chunks

To not run out of memory by brining in the whole table at ones, I am doing in it chunks of LOAD_SIZE records.
Here is how I am doing it, I feel like there are some indexes that are off by one record? and possible performance improvements that I can do in
So I wanted to have your opinion on this approach.
int totalCount = repo.Context.Employees.Count();
int startRow = 0;
while (startRow <= totalCount)
{
repo.PaginateEmployees(startRow, LOAD_SIZE);
startRow = startRow + LOAD_SIZE ;
}
public List<EmpsSummary> PaginateEmployees(int startRow, int loadSize)
{
var query = (from p in this.Context.Employees
.Skip(startRow).Take(loadSize)
select new EmpsSummary
{
FirstName = p.FirstName,
LastName = p.LastName,
Phone = p.Phone
});
return query.ToList();
}

Because of how Linq works (lazy loading and has compares), if you formulate your statements right it will manage memory much better than you will be able.
From your comments (which should be added to the question) I offer this solution which should manage memory for you just fine.
This example code is not intended to compile -- it is given as an example
// insert list
List<EmpsSummary> insertList;
// add stuff to insertList
List<EmpsSummary> filteredList = insertList.Except(this.Context.Employees);
This assumes that this.Context.Employees is of type EmpsSummary. If it isn't you have to cast it to the correct type.
Also you will need to be able to compare EmpsSummary. To do so create this IEquitable like this:
This example code is not intended to compile -- it is given as an example
public class EmpsSummary : IEquatable<EmpsSummary>
{
public string FirstName { get; set; }
public string LastName { get; set; }
public string Phone { get; set; }
public bool Equals(EmpsSummary other)
{
//Check whether the compared object is null.
if (Object.ReferenceEquals(other, null)) return false;
//Check whether the compared object references the same data.
if (Object.ReferenceEquals(this, other)) return true;
//Check whether the products' properties are equal.
return FirstName.Equals(other.FirstName) &&
LastName.Equals(other.LastName) &&
Phone.Equals(other.Phone);
}
// If Equals() returns true for a pair of objects
// then GetHashCode() must return the same value for these objects.
public override int GetHashCode()
{
int hashProductFirstName = FirstName == null ? 0 : FirstName.GetHashCode();
int hashProductLastName = LastName == null ? 0 : LastName.GetHashCode();
int hashProductPhone = Phone == null ? 0 : Phone.GetHashCode();
//Calculate the hash code
return hashProductFirstName ^ hashProductLastName ^ hashProductPhone;
}
}

How to manage multiple classes in C#? (Duplication) [closed]

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Simple question. I am writing an application in VS 2010 C# for fun (Learning experience) and I don't know how to get around a problem in an acceptable way.
Lets say I have a class called "Biscuit"
class Biscuit
{
private string Brand = String.Empty;
private string Variant = String.Empty;
public void CreateBiscuit(string pBrand, string pVariant)
{
Brand = pBrand;
Variant = pVariant;
}
public void GetDetails(ref string pBrand, ref string pVariant)
{
pBrand = Brand;
pVariant = Variant;
}
}
The user can create as many instances of this object as they want. All they have to do is give a brand and variant. I then create the object and store it in a list
Problem is, I don't want there to be duplicates. So no two objects where both the Brand and Variant are the same as another instance .
I could loop through all objects in the BiscuitLibrary, but this doesn't seem like good practice, or good performance. (Current Code Below)
List<Biscuit> BiscuitLibrary = new List<Biscuit>();
public void CheckDuplicate(string pBrand, string pVariant)
{
string ObjectBrand = String.Empty
string ObjectVariant = String.Empty;
foreach (Biscuit CurrentItem in BiscuitLibrary)
{
CurrentItem.GetDetails(ref ObjectBrand, ref ObjectVariant);
if ((ObjectBrand == pBrand) && (ObjectVariant == pVariant))
{
MessageBox.Show("This Biscuit Already Exists, Sorry!");
}
else
{
Biscuit NewBiscuit = new Biscuit();
NewBiscuit.CreateBiscuit(pBrand, pVariant);
BiscuitLibrary.Add(NewBiscuit);
}
}
}
How should I do this?
Thanks, Tom!

Probably the best practice would be to store all instances in a HashSet instead of a List. This would be especially useful for performance if you planned to store thousands of instances. Going through each of them in a List and checking for duplicates would be an expensive operation. While HashSet organizes its contents based on object hash codes in a way that allows very efficient duplicate checks. You can read more about HashSet here:
http://msdn.microsoft.com/en-us/library/bb397727(v=vs.110).aspx
Before HashSet can be used, you have to prepare your class by overriding its GetHashCode() and Equals() methods:
class Biscuit
{
public string Brand { get; set; }
public string Variant { get; set; }
public Biscuit(string brand, string variant)
{
Brand = brand;
Variant = variant;
}
public override bool Equals(object obj)
{
if (obj == null || typeof(Biscuit) != obj.GetType())
return false;
Biscuit biscuitObj = obj as Biscuit;
return biscuitObj.Brand == this.Brand && biscuitObj.Variant == this.Variant;
}
public override int GetHashCode()
{
unchecked
{
int hash = 17;
hash = hash * 23 + this.Brand.GetHashCode();
hash = hash * 23 + this.Variant.GetHashCode();
return hash;
}
}
}
Now you can use this class with a HashSet:
//we create a HashSet and add 4 biscuits to it
//one of the biscuits is duplicate and will not be inserted
var uniqueBiscuitBox = new HashSet<Bisquit>();
uniqueBiscuitBox.Add(new Biscuit("A", "1"));
uniqueBiscuitBox.Add(new Biscuit("A", "1"));
uniqueBiscuitBox.Add(new Biscuit("B", "1"));
uniqueBiscuitBox.Add(new Biscuit("C", "4"));
Console.WriteLine(uniqueBiscuitBox.Count()); //returns 3

As you already using something similar to a Factory pattern you could do some modifications of your code tom make it work as you want to:
class Biscuit
{
// You should use properties
public string Brand {get; private set;}
public string Variant {get; private set;}
// Use a protected constructor so it can't be used outside the class
protected Biscuit(string brand, string variant)
{
Brand = brand;
Variant = variant;
}
// Use a static list to hold the already crated biscuits
private static List<Biscuit> _existingBiscuits = new List<Biscuit>();
// "Factory method" to create Biscuit instances
public static Biscuit CreateBiscuit(string pBrand, string pVariant)
{
// Use LINQ to find if there are any biscuits already crated with the brand and variant
if (_existingBiscuits.Any(b => b.Brand == pBrand && b.Variant == pVariant))
{
// If the biscuit already exist return null, no biscuit created
return null;
}
else
{
// Create biscuit and add it to the list
var biscuit = new Biscuit(pBrand, pVariant);
_existingBiscuits.Add(biscuit);
return biscuit;
}
}
}

First suggestion: require instances be constructed with valid data; throw if the user tries to pass invalid data and avoid the “construct then initialize” antipattern.
public class Biscuit : IEquatable<Biscuit>
{
public string Brand { get; private set; }
public string Variant { get; private set; }
public Biscuit(string brand, string variant)
{
if (brand == null) throw new ArgumentNullException("brand");
if (variant == null) throw new ArgumentNullException("variant");
Brand = brand;
Variant = variant;
}
public bool Equals(Biscuit b)
{
if (b == null) return false;
return string.Equals(Brand, b.Brand, StringComparison.InvariantCulture)
&& string.Equals(Variant, b.Variant, StringComparison.InvariantCulture);
}
}
If you want a list with special rules (e.g. no two items have the same Brand and Variant) then create a class that implements the rules. Do not use generic lists and try to enforce rules at runtime.
Copying #SoftwareFactor's idea, you can create strongly-typed HashSets with an IEqualityComparer:
class BiscuitEqualityComparer : IEqualityComparer<Biscuit>
{
public bool Equals(Biscuit b1, Biscuit b2)
{
if (b1 == null) return b2 == null;
return b1.Equals(b2);
}
public int GetHashCode(Biscuit b)
{
if (b == null) throw new ArgumentNullException("b");
return b.Brand.GetHashCode() ^ b.Variant.GetHashCode();
}
}
var bh = new HashSet<Biscuit>(new BiscuitEqualityComparer());
bh.Add(new Biscuit("Alpha", "Beta"));
bh.Add(new Biscuit("Alpha", "Gamma"));
bh.Add(new Biscuit("Alpha", "Beta")); // will not be added.

MSTest: CollectionAssert.AreEquivalent failed. The expected collection contains 1 occurrence(s) of

Question:
Can anyone tell me why my unit test is failing with this error message?
CollectionAssert.AreEquivalent failed. The expected collection contains 1
occurrence(s) of . The actual
collection contains 0 occurrence(s).
Goal:
I'd like to check if two lists are identical. They are identical if both contain the same elements with the same property values. The order is irrelevant.
Code example:
This is the code which produces the error. list1 and list2 are identical, i.e. a copy-paste of each other.
[TestMethod]
public void TestListOfT()
{
var list1 = new List<MyPerson>()
{
new MyPerson()
{
Name = "A",
Age = 20
},
new MyPerson()
{
Name = "B",
Age = 30
}
};
var list2 = new List<MyPerson>()
{
new MyPerson()
{
Name = "A",
Age = 20
},
new MyPerson()
{
Name = "B",
Age = 30
}
};
CollectionAssert.AreEquivalent(list1.ToList(), list2.ToList());
}
public class MyPerson
{
public string Name { get; set; }
public int Age { get; set; }
}
I've also tried this line (source)
CollectionAssert.AreEquivalent(list1.ToList(), list2.ToList());
and this line (source)
CollectionAssert.AreEquivalent(list1.ToArray(), list2.ToArray());
P.S.
Related Stack Overflow questions:
I've seen both these questions, but the answers didn't help.
CollectionAssert use with generics?
Unit-testing IList with CollectionAssert

You are absolutely right. Unless you provide something like an IEqualityComparer<MyPerson> or implement MyPerson.Equals(), the two MyPerson objects will be compared with object.Equals, just like any other object. Since the objects are different, the Assert will fail.

It works if I add an IEqualityComparer<T> as described on MSDN and if I use Enumerable.SequenceEqual. Note however, that now the order of the elements is relevant.
In the unit test
//CollectionAssert.AreEquivalent(list1, list2); // Does not work
Assert.IsTrue(list1.SequenceEqual(list2, new MyPersonEqualityComparer())); // Works
IEqualityComparer
public class MyPersonEqualityComparer : IEqualityComparer<MyPerson>
{
public bool Equals(MyPerson x, MyPerson y)
{
if (object.ReferenceEquals(x, y)) return true;
if (object.ReferenceEquals(x, null) || object.ReferenceEquals(y, null)) return false;
return x.Name == y.Name && x.Age == y.Age;
}
public int GetHashCode(MyPerson obj)
{
if (object.ReferenceEquals(obj, null)) return 0;
int hashCodeName = obj.Name == null ? 0 : obj.Name.GetHashCode();
int hasCodeAge = obj.Age.GetHashCode();
return hashCodeName ^ hasCodeAge;
}
}

I was getting this same error when testing a collection persisted by nHibernate. I was able to get this to work by overriding both the Equals and GetHashCode methods. If I didn't override both I still got the same error you mentioned:
CollectionAssert.AreEquivalent failed. The expected collection contains 1 occurrence(s) of .
The actual collection contains 0 occurrence(s).
I had the following object:
public class EVProjectLedger
{
public virtual long Id { get; protected set; }
public virtual string ProjId { get; set; }
public virtual string Ledger { get; set; }
public virtual AccountRule AccountRule { get; set; }
public virtual int AccountLength { get; set; }
public virtual string AccountSubstrMethod { get; set; }
private Iesi.Collections.Generic.ISet<Contract> myContracts = new HashedSet<Contract>();
public virtual Iesi.Collections.Generic.ISet<Contract> Contracts
{
get { return myContracts; }
set { myContracts = value; }
}
public override bool Equals(object obj)
{
EVProjectLedger evProjectLedger = (EVProjectLedger)obj;
return ProjId == evProjectLedger.ProjId && Ledger == evProjectLedger.Ledger;
}
public override int GetHashCode()
{
return new { ProjId, Ledger }.GetHashCode();
}
}
Which I tested using the following:
using (ITransaction tx = session.BeginTransaction())
{
var evProject = session.Get<EVProject>("C0G");
CollectionAssert.AreEquivalent(TestData._evProjectLedgers.ToList(), evProject.EVProjectLedgers.ToList());
tx.Commit();
}
I'm using nHibernate which encourages overriding these methods anyways. The one drawback I can see is that my Equals method is based on the business key of the object and therefore tests equality using the business key and no other fields. You could override Equals however you want but beware of equality pollution mentioned in this post:
CollectionAssert.AreEquivalent failing... can't figure out why

If you would like to achieve this without having to write an equality comaparer, there is a unit testing library that you can use, called FluentAssertions,
https://fluentassertions.com/documentation/
It has many built in equality extension functions including ones for the Collections. You can install it through Nuget and its really easy to use.
Taking the example in the question above all you have to write in the end is
list1.Should().BeEquivalentTo(list2);
By default, the order matters in the two collections, however it can be changed as well.

I wrote this to test collections where the order is not important:
public static bool AreCollectionsEquivalent<T>(ICollection<T> collectionA, ICollection<T> collectionB, IEqualityComparer<T> comparer)
{
if (collectionA.Count != collectionB.Count)
return false;
foreach (var a in collectionA)
{
if (!collectionB.Any(b => comparer.Equals(a, b)))
return false;
}
return true;
}
Not as elegant as using SequenceEquals, but it works.
Of course to use it you simply do:
Assert.IsTrue(AreCollectionsEquivalent<MyType>(collectionA, collectionB, comparer));