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I hope everyone is well.
I have some practice code here that I've been working on and the code works and I have no issues with it however, I don't find that I fully understand what I've written and why it works.
I want to try and be able to understand my work so that I can become a better programmer, I've left comments for the code that I dont fully understand, the rest I am comfortable with.
I would appreciate any one with the spare time to give me a few pointers and some help, thank you very much.
namespace GenericList
{
class Program
{
static void Main(string[] args)
{
/* I understand how objects work, but I dont fully understand
what is happening when I am passig through my constructer
name through the List */
List<Cities> cities = new List<Cities>();
/* I am passing matching arguments through each instance
of my cities List object but I still struggle to
visualise this process */
cities.Add(new Cities(1, "Durban - Home to the largest harbor in Africa"));
cities.Add(new Cities(2, "Johannesburg - The largest city in the country"));
cities.Add(new Cities(3, "Gqebetha - Also known as P.E, the friendly city"));
cities.Add(new Cities(4, "Bloemfontien - Host of the Rose Festival"));
cities.Add(new Cities(5, "Pretoria - South Africa's capital"));
Console.WriteLine("Which city would you like to know an interesting fact for?" +
"\n1) Durban" +
"\n2) Johannesburg" +
"\n3) Gqebetha" +
"\n4) Bloemfontien" +
"\n5) Pretoria" +
"\nEnter the number for the city you want:");
int answer = int.Parse(Console.ReadLine());
bool found = false;
for (int i = 0; i < cities.Count; i++)
{
if (cities[i].Id.Equals(answer))
{
Console.WriteLine("\nANSWER: " + cities[i].City);
found = true;
}
}
if (!found)
{
Console.WriteLine("\nWe couldn't find what you are looking for.");
}
}
}
class Cities
{
int id;
string city;
public Cities(int id, string city)
{
this.id = id;
this.city = city;
}
public int Id { get => id; set => id = value; }
public string City { get => city; set => city = value; }
}
}
List<Cities> cities = new List<Cities>();
Here you are creating a List, which contains only the object of Cities's class.
List is a array type data structure with various utilities(method).
Here you are using Add(), which append a new object to the list (in that case only Cities object as you declare in first line List<Cities>).
cities.Add(new Cities(1, "Durban - Home to the largest harbor in Africa"));
If I break down this line this will be:
// Creating a new Cities object
var newCity = new Cities(1, "Durban - Home to the largest harbor in Africa");
cities.Add(newCity );
Last line from the code block is appending newCity to the list of cities
Hope you understand now, If anything left unclear let me know
i rewrote with linq so you can see as a different approach. more easy reading code
void Main()
{
List<Cities> cities = new List<Cities>();
//add to cities array a new City class, since constructor accept 2 parameters you supply them on new object creation
Cities city;
city = new Cities(1, "Durban - Home to the largest harbor in Africa");
cities.Add(city);
city = new Cities(2, "Johannesburg - The largest city in the country");
cities.Add(city);
city = new Cities(3, "Gqebetha - Also known as P.E, the friendly city");
cities.Add(city);
city = new Cities(4, "Bloemfontien - Host of the Rose Festival");
cities.Add(city);
city = new Cities(5, "Pretoria - South Africa's capital");
cities.Add(city);
//different approach: create list with objects
cities = new List<Cities>()
{
new Cities(1, "Durban - Home to the largest harbor in Africa"),
new Cities(2, "Johannesburg - The largest city in the country"),
new Cities(3, "Gqebetha - Also known as P.E, the friendly city"),
new Cities(4, "Bloemfontien - Host of the Rose Festival"),
new Cities(5, "Pretoria - South Africa's capital")
};
Console.WriteLine("Which city would you like to know an interesting fact for?" +
"\n1) Durban" +
"\n2) Johannesburg" +
"\n3) Gqebetha" +
"\n4) Bloemfontien" +
"\n5) Pretoria" +
"\nEnter the number for the city you want:");
int answer = int.Parse(Console.ReadLine());
var result = cities
.Select((obj, index) => new { index, obj }) //set index for each object
.Where(w => w.index == answer)
.FirstOrDefault();
if (result == null)
Console.WriteLine("\nWe couldn't find what you are looking for.");
else
Console.WriteLine("\nANSWER: " + result.obj.City);
}
class Cities
{
//class properties
public int Id { get; set; }
public string City { get; set; }
//Parameterized Constructor https://www.tutlane.com/tutorial/csharp/csharp-constructors-with-examples#divcspzcst
public Cities(int id, string city)
{
Id = id;
City = city;
}
}
With
List<Cities> cities = new List<Cities>();
you create a new List-object that can store Cities objects. The generic type parameter <Cities> denotes the type of the list items and does not refer to the constructor. As an example, the following code would create a list that could store integer values:
List<int> lst = new List<int>();
The List<T> class is a generic type. The basic operations for a list like adding, removing, enumerating and so on are the same no matter what the type of the list items is. By creating a generic type, you can implement the functionality without knowing which types are used later on when you create an object. You might compare this to a method: when you implement the method, you define the parameters and their types; when you call the method, you supply the values of the parameters.
The code in the following line performs two tasks:
cities.Add(new Cities(1, "Durban - Home to the largest harbor in Africa"));
First, a new object of type Cities is created and initialized through the constructor. Second, it is added to the list. These are two separate steps that can also written like this:
// Create new object of type Cities
var city = new Cities(1, "Durban - Home to the largest harbor in Africa");
// Add newly created object to list
cities.Add(city);
As #BinRohan suggested in the comments, it might be a good idea the rename the Cities class to City because it defines a single city, not a collection of cities.
When you write this line of code
List<Cities> cities = new List<Cities>();
You instantiate an object being a List of "Cities". List is a "generic" type. It means it is able to handle any type and will behave the same. You could have a List or List, you'll manipulate different objects but the behaviour of List remains the same. You are not "passing" Cities to the List constructor, consider List as a type in itself.
It would be equivalent of declaring an array of Cities for example. There is no data in your list yet but it is ready to receive multiple instance of Cities.
Then when you write
cities.Add(New Cities{prop1=value,prop2=value...});
at run time it will do something like
var c = new Cities();
c.prop1=value;
c.prop2=value;
cities.Add(c);
It's kind of a shortcut which also make the code more readable.
Related
I have three lists, two object lists to be compared based on the third list which is of type string and the resultant should be the common values from both the lists.
Example
List<Object1>
- Name
- ID
- AddressList[]
AddressList Item
- State
- City
- Zip
AddressList Item
- State
- City
- Zip
List<Object1>
- Name
- ID
- AddressList[]
AddressList Item
- State
- City
- Zip
AddressList Item
- State
- City
- Zip
List<string> = new List<string> {"State","City"};
In this case only the values of State and City must be compared. If the List= new List {"State"} then only the State values from both the list objects needs to be compared.
I've been trying to find a way to do this by myself but I feel like everything I did is completely wrong. I'd be more than happy if someone could help me. Thanks a lot!
There are some open source libraries that provide that kind of functionality, such as ObjectComparer: https://github.com/ValeraT1982/ObjectsComparer
It allows you to compary variable number of properties such as this:
//Initialize objects and comparer
var a1 = new ClassA { StringProperty = "String", IntProperty = 1 };
var a2 = new ClassA { StringProperty = "String", IntProperty = 1 };
var comparer = new Comparer<ClassA>();
//Compare objects
IEnumerable<Difference> differences;
var isEqual = comparer.Compare(a1, a2, out differences);
//Print results
Debug.WriteLine(isEqual ? "Objects are equal" : string.Join(Environment.NewLine, differenses));
Without using a third party library, you would need to use reflection to compare them dynamically like that.
Something like this(missing all kinds of safety code):
var propertyInfo = typeof(Object1).GetProperty(propName);
object valueA;
object valueB;
valueA = propertyInfo.GetValue(objectA, null);
valueB = propertyInfo.GetValue(objectB, null);
I'm programming in C# and I want to instantiate lots of new objects to my application, all of the same type, but with different values for their properties. Example:
Student student1 = new Student();
student1.Name = "James";
student1.Age = 19;
student1.City = "Los Angeles";
Student student2 = new Student();
student2.Name = "Karen";
student2.Age = 20;
student2.City = "San Diego";
Student student3 = new Student();
student3.Name = "Bob";
student3.Age = 20;
student3.City = "Dallas";
This way of coding seems really wrong to me because what if I didn't need 3, but 500 students? What would be the best way to do it then?
I tried to use a for loop for this but that doesn't work because the property values differ.
What is the most efficient way to do this?
Thanks in advance.
In order to do anything with your objects at runtime you will probably want them in a list.
Without reading from a file or database, etc., the most concise way might be :
var Students = new List<Student>{
new Student { Name = "Bob", Age = 22, City = "Denver" },
new Student { Name = "Sally", Age = 33, City = "Boston" },
new Student { Name = "Alice", Age = 12, City = "Columbus" }
};
I don't know your end goal however, is this just mock data, like for a test?
Add constructor to Student like this
Student (string name, int age, string city)
{
Name = name;
Age = age;
City = city;
}
///
Student student1 = new Student("James", 19, "Los Angeles");
Well, if what you mean by more efficient way to do it is just to write less code, you could instanciate them assigning the property's values at once, just like:
Student student1 = new Student() { Name = "James", Age = 19, City = "Los Angeles" };
If you want not just to write less code, but to - let's say - read the data from another source (like a Json list, or a TXT file) you will have to write a loader for it.
Well, it depends what you are going to use it for. If it’s for testing, then you could use a custom built tool to create random Students:
public class RandomStudentCreator
{
private readonly Random rnd = new Random();
private readonly IList<string> cities, names;
private readonly int minAge, maxAge;
public RandomStudentCreator(
IList<string> names,
IList<string> cities,
int minimumInckusiveAge,
int maximumExclusiveAge)
{
//Argument validation here
this.cities = cities;
this.names = names;
minAge = minimumInckusiveAge;
maxAge = maximumExclusiveAge;
}
public Student Next()
{
var student = new Student();
student.Name = names[rnd.Next(names.Count);
student.City = cities[rnd.Next(cities.Count);
Student.Age = rnd.Next(minAge, maxAge);
}
}
If this is production code, then you should be creating students based on:
User input
Some data backend (DB, text file, etc.)
But in any case, you don’t want to create a variable for each student. You probably want a collection of students. Depending on what you want to do with them, the type of collection you need may vary, the framework gives you plenty of options:
Arrays: Student[]
Lists: List<Student>
Queues: Queue<Student>
Stacks: Stack<Student>
Sets: HashSet<Student>
Etc.
And last but not least, you probably want to implement a constructor in Student that takes a name, city and age to make instantiation a little bit more compact than what you currently have:
public class Student
{
public Student(string name,
int age,
string city)
{
Name = name;
Age = age;
City = city;
}
//...
}
var john = new Student(“John”, 19, “LA”);
Programming is not about typing data. Need a lot of data? - Load them from files, databases, servers, through GUI, etc.
You can make a handy constructor, you can make factories and builders, but they are not for creating hundreds of objects in a row. Even if it is historical data, one day you will want to change them, fix something in them. Believe me, it's much easier to separate them from the code and store somewhere else, than to edit hundreds of lines of code later.
If you want 500 students I suggest extracting data to a file, database etc. student1..student499 implementation looks very ugly: let's organize them into array: Student[] students. As an example, let's use the simplest csv file Students.csv solution in the format
name,age,city
E.g.
name,age,city
James,19,Los Angeles
Karen,20,San Diego
Bob,20,Dallas
Having the file completed you can easily read it:
using System.IO;
using System.Linq;
...
Student[] students = File
.ReadLines("Students.csv")
.Where(line => !string.IsNullOrWhiteSpace(line)) // Skip empty lines
.Skip(1) // Skip header
.Select(line => line.Split(','))
.Select(items => new Student() {
Name = items[0],
Age = int.Parse(items[1]),
City = items[2], })
.ToArray();
Sorry for the incoherent title. I don't know how to concisely explain my problem, which is why I didn't really know how to look it up. I'll explain using an example...
Let's say I have a class:
public class cas
{
public string name { get; set; }
public int num { get; set; }
}
With that class, I make several objects and stick them into a list. For the sake of example, I will make 4:
var list = new List<cas>
{
new cas { name = "firstname", num = 1 },
new cas { name = "firstname", num = 2 },
new cas { name = "lastname", num = 3 },
new cas { name = "lastname", num = 4 }
};
Is there a way to take this List and combine any objects with the same name field?
So, the new list would be 1 object with:
name = "firstname", num = 3,
name = "lastname", num = 7
There's the obvious "long" way to do it, but it would be clunky and expensive (go through the list several times to find like-objects). I was wondering if I was missing any clean way of doing it. I intentionally made a simple example so that the answer would be a proof of concept rather than writing my code for me. My actual problem is more complex than this, but I can't figure out this one aspect of it.
Using Linq, you have a GroupBy Method and a Select Method:
list = list.GroupBy(x=> x.name)
.Select(x=> new cas() { name = x.Key, num = x.Sum(y=> y.num) }).ToList();
Or using Elegant query-syntax:
list = (from item in list
group item by item.name into grouping
select new cas()
{
name = grouping.Key,
num = grouping.Sum(x => x.num)
}).ToList();
Note that to use these methods, you have to add using System.Linq at the top of your source file.
You can use linq, you would have to group them on name property and then sum on the num property of each group like:
var result = list.GroupBy(x=>x.name)
.Select(g=> new cas
{
name = g.Key,
num = g.Sum(x=>x.num)
});
I am implementing a integration with NetSuite in C#. In the external system I need to populate a list of countries that will match NetSuite's country list.
The NetSuite Web Service provides an enumeration call Country
public enum Country {
_afghanistan,
_alandIslands,
_albania,
_algeria,
...
You can also get a list of country Name and Code (in an albeit not so straight forward way) from the web service. (See: http://suiteweekly.com/2015/07/netsuite-get-all-country-list/)
Which gives you access to values like this:
Afghanistan, AF
Aland Islands, AX
Albania, AL
Algeria, DZ
American Samoa, AS
...
But, as you can see, there is no way to link the two together. (I tried to match by index but that didn't work and sounds scary anyway)
NetSuite's "help" files have a list. But this is static and I really want a dynamic solution that updates as NetSuites updates because we know countries will change--even is not that often.
Screenshot of Country Enumerations from NetSuite help docs
The only solutions I have found online are people who have provided static data that maps the two sets of data. (ex. suiteweekly.com /2015/07/netsuite-complete-country-list-in-netsuite/)
I cannot (don't want to) believe that this is the only solution.
Anyone else have experience with this that has a better solution?
NetSuite, if you are reading, come on guys, give a programmer a break.
The best solution I have come up with is to leverage the apparent relationship between the country name and the enumeration key to forge a link between the two. I am sure others could improve on this solution but what I would really like to see is a solution that isn't a hack like this that relies on an apparent pattern but rather on that is based on an explicit connection. Or better yet NetSuite should just provide the data in one place all together.
For example you can see the apparent relationship here:
_alandIslands -> Aland Islands
With a little code I can try to forge a match.
I first get the Enumeration Keys into an array. And I create a list of objects of type NetSuiteCountry that will hold my results.
var countryEnumKeys = Enum.GetNames(typeof(Country));
var countries = new List<NetSuiteCountry>();
I then loop through the list of country Name and Code I got using the referenced code above (not shown here).
For each country name I then strip all non-word characters from the country name with Regex.Replace, prepend an underscore (_) and then convert the string to lowercase. Finally I try to find a match between the Enumeration Key (converted to lowercase as well) and the matcher string that was created. If a match is found I save all the data together the countries list.
UPDATE: Based on the comments I have added additional code/hacks to try to deal with the anomalies without hard-coding exceptions. Hopefully these updates will catch any future updates to the country list as well, but no promises. As of this writing it was able to handle all the known anomalies. In my case I needed to ignore Deprecated countries so those aren't included.
foreach (RecordRef baseRef in baseRefList)
{
var name = baseRef.name;
//Skip Deprecated countries
if (name.EndsWith("(Deprecated)")) continue;
//Use the name to try to find and enumkey match and only add a country if found.
var enumMatcher = $"_{Regex.Replace(name, #"\W", "").ToLower()}";
//Compares Ignoring Case and Diacritic characters
var enumMatch = CountryEnumKeys.FirstOrDefault(e => string.Compare(e, enumMatcher, CultureInfo.CurrentCulture, CompareOptions.IgnoreNonSpace | CompareOptions.IgnoreCase) == 0);
//Then try by Enum starts with Name but only one.
if (enumMatch == null)
{
var matches = CountryEnumKeys.Where(e => e.ToLower().StartsWith(enumMatcher));
if (matches.Count() == 1)
{
Debug.Write($"- Country Match Hack 1 : ");
enumMatch = matches.First();
}
}
//Then try by Name starts with Enum but only one.
if (enumMatch == null)
{
var matches = CountryEnumKeys.Where(e => enumMatcher.StartsWith(e.ToLower()));
if (matches.Count() == 1)
{
Debug.Write($"- Country Match Hack 2 : ");
enumMatch = matches.First();
}
}
//Finally try by first half Enum and Name match but again only one.
if (enumMatch == null)
{
var matches = CountryEnumKeys.Where(e => e.ToLower().StartsWith(enumMatcher.Substring(0, (enumMatcher.Length/2))));
if (matches.Count() == 1)
{
Debug.Write($"- Country Match Hack 3 : ");
enumMatch = matches.First();
}
}
if (enumMatch != null)
{
var enumIndex = Array.IndexOf(CountryEnumKeys, enumMatch);
if (enumIndex >= 0)
{
var country = (Country) enumIndex;
var nsCountry = new NetSuiteCountry
{
Name = baseRef.name,
Code = baseRef.internalId,
EnumKey = country.ToString(),
Country = country
};
Debug.WriteLine($"[{nsCountry.Name}] as [{nsCountry.EnumKey}]");
countries.Add(nsCountry);
}
}
else
{
Debug.WriteLine($"Could not find Country match for: [{name}] as [{enumMatcher}]");
}
}
Here is my NetSuiteCountry class:
public class NetSuiteCountry
{
public string Name { get; set; }
public string Code { get; set; }
public string EnumKey { get; set; }
public Country Country { get; set; }
}
Let me start off with a disclaimer that I'm not a coder, and this is the first day I've tried to look at a C# program.
I need something similar for a Javascript project where I need the complete list of Netsuite company names, codes and their numeric values and when reading the help it seemed like the only way was through webservices.
I downloaded the sample application for webservices from Netsuite and a version of Visual Studio and I was able to edit the sample program provided to create a list of all of the country names and country codes (ex. Canada, CA).
I started out doing something similar to the previous poster to get the list of country names:
string[] countryList = Enum.GetNames(typeof(Country));
foreach (string s in countryList)
{
_out.writeLn(s);
}
But I later got rid of this and started a new technique. I created a class similar to the previous answer:
public class NS_Country
{
public string countryCode { get; set; }
public string countryName { get; set; }
public string countryEnum { get; set; }
public string countryNumericID { get; set; }
}
Here is the new code for getting the list of company names, codes and IDs. I realize that it's not very efficient as I mentioned before I'm not really a coder and this is my first attempt with C#, lots of Google and cutting/pasting ;D.
_out.writeLn(" Attempting to get Country list.");
// Create a list for the NS_Country objects
List<NS_Country> CountryList = new List<NS_Country>();
// Create a new GetSelectValueFieldDescription object to use in a getSelectValue search
GetSelectValueFieldDescription countryDesc = new GetSelectValueFieldDescription();
countryDesc.recordType = RecordType.customer;
countryDesc.recordTypeSpecified = true;
countryDesc.sublist = "addressbooklist";
countryDesc.field = "country";
// Create a GetSelectValueResult object to hold the results of the search
GetSelectValueResult myResult = _service.getSelectValue(countryDesc, 0);
BaseRef[] baseRef = myResult.baseRefList;
foreach (BaseRef nsCountryRef in baseRef)
{
// Didn't know how to do this more efficiently
// Get the type for the BaseRef object, get the property for "internalId",
// then finally get it's value as string and assign it to myCountryCode
string myCountryCode = nsCountryRef.GetType().GetProperty("internalId").GetValue(nsCountryRef).ToString();
// Create a new NS_Country object
NS_Country countryToAdd = new NS_Country
{
countryCode = myCountryCode,
countryName = nsCountryRef.name,
// Call to a function to get the enum value based on the name
countryEnum = getCountryEnum(nsCountryRef.name)
};
try
{
// If the country enum was verified in the Countries enum
if (!String.IsNullOrEmpty(countryToAdd.countryEnum))
{
int countryEnumIndex = (int)Enum.Parse(typeof(Country), countryToAdd.countryEnum);
Debug.WriteLine("Enum: " + countryToAdd.countryEnum + ", Enum Index: " + countryEnumIndex);
_out.writeLn("ID: " + countryToAdd.countryCode + ", Name: " + countryToAdd.countryName + ", Enum: " + countryToAdd.countryEnum);
}
}
// There was a problem locating the country enum that was not handled
catch (Exception ex)
{
Debug.WriteLine("Enum: " + countryToAdd.countryEnum + ", Enum Index Not Found");
_out.writeLn("ID: " + countryToAdd.countryCode + ", Name: " + countryToAdd.countryName + ", Enum: Not Found");
}
// Add the countryToAdd object to the CountryList
CountryList.Add(countryToAdd);
}
// Create a JSON - I need this for my javascript
var javaScriptSerializer = new System.Web.Script.Serialization.JavaScriptSerializer();
string jsonString = javaScriptSerializer.Serialize(CountryList);
Debug.WriteLine(jsonString);
In order to get the enum values, I created a function called getCountryEnum:
static string getCountryEnum(string countryName)
{
// Create a dictionary for looking up the exceptions that can't be converted
// Don't know what Netsuite was thinking with these ones ;D
Dictionary<string, string> dictExceptions = new Dictionary<string, string>()
{
{"Congo, Democratic Republic of", "_congoDemocraticPeoplesRepublic"},
{"Myanmar (Burma)", "_myanmar"},
{"Wallis and Futuna", "_wallisAndFutunaIslands"}
};
// Replace with "'s" in the Country names with "s"
string countryName2 = Regex.Replace(countryName, #"\'s", "s");
// Call a function that replaces accented characters with non-accented equivalent
countryName2 = RemoveDiacritics(countryName2);
countryName2 = Regex.Replace(countryName2, #"\W", " ");
string[] separators = {" ","'"}; // "'" required to deal with country names like "Cote d'Ivoire"
string[] words = countryName2.Split(separators, StringSplitOptions.RemoveEmptyEntries);
for (var i = 0; i < words.Length; i++)
{
string word = words[i];
if (i == 0)
{
words[i] = char.ToLower(word[0]) + word.Substring(1);
}
else
{
words[i] = char.ToUpper(word[0]) + word.Substring(1);
}
}
string countryEnum2 = "_" + String.Join("", words);
// return an empty string if the country name contains Deprecated
bool b = countryName.Contains("Deprecated");
if (b)
{
return String.Empty;
}
else
{
// test to see if the country name was one of the exceptions
string test;
bool isExceptionCountry = dictExceptions.TryGetValue(countryName, out test);
if (isExceptionCountry == true)
{
return dictExceptions[countryName];
}
else
{
return countryEnum2;
}
}
}
In the above I used a function, RemoveDiacritics I found here. I will repost the referenced function below:
static string RemoveDiacritics(string text)
{
string formD = text.Normalize(NormalizationForm.FormD);
StringBuilder sb = new StringBuilder();
foreach (char ch in formD)
{
UnicodeCategory uc = CharUnicodeInfo.GetUnicodeCategory(ch);
if (uc != UnicodeCategory.NonSpacingMark)
{
sb.Append(ch);
}
}
return sb.ToString().Normalize(NormalizationForm.FormC);
}
Here are the tricky cases to test any solution you develop with:
// Test tricky names
Debug.WriteLine(getCountryEnum("Curaçao"));
Debug.WriteLine(getCountryEnum("Saint Barthélemy"));
Debug.WriteLine(getCountryEnum("Croatia/Hrvatska"));
Debug.WriteLine(getCountryEnum("Korea, Democratic People's Republic"));
Debug.WriteLine(getCountryEnum("US Minor Outlying Islands"));
Debug.WriteLine(getCountryEnum("Cote d'Ivoire"));
Debug.WriteLine(getCountryEnum("Heard and McDonald Islands"));
// Enums that fail
Debug.WriteLine(getCountryEnum("Congo, Democratic Republic of")); // _congoDemocraticPeoplesRepublic added to exceptions
Debug.WriteLine(getCountryEnum("Myanmar (Burma)")); // _myanmar added to exceptions
Debug.WriteLine(getCountryEnum("Netherlands Antilles (Deprecated)")); // Skip Deprecated
Debug.WriteLine(getCountryEnum("Serbia and Montenegro (Deprecated)")); // Skip Deprecated
Debug.WriteLine(getCountryEnum("Wallis and Futuna")); // _wallisAndFutunaIslands added to exceptions
For my purposes I wanted a JSON object that had all the values for Coutries (Name, Code, Enum, Value). I'll include it here in case anyone is searching for it. The numeric values are useful when you have a 3rd party HTML form that has to forward the information to a Netsuite online form.
Here is a link to the JSON object on Pastebin.
My appologies for the lack of programming knowledge (only really do a bit of javascript), hopefully this additional information will be useful for someone.
I have a class called Customer that has several string properties like
firstName, lastName, email, etc.
I read in the customer information from a csv file that creates an array of the class:
Customer[] customers
I need to remove the duplicate customers having the same email address, leaving only 1 customer record for each particular email address.
I have done this using 2 loops but it takes nearly 5 minutes as there are usually 50,000+ customer records. Once I am done removing the duplicates, I need to write the customer information to another csv file (no help needed here).
If I did a Distinct in a loop how would I remove the other string variables that are a part of the class for that particular customer as well?
Thanks,
Andrew
With Linq, you can do this in O(n) time (single level loop) with a GroupBy
var uniquePersons = persons.GroupBy(p => p.Email)
.Select(grp => grp.First())
.ToArray();
Update
A bit on O(n) behavior of GroupBy.
GroupBy is implemented in Linq (Enumerable.cs) as this -
The IEnumerable is iterated only once to create the grouping. A Hash of the key provided (e.g. "Email" here) is used to find unique keys, and the elements are added in the Grouping corresponding to the keys.
Please see this GetGrouping code. And some old posts for reference.
What's the asymptotic complexity of GroupBy operation?
What guarantees are there on the run-time complexity (Big-O) of LINQ methods?
Then Select is obviously an O(n) code, making the above code O(n) overall.
Update 2
To handle empty/null values.
So, if there are instances where the value of Email is null or empty, the simple GroupBy will take just one of those objects from null & empty each.
One quick way to include all those objects with null/empty value is to use some unique keys at the run time for those objects, like
var tempEmailIndex = 0;
var uniqueNullAndEmpty = persons
.GroupBy(p => string.IsNullOrEmpty(p.Email)
? (++tempEmailIndex).ToString() : p.Email)
.Select(grp => grp.First())
.ToArray();
I'd do it like this:
public class Person {
public Person(string eMail, string Name) {
this.eMail = eMail;
this.Name = Name;
}
public string eMail { get; set; }
public string Name { get; set; }
}
public class eMailKeyedCollection : System.Collections.ObjectModel.KeyedCollection<string, Person> {
protected override string GetKeyForItem(Person item) {
return item.eMail;
}
}
public void testIt() {
var testArr = new Person[5];
testArr[0] = new Person("Jon#Mullen.com", "Jon Mullen");
testArr[1] = new Person("Jane#Cullen.com", "Jane Cullen");
testArr[2] = new Person("Jon#Cullen.com", "Jon Cullen");
testArr[3] = new Person("John#Mullen.com", "John Mullen");
testArr[4] = new Person("Jon#Mullen.com", "Test Other"); //same eMail as index 0...
var targetList = new eMailKeyedCollection();
foreach (var p in testArr) {
if (!targetList.Contains(p.eMail))
targetList.Add(p);
}
}
If the item is found in the collection, you could easily pick (and eventually modify) it with:
if (!targetList.Contains(p.eMail))
targetList.Add(p);
else {
var currentPerson=targetList[p.eMail];
//modify Name, Address whatever...
}