I was given task to build a client server application, using any technology I want. The task was to build a database(doesn't have to be a real database, it can be mocked). the client side should support more than one user/
I didn't use a real database I just created some shares and created a mechanism to update them from time to time using a random value.
I initialized the database with 2 users, I don't need to add users or delete them, just show I can support more than one.
Since I have a background in C# and WPF, I created 3 projects:
1. WPF/MVVM client side
2. common library
3. WebAPI - server side, which "includes" the database.
I would like you to please comment about the correctness of my implementation as if it was a code review for your team. OOP design, usage of client server, please don't take into account I did it with WPF. Assume you have half a day to work on the project and then submit.
I would appreciate any comments or questions.
1. WPF project/ MVVM - I used mvvm light tool kit
MainWindow.xaml
<Window x:Class="Client.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="auto" />
<RowDefinition Height="auto" />
<RowDefinition Height="auto" />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"></ColumnDefinition>
<ColumnDefinition Width="Auto"></ColumnDefinition>
</Grid.ColumnDefinitions>
<TextBlock Grid.Row="0" Grid.Column="0" Text="enter use name: " MinWidth="75"/>
<TextBox Grid.Row="0" Grid.Column="1" MinWidth="75" Text="{Binding UserName,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"/>
<Button Grid.Row="1" Grid.Column="0" Content="Get All Shares" Command="{Binding GetAllSharesCommand,Mode=TwoWay}"/>
<Button Grid.Row="1" Grid.Column="1" Content="Get My Shares" Command="{Binding GetSharePerUserCommand,Mode=TwoWay}"/>
<DataGrid Grid.Row="2" ItemsSource="{Binding Shares}">
</DataGrid>
</Grid>
</Window>
HttpHandler.cs
namespace Client
{
public class HttpHandler
{
private HttpClient client;
public HttpHandler()
{
client = new HttpClient();
client.BaseAddress = new Uri("http://localhost:18702/");
client.DefaultRequestHeaders.Accept.Clear();
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
}
public async Task<IEnumerable<Share>> GetallSharesAsync(string path)
{
IEnumerable<Share> shares = null;
HttpResponseMessage response = await client.GetAsync(path);
if (response.IsSuccessStatusCode)
{
shares = await response.Content.ReadAsAsync<IEnumerable<Share>>();
}
return shares;
}
public async Task<IEnumerable<Share>> GetSharePerUserAsync(string path)
{
IEnumerable<Share> shares = null;
HttpResponseMessage response = await client.GetAsync(path);
if (response.IsSuccessStatusCode)
{
shares = await response.Content.ReadAsAsync<IEnumerable<Share>>();
}
return shares;
}
public async Task<IDictionary<string, int>> GetAllUsersAsync(string path)
{
IDictionary<string, int> users2Id = null;
HttpResponseMessage response = await client.GetAsync(path);
if (response.IsSuccessStatusCode)
{
users2Id = await response.Content.ReadAsAsync<IDictionary<string, int>>();
}
return users2Id;
}
}
}
ClientViewModel.cs
namespace Client
{
public class ClientViewModel : ViewModelBase
{
private ObservableCollection<Share> _shares;
public ObservableCollection<Share> Shares
{
get { return _shares; }
set { _shares = value; }
}
private string _userName;
public string UserName
{
get { return _userName; }
set
{
_userName = value;
RaisePropertyChanged("UserName");
GetAllSharesCommand.RaiseCanExecuteChanged();
}
}
private RelayCommand _getAllSharesCommand;
public RelayCommand GetAllSharesCommand
{
get { return _getAllSharesCommand; }
set
{
_getAllSharesCommand = value;
}
}
private RelayCommand _GetSharesPerUserCommand;
public RelayCommand GetSharePerUserCommand
{
get { return _GetSharesPerUserCommand; }
set { _GetSharesPerUserCommand = value; }
}
private HttpHandler handler;
private Dictionary<string, int> _userName2Id;
public ClientViewModel()
{
GetAllSharesCommand = new RelayCommand(ExecuteGetAllShares, CanExecuteGetAllShares);
GetSharePerUserCommand = new RelayCommand(ExecuteGetSharePerUserCommand, CanExecuteGetSharePerUserCommand);
handler = new HttpHandler();
Shares = new ObservableCollection<Share>();
GetUsers();
}
private async void GetUsers()
{
IDictionary<string, int> userNames2ID = await handler.GetAllUsersAsync("api/users");
_userName2Id = new Dictionary<string, int>(userNames2ID);
}
private bool CanExecuteGetSharePerUserCommand()
{
return !String.IsNullOrEmpty(UserName);
}
private async void ExecuteGetSharePerUserCommand()
{
string temp = "api/shares" + "/" + _userName2Id[UserName];
try
{
IEnumerable<Share> tempShares = await handler.GetSharePerUserAsync(temp);
Shares.Clear();
foreach (var item in tempShares)
{
Shares.Add(item);
}
}
catch (Exception)
{
throw;
}
}
public bool CanExecuteGetAllShares()
{
return !String.IsNullOrEmpty(UserName);
}
public async void ExecuteGetAllShares()
{
try
{
IEnumerable<Share> tempShares = await handler.GetallSharesAsync("api/shares");
Shares.Clear();
foreach (var item in tempShares)
{
Shares.Add(item);
}
}
catch (Exception)
{
throw;
}
}
}
}
2.Common - project
Share.cs
namespace Common
{
public class Share
{
public int Id { get; set; }
public string Name { get; set; }
public double Price { get; set; }
}
}
3.Server - WebApi project(yea I know what a great name)
WebApiConfig.cs
namespace SharesApp
{
public static class WebApiConfig
{
public static void Register(HttpConfiguration config)
{
config.MapHttpAttributeRoutes();
config.Routes.MapHttpRoute(
name: "DefaultApi",
routeTemplate: "api/{controller}/{id}",
defaults: new { id = RouteParameter.Optional }
);
}
}
}
Controllers folder
SharesController.cs
namespace SharesApp.Controllers
{
public class SharesController : ApiController
{
//this is a mock for a real database, i'm not sure where do I need to connect to the real DB
private static IDataBase _dataBase;
public SharesController()
{
if (_dataBase == null)
{
_dataBase = new SharesDataBase();
}
}
public IEnumerable<Share> GetAllShares()
{
try
{
return _dataBase.GetAllShares();
}
catch (Exception)
{
throw;
}
}
public IHttpActionResult GetUpdatedShares(int id)
{
IEnumerable<Share> share = null;
try
{
share = _dataBase.GetShareById(id);
}
catch (Exception)
{
throw;
}
if (share == null)
{
return NotFound();
}
return Ok(share);
}
}
UsersController .cs
namespace SharesApp.Controllers
{
public class UsersController : ApiController
{
private Dictionary<string, int> _userName2Id;
public UsersController()
{
_userName2Id = new Dictionary<string, int>();
_userName2Id.Add("user10", 1);
_userName2Id.Add("user20", 2);
}
public IDictionary<string, int> GetAllUserNames()
{
return _userName2Id;
}
public string GetUserNameById(int id)
{
if (!_userName2Id.ContainsValue(id))
{
return null;
}
return _userName2Id.FirstOrDefault(x => x.Value == id).Key;
}
}
}
Models folder
IDataBase.cs
namespace SharesApp.Models
{
public interface IDataBase
{
IEnumerable<Share> GetAllShares();
IEnumerable<Share> GetShareById(int id);
}
}
SharesDataBase.cs
namespace SharesApp.Models
{
public class SharesDataBase : IDataBase
{
//user name to list of shares names
const string INTC = "INTC";
const string MSFT = "MSFT";
const string TEVA = "TEVA";
const string YAHOO = "YAHOO";
const string P500 = "P500";
private List<Share> _shares;
private Random _random;
private int _maximum = 100;
private int _minimum = 1;
public Dictionary<int, List<string>> User2Shares { get; set; }
private Object thisLock = new Object();
public SharesDataBase()
{
_random = new Random();
User2Shares = new Dictionary<int, List<string>>();
//init the shares list
_shares = new List<Share>
{
new Share { Id = 1, Name = INTC, Price = 1 },
new Share { Id = 2, Name = MSFT, Price = 3.75 },
new Share { Id = 3, Name = TEVA, Price = 16.99},
new Share { Id = 4, Name = YAHOO, Price = 11.0},
new Share { Id = 5, Name = P500, Price = 5.55},
};
//init the users
User2Shares.Add(1, new List<string>() { INTC, MSFT, TEVA });
User2Shares.Add(2, new List<string>() { YAHOO, P500, TEVA });
Task.Run(()=>UpdateShares());
}
private void UpdateShares()
{
while (true)
{
System.Threading.Thread.Sleep(1000);// wait for 1 sec
lock (thisLock)
{
foreach (var item in _shares)
{
int tempRandom = _random.Next(1, 1000);
if (tempRandom % 100 == 0)
{
item.Price = _random.NextDouble() * (_maximum - _minimum) + _minimum;
}
}
}
}
}
public IEnumerable<Share> GetAllShares()
{
return _shares;
}
public IEnumerable<Share> GetShareById(int id)
{
if (!User2Shares.ContainsKey(id))
{
return null;
}
var listOfShares = User2Shares[id];
if (listOfShares.Count == 0)
{
//this userName doesn't have any shares
return null;
}
List<Share> sharesList = new List<Share>();
foreach (var name in listOfShares)
{
var res = _shares.FirstOrDefault(x => x.Name == name);
if (res != null)
{
sharesList.Add(res);
}
//share is missing from the server
}
return sharesList;
}
}
