I am developing an application to allow a user to enter their employee details of their company into a database. So far I am experimenting with WPF and trying to implement MVVM within my application while using Entity Framework.
I'm creating a Master-Detail application, and have been researching into how to achieve this using MVVM, as I'm very much new to it all.
One of the ways in which I have tried is by creating a property within my View-Model called SelectedEmployee and then binding it to a List View in my xaml, like so;
public Employee _SelectedEmployee;
public Employee SelectedEmployee
{
get
{
return _SelectedEmployee;
}
set
{
if (_SelectedEmployee == value)
return;
_SelectedEmployee = value;
OnPropertyChanged("SelectedEmployee");
}
}
<ListView HorizontalAlignment="Left" Name="listview" VerticalAlignment="Bottom" ScrollViewer.HorizontalScrollBarVisibility="Visible"
IsSynchronizedWithCurrentItem="True"
ItemsSource="{Binding LoadEmployee}" SelectionMode="Single" SelectedItem="{Binding SelectedEmployee, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" Height="150" Grid.Row="1">
I then have a method that allows the user to update a SelectedItem within the List View. But this is where the problem occurs. When I select an item from the List View, it only updates the first row from the database and not the row I wanted to select.
Here's the method;
public void UpdateEmployee(Employee emp)
{
using (DBEntities context = new DBEntities())
{
emp = context.Employees.Where(e => e.EmployeeID == SelectedEmployee.EmployeeID).FirstOrDefault();
emp.Title = Title;
emp.FirstName = FirstName;
emp.Surname = Surname;
emp.Position = Position;
emp.DateOfBirth = DateOfBirth;
emp.Address = Address;
emp.Country = Country;
emp.Postcode = Postcode;
emp.PhoneNumber = PhoneNumber;
emp.MobileNumber = MobileNumber;
emp.FaxNumber = FaxNumber;
emp.Email = Email;
emp.NINumber = NINumber;
emp.ChargableResource = ChargableResource;
emp.ChargeOutRate = ChargeOutRate;
emp.TimeSheetRequired = TimeSheetRequired;
emp.WorkShift = WorkShift;
emp.BenefitsProvided = BenefitsProvided;
context.Employees.ApplyCurrentValues(emp);
context.SaveChanges();
}
}
I have bound my properties within my view model to the text-boxes within my xaml and then implementing OnPropertyChanged.
I am also using Commands to limit the amount of code-behind as its important for testability and maintainability.
Here is the command method to update;
private ICommand showUpdateCommand;
public ICommand ShowUpdateCommand
{
get
{
if (showUpdateCommand == null)
{
showUpdateCommand = new RelayCommand(this.UpdateFormExecute, this.UpdateFormCanExecute);
}
return showUpdateCommand;
}
}
private bool UpdateFormCanExecute()
{
return !string.IsNullOrEmpty(FirstName) ...
}
private void UpdateFormExecute()
{
UpdateOrganisationTypeDetail();
}
As I am new to MVVM, I'm not quite sure what I am doing wrong so would appreciate some input please :).
Then perhaps the problem is with your updating. I don't really understand what your trying to do with listview, but since it's not working in a simple datagrid this might help. it's not so much an answer as something that I wrote to find your error that happens not to contain your error. please do comment if anything is awry.
public partial class MainWindow : Window
{
private static MainViewModel _mainViewModel = new MainViewModel();
public static ObservableCollection<Employee> staff = new ObservableCollection<Employee>();
public MainWindow()
{
InitializeComponent();
this.DataContext = _mainViewModel;
dataGrid1.DataContext = staff;
listview.DataContext = staff;
Employee Employee1 = new Employee();
Employee1.name = "Jeff";
staff.Add(Employee1);
Employee Employee2 = new Employee();
Employee2.name = "Jefferson";
staff.Add(Employee2);
Employee2.name = "Tim";
}
}
public class Employee
{
public string name { get; set; }
}
public class MainViewModel : INotifyPropertyChanged
{
private string _SelectedEmployee;
public string SelectedEmployee
{
get { return _SelectedEmployee; }
set
{
_SelectedEmployee = value;
NotifyPropertyChanged("SelectedEmployee");
}
}
public event PropertyChangedEventHandler PropertyChanged;
public void NotifyPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}
Related
I see several other posts about this but I cannot seem to understand exactly how to get this working properly for my usage.
Here is what I have in a nutshell.
I have two Comboboxes--Role and Position.
I have both of these bound to an ObservableCollection which has Enum Values Converted to strings loaded into it on instantiation.
<ComboBox x:Name="empRoleCB" ItemsSource="{Binding Role}" SelectedItem="{Binding RoleStr}"/>
<ComboBox x:Name="empPositionCB" ItemsSource="{Binding Pos}" SelectedItem="{Binding PosStr}"/>
In my ViewModel:
public abstract class EmployeeMenuVMBase : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected bool SetProperty<T>(ref T field, T newValue, [CallerMemberName] string propertyName = null)
{
if(!EqualityComparer<T>.Default.Equals(field, newValue))
{
field = newValue;
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
return true;
}
return false;
}
}
class EmployeeMenuVM : EmployeeMenuVMBase
{
private ObservableCollection<string> _pos = new ObservableCollection<string>(Enum.GetNames(typeof(Global.Positions)));
private ObservableCollection<string> _role = new ObservableCollection<string>(Enum.GetNames(typeof(Global.Roles)));
public ObservableCollection<string> Pos { get => _pos; }
public ObservableCollection<string> Role { get => _role; }
public string RoleStr
{
get => _roleStr;
set => SetProperty(ref _roleStr, value);
}
public string PosStr
{
get => _posStr;
set => SetProperty(ref _posStr, value);
}
}
What I want to happen is when a Role is selected, based on that selection, only certain Positions should be shown. For instance if I select "Customer Service" as a Role, then Position should only contain "Manager", "CSS" and "None". If Role is "Admin" then Position should only contain "None", and so on and so forth.
The struggle I have is how to filter this properly. I see something with using CollectionViewSource but I am unsure how to get this to work with my example.
I have 5 roles and each role will have a different list of positions that need to be shown.
What is the best way to make this work with MINIMAL extra code or XAML?
One of the things I really dislike about WPF is seemingly simple things need huge amounts of code to make them work properly many times.
First, if you think that WPF is complicated. So, you are using it wrongly.
I suggest you to use the Filter of CollectionViewSource as flow:
<ComboBox x:Name="empPositionCB" ItemsSource="{Binding MyPositionFilter}" SelectionChanged="RoleComboBox_SelectionChanged" ....../>
public ICollectionView MyPositionFilter { get; set; }
//ctor
public MyUserControlOrWindow()
{
//Before InitComponent()
this.MyPositionFilter = new CollectionViewSource { Source = MyPosObservableCollection }.View;
InitComponent();
}
public void RoleComboBox_SelectionChanged(object sender,EventArgs e)
{
//Get the selected Role (the ? is to prevent NullException (VS 2015 >))
Role r = empRoleCB.SelectedItem as Role;
//Apply the filter
this.MyPositionFilter.Filter = item =>
{
//Make you sure to convert correcteley your Enumeration, I used it here like a class
Position p = item as Position;
//Put your condition here. For example:
return r.ToLowers().Contains(p.ToLower());
//Or
return (r != null && r.Length >= p.Length);
};
}
The filter does not change your Collection, All hidden item stay in your ObservableCollection.
This can all be done in your ViewModel by changing the value of the Positions (Pos) observable collection when the role changes.
class EmployeeMenuVM : EmployeeMenuVMBase
{
public EmployeeMenuVM()
{
var emptyPositions = new List<Global.Positions>()
{ Global.Positions.None };
_rolePositions.Add(Global.Roles.None, emptyPositions);
var customerServicePositions = new List<Global.Positions>()
{ Global.Positions.None, Global.Positions.CSS, Global.Positions.Manager };
_rolePositions.Add(Global.Roles.CustomerService, customerServicePositions);
}
private Dictionary<Global.Roles, List<Global.Positions>> _rolePositions = new Dictionary<Global.Roles, List<Global.Positions>>();
private string _roleStr;
private string _posStr;
private ObservableCollection<string> _pos = new ObservableCollection<string>(Enum.GetNames(typeof(Global.Positions)));
private ObservableCollection<string> _role = new ObservableCollection<string>(Enum.GetNames(typeof(Global.Roles)));
public ObservableCollection<string> Pos
{
get => _pos;
set
{
SetProperty(ref _pos, value);
}
}
public ObservableCollection<string> Role
{
get => _role;
}
public string RoleStr
{
get => _roleStr;
set
{
if (SetProperty(ref _roleStr, value))
{
Global.Roles role = (Global.Roles)Enum.Parse(typeof(Global.Roles), value);
var positions = _rolePositions[role].Select(p => p.ToString());
Pos = new ObservableCollection<string>(positions);
}
}
}
public string PosStr
{
get => _posStr;
set => SetProperty(ref _posStr, value);
}
}
Here is a working tester code just to see the main idea of how to do the filtering:
MainWindow.xaml
<Window x:Class="WpfApplication3.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:WpfApplication3"
x:Name="ThisView"
mc:Ignorable="d"
Title="MainWindow" Height="350" Width="600">
<StackPanel Orientation="Horizontal">
<ComboBox ItemsSource="{Binding Path=Roles, ElementName=ThisView}"
SelectedItem="{Binding Path=SelectedRole, ElementName=ThisView}"
Width="300" Height="60"/>
<ComboBox ItemsSource="{Binding Path=PositionCollectionView, ElementName=ThisView}" Width="300" Height="60"/>
</StackPanel>
</Window>
MainWindow.xaml.cs
public partial class MainWindow : Window, INotifyPropertyChanged
{
public ICollectionView PositionCollectionView { get; set; }
public ObservableCollection<string> Roles { get; set; } = new ObservableCollection<string>();
public ObservableCollection<string> Positions { get; set; } = new ObservableCollection<string>();
private string _selectedRole = String.Empty;
public string SelectedRole
{
get { return _selectedRole; }
set
{
_selectedRole = value;
OnPropertyChanged();
//This Refresh activates the Filter again, so that every time you select a role, this property will call it.
PositionCollectionView.Refresh();
}
}
public MainWindow()
{
PositionCollectionView = CollectionViewSource.GetDefaultView(Positions);
PositionCollectionView.Filter = PositionsFilter;
//use you enums here
Roles.Add("Role1");
Roles.Add("Role2");
Roles.Add("Role3");
Roles.Add("Role4");
Positions.Add("Position1");
Positions.Add("Position2");
Positions.Add("Position3");
Positions.Add("Position4");
InitializeComponent();
}
private bool PositionsFilter(object position)
{
bool result = true;
//place your code according to the Role selected to decide wheather "position" should be in the position list or not
return result;
}
public event PropertyChangedEventHandler PropertyChanged;
[NotifyPropertyChangedInvocator]
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
Hope it helps..
Basic question from a novice. I've been stuck on this and have read through a lot of material and several similar questions on SO; hopefully not a completely duplicate question. I simplified the code as much as I know how to.
I'm trying to make the ListView show a filtered ObservableCollection) property (as the ItemsSource?), based on the selection in the ComboBox.
Specifically, which "meetings" have this "coordinator" related to it.
I'm not seeing any data errors in the output while it's running and debugging shows the properties updating correctly, but the ListView stays blank. I'm trying to avoid any code-behind on the View, there is none currently.
Thanks!
public class ViewModel : INotifyPropertyChanged
{
private ObservableCollection<Meeting> meetings;
public ObservableCollection<Meeting> Meetings
{
get
{
return meetings;
}
set
{
meetings = value;
OnPropertyChanged("ListProperty");
OnPropertyChanged("Meetings");
}
}
private string coordinatorSelected;
public string CoordinatorSelected
{
get
{
return coordinatorSelected;
}
set
{
coordinatorSelected = value;
Meetings = fakeDB.Where(v => v.CoordinatorName == CoordinatorSelected) as ObservableCollection<Meeting>;
}
}
private ObservableCollection<string> comboProperty = new ObservableCollection<string> { "Joe", "Helen", "Sven" };
public ObservableCollection<string> ComboProperty
{
get
{
return comboProperty;
}
}
private ObservableCollection<Meeting> fakeDB = new ObservableCollection<Meeting>() { new Meeting("Joe", "Atlas"), new Meeting("Sven", "Contoso"), new Meeting("Helen", "Acme") };
public ObservableCollection<Meeting> ListProperty
{
get
{
return Meetings;
}
}
public class Meeting
{
public string CoordinatorName { get; set; }
public string ClientName { get; set; }
public Meeting(string coordinatorName, string clientName)
{
CoordinatorName = coordinatorName;
ClientName = clientName;
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string propertyName)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
XAML:
<Window.Resources>
<local:ViewModel x:Key="VM"></local:ViewModel>
</Window.Resources>
<DockPanel DataContext="{StaticResource ResourceKey=VM}">
<ComboBox Margin="10" ItemsSource="{Binding ComboProperty}" SelectedItem="{Binding CoordinatorSelected}" DockPanel.Dock="Top"/>
<ListView Margin="10" ItemsSource="{Binding ListProperty, UpdateSourceTrigger=PropertyChanged}" DisplayMemberPath="ClientName"/>
</DockPanel>
Update:
This seems to show that the lambda is returning a Meeting object but the assignment to Meetings is failing. Is this an error in casting maybe?
Thanks again.
You always have to change a property's backing field before you fire a PropertyChanged event. Otherwise a consumer of the event would still get the old value when it reads the property.
Change the Meetings property setter like this:
public ObservableCollection<Meeting> Meetings
{
get
{
return meetings;
}
set
{
meetings = value;
OnPropertyChanged("ListProperty");
OnPropertyChanged("Meetings");
}
}
I believe I've found two solutions to the same problem. The error pointed out #Clemens was also part of the solution. The Meetings property problem is solved if I change ListProperty and Meetings to IEnumerable. Alternatively this approach without changing the type, which I believe invokes the collection's constructor with the filtered sequence as an argument.
set
{
coordinatorSelected = value;
var filteredList = fakeDB.Where(v => v.CoordinatorName == coordinatorSelected);
Meetings = new ObservableCollection<Meeting>(filteredList);
OnPropertyChanged("ListProperty");
}
I am really struggling with data binding and the MVVM Methodology, though I like the concept I am just struggling. I have created a WPF for that has multiple comboboxes and a button. The first combobox will list database instance names. the remaining comboboxes will be populated after the button is clicked. Since I am having issues with the first, database instances, combobox I will only show my code for that. When the application starts up the combobox is loaded and the first item is selected, as expected. The issue is when I select a new name my method that I expect to get called does not. Can someone help me to understand why my method public DBInstance SelectedDBInstance is not getting executed when I have this in my XAML, SelectedValue="{Binding SelectedDBInstance, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}?
Here is my XAML for the database instances combobox. One question I have here is the "value" fpr SelectedValuePath, if I change it to say "DBInstanceName" it does not work.
<ComboBox x:Name="cbxRLFDBInstances" ItemsSource="{Binding DBInstances}"
SelectedValue="{Binding SelectedDBInstance, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
SelectedValuePath="value" DisplayMemberPath="DBInstanceName"/>
Here is my ViewModel Code:
namespace DatabaseTest.ViewModel
{
class RLFDatabaseTableViewModel : INotifyPropertyChanged
{
Utilities dbtUtilities = new Utilities();
public RelayCommand LoadDBInfoCommand
{
get;
set;
}
public RLFDatabaseTableViewModel()
{
LoadDBInstances();
LoadDBInfoCommand = new RelayCommand(LoadDBInfo);
}
public ObservableCollection<DBInstance> DBInstances
{
get;
set;
}
public void LoadDBInstances()
{
ObservableCollection<DBInstance> dbInstances = new ObservableCollection<DBInstance>();
DataTable dt = SmoApplication.EnumAvailableSqlServers(false);
dbInstances.Add(new DBInstance { DBInstanceName = "fal-conversion\\mun2012ci" });
dbInstances.Add(new DBInstance { DBInstanceName = "fal-conversion\\mun2014ci" });
if (dt.Rows.Count > 0)
{
foreach (DataRow dr in dt.Rows)
{
dbInstances.Add(new DBInstance { DBInstanceName = dr["Name"].ToString() });
}
}
DBInstances = dbInstances;
}
private DBInstance _selectedDBInstance;
public DBInstance SelectedDBInstance
{
get
{
return _selectedDBInstance;
}
set
{
_selectedDBInstance = value;
RaisePropertyChanged("SelectedDBInstance");
//ClearComboBoxes();
}
}
}
}
Here is my Model code. When I step through the code this method, public string DBInstanceName, gets executed multiple time. I do not know why and it is seems wasteful to me.
namespace DatabaseTest.Model
{
public class RLFDatabaseTableModel { }
public class DBInstance : INotifyPropertyChanged
{
private string strDBInstance;
public override string ToString()
{
return strDBInstance;
}
public string DBInstanceName
{
get
{
return strDBInstance;
}
set
{
if (strDBInstance != value)
{
strDBInstance = value;
RaisePropertyChanged("DBInstanceName");
}
}
}
public event PropertyChangedEventHandler PropertyChanged;
private void RaisePropertyChanged(string property)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(property));
}
}
}
You should bind the SelectedItem property of the ComboBox to the SelectedDBInstance property and get rid of the SelectedValuePath:
<ComboBox x:Name="cbxRLFDBInstances" ItemsSource="{Binding DBInstances}"
SelectedItem="{Binding SelectedDBInstance, UpdateSourceTrigger=PropertyChanged}"
DisplayMemberPath="DBInstanceName"/>
The SelectedValuePath property is only used when you want to bind to a source property that is not of the same type as the item in the ItemsSource collection.
To select an item initially you should set the SelectedDBInstance property to an item that is present in the DBInstances collection:
public RLFDatabaseTableViewModel()
{
LoadDBInstances();
LoadDBInfoCommand = new RelayCommand(LoadDBInfo);
SelectedDBInstance = DBInstances[0]; //selected the first item
}
I have the following Classes:
Item
public class Item : INotifyPropertyChanged, IDataErrorInfo
{
private int? id;
public int? ID
{
get
{ return id; }
set
{ id = value; }
}
private string name;
public string Name
{
get
{ return name; }
set
{
if (value != name)
{
ClearError("Name");
if (string.IsNullOrEmpty(value) || value.Trim() == "")
SetError("Name", "Required Value");
name = value;
}
}
}
private List<MedicineComposition> medicineCompositions;
public List<MedicineComposition> MedicineCompositions
{
set { medicineCompositions = value; }
get { return medicineCompositions; }
}
}
MedicineComposition
public class MedicineComposition : INotifyPropertyChanged, IDataErrorInfo
{
private int? id;
public int? ID
{
get
{ return id; }
set
{ id = value; }
}
private Item item;
public Item Item
{
get
{ return item; }
set
{
if (item != value)
{
ClearError("Item");
if (value == null)
SetError("Item", "Required Value");
item = value;
}
}
}
private Component component;
public Component Component
{
get
{ return component; }
set
{
if (component != value)
{
ClearError("Component");
if (value == null)
SetError("Component", "Required Value");
component = value;
}
}
}
}
Component which has only id and Name
and the following functions that bring data from database and make the list of my objects:
GetItems in Item Class
public static List<Item> GetAllItems
{
get
{
List<Item> MyItems = new List<Item>();
SqlConnection con = new SqlConnection(BaseDataBase.ConnectionString);
SqlCommand com = new SqlCommand("sp_Get_All_Item", con);
com.CommandType = System.Data.CommandType.StoredProcedure;
try
{
con.Open();
SqlDataReader rd = com.ExecuteReader();
while (rd.Read())
{
Item i = new Item();
if (!(rd["ID"] is DBNull))
i.ID = System.Int32.Parse(rd["ID"].ToString());
i.Name = rd["Name"].ToString();
i.MedicineCompositions = MedicineComposition.GetAllByItem(i);
MyItems.Add(i);
}
rd.Close();
}
catch
{
MyItems = null;
}
finally
{
con.Close();
}
return MyItems;
}
GetAllByItem in MedicalCompositions
public static List<MedicineComposition> GetAllByItem(Item i)
{
List<MedicineComposition> MyMedicineCompositions = new List<MedicineComposition>();
SqlConnection con = new SqlConnection(BaseDataBase.ConnectionString);
SqlCommand com = new SqlCommand("sp_Get_ByItemID_MedicineComposition", con);
com.CommandType = System.Data.CommandType.StoredProcedure;
SqlParameter pr = new SqlParameter("#ID", i.ID);
com.Parameters.Add(pr);
try
{
con.Open();
SqlDataReader rd = com.ExecuteReader();
while (rd.Read())
{
MedicineComposition m = new MedicineComposition() { };
if (!(rd["ID"] is DBNull))
m.ID = Int32.Parse(rd["ID"].ToString());
if (!(rd["ComponentID"] is DBNull))
m.Component = Component.GetByID(Int32.Parse(rd["ComponentID"].ToString()));
m.Item = i;
MyMedicineCompositions.Add(m);
}
rd.Close();
}
catch
{
MyMedicineCompositions = null;
}
finally
{
con.Close();
}
return MyMedicineCompositions;
}
it's like to use mvvm because it let you deal with objects instead of datatable, but when i use the previous shape of class structure i have the following problems:
i have at least 1000 records in Item Table in database so when i call GetAllItems i have slow performance especially when the database in not on local computer.
i tried to load Items when splash screen on, it takes times but take medium performance
on each update on Item table i should recall GetAllItems so slow back
my questions is where is the problem that i have in creating class, and is this the best way to structure the class in mvvm
I dont think your user need to see all the 1000 items at a glance, not even the many thousand of composition and components related.
I situations like this I would:
Filter the data. Ask the user for the Item name, category or what else.
Delay load. At first load only the (filtered) Items. When the user select an Item switch to an "Item details" View and load the related data (composition and components).
A few things you could improve here, for example:
Given we are talking about MedicalComposition it might not be best of ideas to have nullable unique identifier
If you have multiple classes consisting only of id and name you could use KeyValuePair<> or Tuple<> instead
Implement a base class, say ModelBase that implements INotifyPropertyChanged
Implement repository pattern for database related action, cache/page results if possible
If not yet done, move data- and/or time intensive operations into separate thread(s)
It's a little confusing that on Item you have IEnumerable of MedicineCompositions but also, in MedicineComposition you have the Item, too? Maybe you don't need it at all or related Item.Id would be enough?
You could add a method to your repository to only return items that have been added/modified/removed since <timestamp> and only update what is necessary in your Items collection
You could make some of the properties Lazy<>
Utilize TAP (Task-based Asynchronous Pattern)
Below is "one go" for your problem w/o blocking the UI thread. It's far from complete but still. Thread.Sleeps in repositories are mimicking your database query delays
View\MainWindow.xaml
Codebehind contains just InitializeComponents.
<Window x:Class="WpfApplication1.View.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:viewModel="clr-namespace:WpfApplication1.ViewModel"
Title="MainWindow"
Height="300"
Width="250">
<Window.DataContext>
<viewModel:MainViewModel />
</Window.DataContext>
<!-- Layout root -->
<Grid x:Name="ContentPanel" Margin="12,0,12,0">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="*" />
</Grid.RowDefinitions>
<!-- Status label -->
<Label Grid.Row="0"
HorizontalAlignment="Stretch"
VerticalAlignment="Top"
Background="Bisque"
Margin="0,3,0,3"
Content="{Binding Status}" />
<!-- Controls -->
<StackPanel Grid.Row="1">
<Label Content="Items" />
<!-- Items combo -->
<ComboBox HorizontalAlignment="Stretch"
MaxDropDownHeight="120"
VerticalAlignment="Top"
Width="Auto"
Margin="0,0,0,5"
ItemsSource="{Binding Items}"
SelectedItem="{Binding SelectedItem}"
DisplayMemberPath="Name" />
<!-- Medicine components -->
<ItemsControl ItemsSource="{Binding SelectedItem.MedicineCompositions}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<StackPanel>
<TextBlock Text="{Binding Name}" />
<!-- Components -->
<ItemsControl ItemsSource="{Binding Components}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<TextBlock>
<Run Text=" * " />
<Run Text="{Binding Name}" />
</TextBlock>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</StackPanel>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</StackPanel>
</Grid>
</Window>
ViewModel\MainViewModel
public class MainViewModel : ViewModelBase
{
private string _status;
private Item _selectedItem;
private ObservableCollection<Item> _items;
public MainViewModel()
:this(new ItemRepository(), new MedicineCompositionRepository())
{}
public MainViewModel(IRepository<Item> itemRepository, IRepository<MedicineComposition> medicineCompositionRepository)
{
ItemRepository = itemRepository;
MedicineCompositionRepository = medicineCompositionRepository;
Task.Run(() => LoadItemsData());
}
public IRepository<Item> ItemRepository { get; set; }
public IRepository<MedicineComposition> MedicineCompositionRepository { get; set; }
public Item SelectedItem
{
get { return _selectedItem; }
set
{
_selectedItem = value;
OnPropertyChanged();
Task.Run(() => LoadMedicineCompositionsData(_selectedItem));
}
}
public ObservableCollection<Item> Items
{
get { return _items; }
set { _items = value; OnPropertyChanged(); }
}
public string Status
{
get { return _status; }
set { _status = value; OnPropertyChanged(); }
}
private async Task LoadItemsData()
{
Status = "Loading items...";
var result = await ItemRepository.GetAll();
Items = new ObservableCollection<Item>(result);
Status = "Idle";
}
private async Task LoadMedicineCompositionsData(Item item)
{
if (item.MedicineCompositions != null)
return;
Status = string.Format("Loading compositions for {0}...", item.Name);
var result = await MedicineCompositionRepository.GetById(item.Id);
SelectedItem.MedicineCompositions = result;
Status = "Idle";
}
}
Model
public class Component : ModelBase
{}
public class MedicineComposition : ModelBase
{
private IEnumerable<Component> _component;
public IEnumerable<Component> Components
{
get { return _component; }
set { _component = value; OnPropertyChanged(); }
}
}
public class Item : ModelBase
{
private IEnumerable<MedicineComposition> _medicineCompositions;
public IEnumerable<MedicineComposition> MedicineCompositions
{
get { return _medicineCompositions; }
set { _medicineCompositions = value; OnPropertyChanged(); }
}
}
public abstract class ModelBase : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private int _id;
private string _name;
public int Id
{
get { return _id; }
set { _id = value; OnPropertyChanged(); }
}
public string Name
{
get { return _name; }
set { _name = value; OnPropertyChanged(); }
}
[NotifyPropertyChangedInvocator]
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
var handler = PropertyChanged;
if (handler != null)
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
Repository
public interface IRepository<T> where T : class
{
Task<IEnumerable<T>> GetAll();
Task<IEnumerable<T>> GetById(int id);
}
public class ItemRepository : IRepository<Item>
{
private readonly IList<Item> _mockItems;
public ItemRepository()
{
_mockItems = new List<Item>();
for (int i = 0; i < 100; i++)
_mockItems.Add(new Item { Id = i, Name = string.Format("Item #{0}", i), MedicineCompositions = null });
}
public Task<IEnumerable<Item>> GetAll()
{
Thread.Sleep(1500);
return Task.FromResult((IEnumerable<Item>) _mockItems);
}
public Task<IEnumerable<Item>> GetById(int id)
{
throw new NotImplementedException();
}
}
public class MedicineCompositionRepository : IRepository<MedicineComposition>
{
private readonly Random _random;
public MedicineCompositionRepository()
{
_random = new Random();
}
public Task<IEnumerable<MedicineComposition>> GetAll()
{
throw new NotImplementedException();
}
public Task<IEnumerable<MedicineComposition>> GetById(int id)
{
// since we are mocking, id is actually ignored
var compositions = new List<MedicineComposition>();
int compositionsCount = _random.Next(1, 3);
for (int i = 0; i <= compositionsCount; i++)
{
var components = new List<Component>();
int componentsCount = _random.Next(1, 3);
for (int j = 0; j <= componentsCount; j++)
components.Add(new Component {Id = j, Name = string.Format("Component #1{0}", j)});
compositions.Add(new MedicineComposition { Id = i, Name = string.Format("MedicalComposition #{0}", i), Components = components });
}
Thread.Sleep(500);
return Task.FromResult((IEnumerable<MedicineComposition>) compositions);
}
}
Instead of returning List, return IEnumerable and yield results as they are needed. Obviously it would only improve performance, when you are not reading all the results, which is actually true in most cases. To do that you would have to remove catch, because you cannot have yield and catch together. The catch could go around con.Open and ExecuteReader and in catch you can yield break:
public static IEnumerable<MedicineComposition> GetAllByItem(Item i)
{
SqlConnection con = new SqlConnection(BaseDataBase.ConnectionString);
SqlCommand com = new SqlCommand("sp_Get_ByItemID_MedicineComposition", con);
com.CommandType = System.Data.CommandType.StoredProcedure;
SqlParameter pr = new SqlParameter("#ID", i.ID);
com.Parameters.Add(pr);
try
{
SqlDataReader rd;
try
{
con.Open();
rd = com.ExecuteReader();
}
catch { yield break;}
while (rd.Read())
{
MedicineComposition m = new MedicineComposition() { };
if (!(rd["ID"] is DBNull))
m.ID = Int32.Parse(rd["ID"].ToString());
if (!(rd["ComponentID"] is DBNull))
m.Component = Component.GetByID(Int32.Parse(rd["ComponentID"].ToString()));
m.Item = i;
yield return m;
}
rd.Close();
}
finally
{
con.Close();
}
}
Now in case of an exception this is no longer returning null, but can return few items or even empty enumeration. I would rather move the catch to caller of this getter.
If you need for some reason count of returned items, call GetAllByItem(item).ToArray(). This will enumerate all the items once and gets the length for you. Definitely don't call the enumeration twice to get the length and then enumerate the items:
var length = GetAllByItem(item).Count();// this will get all the items from the db
foreach(var i in GetAllByItem(item)) // this will get all the items from the db again
Rather do this:
var list = GetAllByItem(item); // this will get all the items and now you have the length and the items.
Obviously if you need the length for some reason, there is no point in changing to IEnumerable, only for better abstraction.
Other improvement could be, to create the connection only once instead of every time on calling the getter. That is possible only, if you know it won't cause any harm.
Assign the dataset into the constructor of your ObservableCollection property. Else your view will update via a PropertyChanged notification for each item that your ObservableCollection performs an Add operation.
Try this:
var items = services.LoadItems();
myObservableCollection = new ObservableCollection<somedatatype>(items);
This type of assignment will notify your view once instead of the current way your implementation does which is 1000 times.
Im having a real headache binding my items to pushpins on a silverlight bing map.
Ive spent all day trying to get my collection sorted and now just cant get the pushpins to show up.
The items appear to be there as when you do a breakpoint on the last line as per the image below, all 143 items are there in _PushPins:
Any help welcome. many thanks.
Here is the code:
namespace observable_collection_test
{
public partial class Map : PhoneApplicationPage
{
public Map()
{
InitializeComponent();
GetItems();
}
private ObservableCollection<SItem2> pushPins;
public ObservableCollection<SItem2> PushPins
{
get { return this.pushPins; }
set
{
this.pushPins = value;
this.OnPropertyChanged("PushPins");
}
}
public event PropertyChangedEventHandler PropertyChanged;
public void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
public void GetItems()
{
var document = XDocument.Load("ListSmall.xml");
if (document.Root == null)
return;
var xmlns = XNamespace.Get("http://www.blah");
var events = from ev in document.Descendants("item")
select new
{
Latitude = Convert.ToDouble(ev.Element(xmlns + "Point").Element(xmlns + "lat").Value),
Longitude = Convert.ToDouble(ev.Element(xmlns + "Point").Element(xmlns + "long").Value),
};
this.PushPins = new ObservableCollection<SItem2>();
foreach (var ev in events)
{
var pushPin = new SItem2(ev.Latitude, ev.Longitude);
//Location = new GeoCoordinate(ev.Latitude, ev.Longitude )
this.PushPins.Add(pushPin);
}
}
Other class:
namespace observable_collection_test
{
public class SItem2
{
public double Latitude
{ get; set; }
public double Longitude
{ get; set; }
public SItem2(double Latitude, double Longitude)
{
this.Latitude = Latitude;
this.Longitude = Longitude;
}
public Location Location { get; set; }
}
}
XAML:
<my:Map ZoomBarVisibility="Visible" ZoomLevel="10" CredentialsProvider="xxxxx" Height="508" HorizontalAlignment="Left" Margin="0,22,0,0" Name="map1" VerticalAlignment="Top" Width="456" ScaleVisibility="Visible">
<my:MapItemsControl ItemsSource="{Binding PushPins}" >
<my:MapItemsControl.ItemTemplate>
<DataTemplate>
<my:Pushpin Background="Aqua" Location="{Binding Location}" ManipulationCompleted="pin_click">
</my:Pushpin></DataTemplate>
</my:MapItemsControl.ItemTemplate>
</my:MapItemsControl>
</my:Map>
You're trying to bind to a private field, _PushPins, instead of the public property PushPins. Also don't forget to implement INotifyPropertyChanged if you're changing the collection after binding.
I would do two things - firstly, implemented INotifyPropertyChanged and have your PushPins property use a private backing field. In the getter, just return the field value, in the setter, update the field value and invoke the PropertyChanged event.
Then, in your loop, rather than the getItems method (I would use PascalCase for method names) creating a local ObservableCollection, instantiate the PushPins collection and populate it directly.
private ObservableCollectin<SItem2> pushPins;
public ObservableCollection<SItem2> PushPins
{
get { return this.pushPins; }
set
{
this.pushPins = value;
this.OnPropertyChanged("PushPins");
}
}
public void GetItems()
{
...
this.PushPins = new ObservableCollection<SItem2>();
foreach (var ev in events)
{
var pushPin = new SItem2(ev.Latitude, ev.Longitude);
this.PushPins.Add(pushPin);
}
}
Populate the SItem2 Location property in the SItem2 constructor instead using the lat/long, and as Martin says, if you want the UI to update when you change the value of an SItem2 instance in the collection, then implement INotifyPropertyChanged on SItem2's properties also.