WPF How can I implement the INotifyPropertyChanged in a Three-tier architecture?

Question

I am a student and I am confused on using the INotifyPropertyChanged in a three-tier style of coding. Can you guys help me a bit with these?
I have a solution named MetroAppProject. It is composed of four projects (I omitted the using clauses and references, just imagine they are there and are working fine):
1. MetroApp.BluePrints - a class library composed of the classes in my sql db
An example of my class
namespace MetroApp.BluePrints
    public partial class Patient
        public long Id { get; set; }
        public string PatientNumber { get; set; }
        public string LastName { get; set; }
        public string FirstName { get; set; }
        public string MiddleName { get; set; }        
        public string AddressLine1 { get; set; }
        public Nullable<short> CityId { get; set; }
public string CityName { get; set; }
        public Nullable<short> ProvinceId { get; set; }
public string ProvinceName { get; set; }        
Then the second project:
2. MetroApp.DataAccess = a class library composed of methods that calls my sql procedures. I used the SqlHelper class which contains the connection strings and other stuffs.
example class
namespace MetroApp.DataAccess
    public class PatientDb
public Patient Retrieve(PatientParams parameters)
            SqlCommand command = new SqlCommand();
            Patient singItem = new Patient();
            command.CommandText = "RetrievePatients";
            command.CommandType = CommandType.StoredProcedure;
            command.Parameters.AddWithValue("@Id", parameters.Id).Direction = ParameterDirection.Input;
            DataTable dt = SqlHelper.GetData(command);
            if (dt.Rows.Count > 0)
                DataRow row = dt.Rows[0];
                singItem.Id = TDefaultValue.GetInt(row["Id"].ToString());
                singItem.PatientNumber = TDefaultValue.GetString(row["PatientNumber"].ToString());
                singItem.LastName = TDefaultValue.GetString(row["LastName"].ToString());
                singItem.FirstName = TDefaultValue.GetString(row["FirstName"].ToString());
                singItem.MiddleName = TDefaultValue.GetString(row["MiddleName"].ToString());
                singItem.AddressLine1 = TDefaultValue.GetString(row["AddressLine1"].ToString());
                singItem.CityId = TDefaultValue.GetShort(row["CityId"].ToString());
                singItem.CityName = TDefaultValue.GetString(row["CityName"].ToString());
                singItem.ProvinceId = TDefaultValue.GetShort(row["ProvinceId"].ToString());
                singItem.ProvinceName = TDefaultValue.GetString(row["ProvinceName"].ToString());
            return singItem;
        public List<Patient> RetrieveMany(PatientParams parameters)
            var items = new List<Patient>();
            var command = new SqlCommand();
            command.CommandText = "RetrievePatients";
            command.CommandType = CommandType.StoredProcedure;
            command.Parameters.AddWithValue("@Id", parameters.Id).Direction = ParameterDirection.Input;
            command.Parameters.AddWithValue("@PatientNumber", parameters.PatientNumber).Direction = ParameterDirection.Input;
            command.Parameters.AddWithValue("@LastName", parameters.LastName).Direction = ParameterDirection.Input;
            command.Parameters.AddWithValue("@FirstName", parameters.FirstName).Direction = ParameterDirection.Input;
            command.Parameters.AddWithValue("@MiddleName", parameters.MiddleName).Direction = ParameterDirection.Input;            
            command.Parameters.AddWithValue("@CityId", parameters.CityId).Direction = ParameterDirection.Input;
            command.Parameters.AddWithValue("@ProvinceId", parameters.ProvinceId).Direction = ParameterDirection.Input;
            DataTable dt = SqlHelper.GetData(command);
            foreach (DataRow row in dt.Rows)
                var item = new Patient();
                item.Id = TDefaultValue.GetLong(row["Id"].ToString());
                item.PatientNumber = (row["PatientNumber"].ToString());
                item.LastName = (row["LastName"].ToString());
                item.FirstName = (row["FirstName"].ToString());
                item.MiddleName = (row["MiddleName"].ToString());                
                item.AddressLine1 = (row["AddressLine1"].ToString());
                item.CityId = (short)row["CityId"].ToString();
                item.CityName = (row["CityName"].ToString());
                item.ProvinceId = (short)row["ProvinceId"].ToString();
                item.ProvinceName = (row["ProvinceName"].ToString());
                items.Add(item);
            return items;
        public bool Insert(Patient entity, int userId, ref bool doesExist)
            var command = new SqlCommand();
            try
                command.CommandText = "AddPatient";
                command.CommandType = CommandType.StoredProcedure;
                command.Parameters.AddWithValue("@PatientNumber", entity.PatientNumber).Direction = ParameterDirection.Input;
                command.Parameters.AddWithValue("@LastName", entity.LastName).Direction = ParameterDirection.Input;
                command.Parameters.AddWithValue("@FirstName", entity.FirstName).Direction = ParameterDirection.Input;
                command.Parameters.AddWithValue("@MiddleName", entity.MiddleName).Direction = ParameterDirection.Input;
                command.Parameters.AddWithValue("@AddressLine1", entity.AddressLine1).Direction = ParameterDirection.Input;
                command.Parameters.AddWithValue("@CityId", entity.CityId).Direction = ParameterDirection.Input;
                command.Parameters.AddWithValue("@ProvinceId", entity.ProvinceId).Direction = ParameterDirection.Input;
command.Parameters.AddWithValue("@Id", entity.Id).Direction = ParameterDirection.Input;
                command.Parameters.Add("@DoesExist", SqlDbType.Bit).Direction = ParameterDirection.Output;
                int result = SqlHelper.ExecuteNonQuery(command);
                doesExist = (bool)(command.Parameters["@DoesExist"].Value);
                entity.Id = (int)(command.Parameters["@Id"].Value);
                if (result == 0 || doesExist)
                    return false;
                return true;
            catch (Exception)
                return false;
        public bool Update(Patient entity, int userId, ref bool doesExist)
            var command = new SqlCommand();
            try
                command.CommandText = "EditPatient";
                command.CommandType = CommandType.StoredProcedure;
                command.Parameters.AddWithValue("@PatientNumber", entity.PatientNumber).Direction = ParameterDirection.Input;
                command.Parameters.AddWithValue("@LastName", entity.LastName).Direction = ParameterDirection.Input;
                command.Parameters.AddWithValue("@FirstName", entity.FirstName).Direction = ParameterDirection.Input;
                command.Parameters.AddWithValue("@MiddleName", entity.MiddleName).Direction = ParameterDirection.Input;
                command.Parameters.AddWithValue("@AddressLine1", entity.AddressLine1).Direction = ParameterDirection.Input;
                command.Parameters.AddWithValue("@CityId", entity.CityId).Direction = ParameterDirection.Input;
                command.Parameters.AddWithValue("@ProvinceId", entity.ProvinceId).Direction = ParameterDirection.Input;
command.Parameters.AddWithValue("@Id", SqlDbType.Int).Direction = ParameterDirection.Output;
                command.Parameters.Add("@DoesExist", SqlDbType.Bit).Direction = ParameterDirection.Output;
doesExist = (bool)(command.Parameters["@DoesExist"].Value);
                int result = SqlHelper.ExecuteNonQuery(command);
                if (result == 0 || doesExist)
                    return false;
                return true;
            catch (Exception)
                return false;
Then a business logic
3. MetroApp.BusinessLogic = class libray for calling the methods from DataAccess
namespace MetroApp.BusinessLogic
    public class PatientMgr
        #region Fields
        private readonly PatientDb _db;
        #endregion
        #region Properties
        public Patient Entity { get; set; }
        public List<Patient> EntityList { get; set; }
        public PatientParams Parameters { get; set; }
        #endregion
        #region Constructors
        public PatientMgr()
            _db = new PatientDb();
            Entity = new Patient();
            EntityList = new List<Patient>();
            Parameters = new PatientParams();
        #endregion
        #region Methods
public Patient Retrieve(PatientParams parameters)
            return _db.Retrieve(parameters);
        public List<Patient> RetrieveMany(PatientParams parameters)
            return _db.RetrieveMany(parameters);
        public bool Insert(Patient entity, int userId, ref bool doesExist)
            return _db.Insert(entity, userId, ref doesExist);
        public bool Update(Patient entity, int userId, ref bool doesExist)
            return _db.Update(entity, userId, ref doesExist);
        #endregion
Then the last one, the WPF GUI
<UserControl x:Class="MetroDentProject.Pages.PatientDetailsPage"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:dims="clr-namespace:MetroAppProject.UserCons"
             mc:Ignorable="d" 
             d:DesignHeight="720" d:DesignWidth="1280">
    <Grid x:Name="MainGrid" >
        <Grid.RowDefinitions>
            <RowDefinition  Height="40"/>
            <RowDefinition  />
            <RowDefinition  />
            <RowDefinition  />
            <RowDefinition  />
            <RowDefinition  />
            <RowDefinition  />
            <RowDefinition  />
            <RowDefinition  />
            <RowDefinition  />
            <RowDefinition  />
            <RowDefinition  />
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition />
            <ColumnDefinition />
            <ColumnDefinition />
        </Grid.ColumnDefinitions>
        <GroupBox Grid.Column="0" Grid.Row="1" Grid.RowSpan="7" x:Name="DetailsGroupBox" Header="Patient Details" >
            <Grid>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition/>
                    <ColumnDefinition/>
                </Grid.ColumnDefinitions>
                <Grid.RowDefinitions>
                    <RowDefinition/>
                    <RowDefinition/>
                    <RowDefinition/>
                    <RowDefinition/>
                    <RowDefinition/>
                    <RowDefinition/>
                    <RowDefinition/>
                    <RowDefinition/>
                    <RowDefinition/>
                    <RowDefinition/>
                </Grid.RowDefinitions>
                <TextBlock Text="Id: " Grid.Column="1" Grid.Row="0" Visibility="Collapsed"/>
                <TextBox x:Name="IdTextBox" Grid.Column="1" Grid.Row="1" Visibility="Collapsed"/>
                <TextBlock x:Name="PatientNumberTextBlock" Text="Patient Number: " Grid.Column="0" Grid.Row="0" />
                <TextBox x:Name="PatientNumberTextBox" Grid.Column="1" Grid.Row="0" IsReadOnly="True" IsReadOnlyCaretVisible="True"/>
                <TextBlock Text="Last Name: " Grid.Column="0" Grid.Row="1" />
                <TextBox x:Name="LastNameTextBox" Grid.Column="1" Grid.Row="1" />
                <TextBlock Text="First Name: " Grid.Column="0" Grid.Row="2" />
                <TextBox x:Name="FirstNameTextBox" Grid.Column="1" Grid.Row="2" />
                <TextBlock Text="Middle Name: " Grid.Column="0" Grid.Row="3" />
                <TextBox x:Name="MiddleNameTextBox" Grid.Column="1" Grid.Row="3" />
            </Grid>
        </GroupBox>
        <GroupBox x:Name="ContactDetailsGroupBox" Header="Contact Details" Grid.Column="1" Grid.Row="1" Grid.RowSpan="7">
            <Grid>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition/>
                    <ColumnDefinition />
                </Grid.ColumnDefinitions>
                <Grid.RowDefinitions>
                    <RowDefinition/>
                    <RowDefinition/>
                    <RowDefinition/>
                    <RowDefinition/>
                    <RowDefinition/>
                    <RowDefinition/>
                    <RowDefinition/>
                    <RowDefinition/>
                    <RowDefinition/>
                    <RowDefinition/>
                </Grid.RowDefinitions>
                <TextBlock Text="Address: " Grid.Column="0" Grid.Row="0" Grid.RowSpan="2" />
                <TextBlock Text="City: " Grid.Column="0" Grid.Row="2" />
                <TextBlock Text="Province: " Grid.Column="0" Grid.Row="3"/>
                <TextBox x:Name="AddressTextBox" Grid.Column="1" Grid.Row="0" Grid.RowSpan="2"
                         TextWrapping="Wrap"
                         AcceptsReturn="True"
                         VerticalScrollBarVisibility="Auto"
                         />
                <ComboBox x:Name="CitiesComboBox"  Grid.Column="1" Grid.Row="2"  />
                <ComboBox x:Name="ProvincesComboBox"  Grid.Column="1" Grid.Row="3" />
            </Grid>
        </GroupBox>
        <dims:FunctionButtonsControl x:Name="FunctionButtonsCon" Grid.Row="9" Grid.Column="0" Grid.ColumnSpan="2"
                                     ExecuteClick="FunctionButtonsCon_OnExecuteClick"
                                     UndoClick="FunctionButtonsCon_OnUndoClick"
                                     BackClick="FunctionButtonsCon_OnBackClick"
                                     DeleteClick="FunctionButtonsCon_OnDeleteClick"
                                     />
    </Grid>
</UserControl>
I apologize for the long post. As you can see, I don't use binding. Binding requires me to use INotifyPropertyChanged interface which I am not familiar. Can you at least make my project to implement the INotifypropertyChanged?
Here is my sample code for the WPF page:
public partial class PatientDetailsPage 
        readonly PatientMgr itemMgr = new PatientMgr();       
        public PatientParams CurrentPar = new PatientParams(); // for undoActionType _action = ActionType.Insert; // this is an enum from another project, ActionType.Insert, ActionType.Update
        public ActionType Action
            get { return _action; }
            set { _action = value; }
        public PatientDetailsPage()
            InitializeComponent();
            BindComboBoxes();
        #region Methods
        public void OnFragmentNavigation(FragmentNavigationEventArgs e)
        public void OnNavigatedFrom(NavigationEventArgs e)
        public void OnNavigatedTo(NavigationEventArgs e)
        {            Setup();
        public void OnNavigatingFrom(NavigatingCancelEventArgs e)
        public Patient GetPageEntity()
            Patient setEntity = new Patient();
            setEntity.Id = (long)IdTextBox.Text;
            setEntity.PatientNumber = PatientNumberTextBox.Text;
            setEntity.LastName = LastNameTextBox.Text;
            setEntity.FirstName = FirstNameTextBox.Text;
            setEntity.MiddleName = MiddleNameTextBox.Text;
            setEntity.AddressLine1 = AddressTextBox.Text;
            setEntity.CityId = (short)CitiesComboBox.SelectedValue);
            setEntity.ProvinceId = (short)ProvincesComboBox.SelectedValue;
            setEntity.StatusId = true;
            return setEntity;
        public void Setup()
            switch (Action)
                case ActionType.Insert:
                    Clearer(); //clears all textboxes and set all comboboxes to default
                    this.PatientNumberTextBlock.Visibility = Visibility.Collapsed;
                    this.PatientNumberTextBox.Visibility = Visibility.Collapsed;
                    FunctionButtonsCon.ExecuteButton.Content = "Add";
                    FunctionButtonsCon.DeleteButton.IsEnabled = false;
                    FunctionButtonsCon.DeleteButton.Visibility = Visibility.Hidden;
                    break;
                //**Setup Update
                case ActionType.Update:CurrentPar.Id = (long)IdTextBox.Text;
                    LoadSingle(CurrentPar);
                    this.PatientNumberTextBlock.Visibility = Visibility.Visible;
                    this.PatientNumberTextBox.Visibility = Visibility.Visible;
                    FunctionButtonsCon.ExecuteButton.Content = "Save";
                    FunctionButtonsCon.DeleteButton.IsEnabled = true;
                    FunctionButtonsCon.DeleteButton.Visibility = Visibility.Visible;
                    break;                
            LastNameTextBox.CaretIndex = LastNameTextBox.Text.Length;
            IsVisibleChanged += AutoFocus;
        public void LoadSingle(PatientParams parameters)
            var entity = itemMgr.Retrieve(parameters); //calls the BusinessLogic
            IdTextBox.Text = (entity.Id);
            PatientNumberTextBox.Text = (entity.PatientNumber);
            LastNameTextBox.Text = (entity.LastName);
            FirstNameTextBox.Text = (entity.FirstName);
            MiddleNameTextBox.Text = (entity.MiddleName);
            AddressTextBox.Text = (entity.AddressLine1);
            CitiesComboBox.SelectedValue = (short)entity.CityId;
            ProvincesComboBox.SelectedValue = (short)entity.ProvinceId;
        public void Save(ActionType action, int userId)
            itemMgr.Entity = GetPageEntity();
            bool doesExist = false;
            switch (action)
                case ActionType.Insert:
                    if (itemMgr.Insert((itemMgr.Entity), userId, ref doesExist))
                        System.Windows.Forms.MessageBox.Show("Successfully added a Patient!", "Patient Insertion");                  
                    else if (doesExist)
                        System.Windows.Forms.MessageBox.Show("Item already exists.", "Patient Insertion");
                    else
                        System.Windows.Forms.MessageBox.Show("Not all fields were filled in.", "Patient Insertion");
                    break;
                case ActionType.Update:
                    if (itemMgr.Update(itemMgr.Entity, userId, ref doesExist))
                        System.Windows.Forms.MessageBox.Show("Successfully updated a Patient!", "Patient Modification");
                        itemMgr.Parameters.Id = itemMgr.Entity.Id;
                        Action = ActionType.Update;
                        Setup();
                    else if (doesExist)
                        System.Windows.Forms.MessageBox.Show("Item already exists.", "Patient Modification");
                    else
                        System.Windows.Forms.MessageBox.Show("Not all fields were filled in.", "Patient Modification");
                    break;                
        public void Clearer()
            IdTextBox.Clear();
            PatientNumberTextBox.Clear();
            LastNameTextBox.Clear();
            FirstNameTextBox.Clear();
            MiddleNameTextBox.Clear();
            CitiesComboBox.SelectedIndex = 0;
            ProvincesComboBox.SelectedIndex = 0;
            AddressTextBox.Clear();            
        public void BindComboBoxes()
            CitiesComboBox.ItemsSource = new BindingSource(CommonMgr.GetCitiesDropDown(), null);// the CommonMgr is a static class from another project. It works just fine
            CitiesComboBox.DisplayMemberPath = "Value";
            CitiesComboBox.SelectedValuePath = "Key";           
            ProvincesComboBox.ItemsSource = new BindingSource(CommonMgr.GetProvincesDropDown(), null);
            ProvincesComboBox.DisplayMemberPath = "Value";
            ProvincesComboBox.SelectedValuePath = "Key";
            CitiesComboBox.SelectedIndex = 0;
            ProvincesComboBox.SelectedIndex = 0;
        #endregion
        #region Events
        private void FunctionButtonsCon_OnExecuteClick(object sender, RoutedEventArgs e)
            Save(Action, SessionHelper.MyUser.Id); //SessionHelper.MyUser.Id
        private void FunctionButtonsCon_OnUndoClick(object sender, RoutedEventArgs e)
            if (Action == ActionType.Insert)
                Clearer();
                return;
        private void FunctionButtonsCon_OnBackClick(object sender, RoutedEventArgs e)
            Exiter();
        private void FunctionButtonsCon_OnDeleteClick(object sender, RoutedEventArgs e)
            var ans = System.Windows.Forms.MessageBox.Show("Are you sure you want to delete this entry?", "Patient Deletion", MessageBoxButtons.YesNo);
            if (!Equals(ans, System.Windows.Forms.DialogResult.Yes)) return;
            Action = ActionType.Delete;
            Save(Action, SessionHelper.MyUser.Id);
            Exiter();
        #endregion

Answer 1

Hello Kokombads,
I thought you are using MVVM from your title but it seems your project is just a simple WPF project. In that way, please check the following msdn article to know how to Implement Property Change Notification
https://msdn.microsoft.com/en-us/library/ms743695(v=vs.110).aspx
using System.ComponentModel;
namespace SDKSample
// This class implements INotifyPropertyChanged
// to support one-way and two-way bindings
// (such that the UI element updates when the source
// has been changed dynamically)
public class Person : INotifyPropertyChanged
private string name;
// Declare the event
public event PropertyChangedEventHandler PropertyChanged;
public Person()
public Person(string value)
this.name = value;
public string PersonName
get { return name; }
set
name = value;
// Call OnPropertyChanged whenever the property is updated
OnPropertyChanged("PersonName");
// Create the OnPropertyChanged method to raise the event
protected void OnPropertyChanged(string name)
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
handler(this, new PropertyChangedEventArgs(name));
It is not so complex, you only need to refer to the interface from here:
https://msdn.microsoft.com/en-us/library/system.componentmodel.inotifypropertychanged(v=vs.110).aspx
And understand that you have to do the following:
For change notification to occur in a binding between a bound client and a data source, your bound type should either:
Implement the INotifyPropertyChanged interface (preferred).
Provide a change event for each property of the bound type
Best regards,
Barry
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