C# WPF ObservableCollection does not update Grid - wpf

Question

My implementation of an ObservableCollection does not update my Grid and I don't know why:
The first XAML-Window 'UserControlStaff.xaml' displays the Grid where the user data can be seen. The second XAML-Window allows to add users and is called 'CreateUser.xaml'.
The code behind the XAML-Windows is attached to this post as well.
My Code goes as follows:
[XAML] UserControlStaff.xaml
<UserControl x:Class="MyApp.UserControlStaff"
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"
mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="786">
<StackPanel x:Name="spStaff" Orientation="Vertical" Visibility="Visible">
<Button Background="Azure" Click="btnCreateUser_Click" HorizontalAlignment="Left" Width="786" Height="40">
<Bold>Mitarbeiter hinzufügen</Bold></Button>
<ScrollViewer MaxHeight="504">
<DataGrid Background="#DBDB72" ItemsSource="{Binding UserDataObject}" CanUserAddRows="false" Width="786" />
</ScrollViewer>
</StackPanel>
</UserControl>
[Code] UserControlStaff.xaml.cs
namespace MyApp
{
/// <summary>
/// Interaktionslogik für UserControlStaff.xaml
/// </summary>
public partial class UserControlStaff : UserControl
{
ObservableCollection<User> mUserDataObject = new ObservableCollection<User>();
public ObservableCollection<User> UserDataObject
{
get
{
return mUserDataObject;
}
}
public UserControlStaff()
{
InitializeComponent();
DataContext = this;
try
{
string connectionString = ConfigurationManager.ConnectionStrings["MyApp.Properties.Settings.ConString"].ConnectionString;
string queryString = string.Empty;
using (SqlConnection connection = new SqlConnection(connectionString))
{
queryString = "SELECT ID, username AS Username, Password AS Passwort, (SELECT role FROM Roles WHERE ID = t1.role) AS Rolle FROM Users t1 ORDER BY ID";
SqlCommand cmd = new SqlCommand(queryString, connection);
SqlDataAdapter sda = new SqlDataAdapter(cmd);
DataTable dt = new DataTable("Users");
sda.Fill(dt);
foreach (DataRow row in dt.Rows)
{
int pID = 0;
string pUsername = "";
string pPassword = "";
string pRole = "";
foreach (DataColumn col in dt.Columns)
{
if (col.ToString().Trim() == "ID")
{
pID = int.Parse(row[col].ToString());
}
else if (col.ToString().Trim() == "Username")
{
pUsername = row[col].ToString();
}
else if (col.ToString().Trim() == "Passwort")
{
pPassword = row[col].ToString();
}
else if (col.ToString().Trim() == "Rolle")
{
pRole = row[col].ToString();
}
}
// Show Users DB table in MainWindow
mUserDataObject.Add(new User { ID = pID, Username = pUsername, Password = pPassword, Role = pRole });
}
// Show Users DB table in MainWindow
//XAML Grid: Name="gridUsers"
//CS Code: gridUsers.DataContext = dt.DefaultView;
}
}
catch {
throw;
}
}
private void btnCreateUser_Click(object sender, RoutedEventArgs e)
{
CreateUser popup = new CreateUser();
popup.Show();
}
private void UpdateUserData()
{
// implement
}
private void DeleteUserData()
{
// implement
}
}
}
[XAML] CreateUser.xaml
<Window x:Class="MyApp.CreateUser"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Mitarbeiter hinzufügen" Height="300" Width="400">
<Grid>
<Label Content="Username" HorizontalAlignment="Left" Margin="10,44,0,0" VerticalAlignment="Top" Width="120" Height="30"/>
<Label Content="Passwort" HorizontalAlignment="Left" Margin="10,88,0,0" VerticalAlignment="Top" Width="120" Height="30"/>
<Label Content="Rolle" HorizontalAlignment="Left" Margin="10,132,0,0" VerticalAlignment="Top" Width="120" Height="30"/>
<TextBox HorizontalAlignment="Left" Height="30" Margin="150,44,0,0" TextWrapping="Wrap" Name="TextBoxUsername" Text="{Binding Path=Username}" VerticalAlignment="Top" Width="180"/>
<TextBox HorizontalAlignment="Left" Height="30" Margin="150,88,0,0" TextWrapping="Wrap" Name="TextBoxPassword" Text="{Binding Path=Password}" VerticalAlignment="Top" Width="180"/>
<ComboBox HorizontalAlignment="Left" Height="30" Margin="150,132,0,0" VerticalAlignment="Top" Width="180" Loaded="ComboBox_Loaded" SelectionChanged="ComboBox_SelectionChanged"/>
<Button Click="btnSaveUserData_Click" Content="Speichern" HorizontalAlignment="Left" Margin="217,219,0,0" VerticalAlignment="Top" Height="30" Width="75"/>
<Button Click="btnCloseWindow_Click" Content="Abbrechen" HorizontalAlignment="Left" Margin="297,219,0,0" VerticalAlignment="Top" Height="30" Width="75"/>
</Grid>
</Window>
[Code] CreateUser.xaml.cs
namespace MyApp
{
/// <summary>
/// Interaktionslogik für CreateUser.xaml
/// </summary>
public partial class CreateUser : Window
{
User userObject;
public CreateUser()
{
InitializeComponent();
this.userObject = new User();
}
private void ComboBox_Loaded(object sender, RoutedEventArgs e)
{
// ToDO: Rollenzuweisung automatisieren aus Datenbanktabelle MyApp.Roles
List<string> data = new List<string>();
data.Add("Chef");
data.Add("Restaurantmitarbeiter");
data.Add("Fahrer");
// ... Get the ComboBox reference.
var comboBox = sender as ComboBox;
// ... Assign the ItemsSource to the List.
comboBox.ItemsSource = data;
// ... Make the second item selected.
comboBox.SelectedIndex = 1;
}
private void ComboBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
// ... Get the ComboBox.
var comboBox = sender as ComboBox;
// ... Set SelectedItem as Window Title.
string value = comboBox.SelectedItem as string;
//this.Title = "Selected: " + value;
this.userObject.Role = value;
}
private void btnSaveUserData_Click(object sender, RoutedEventArgs e)
{
try
{
this.userObject.Username = TextBoxUsername.Text;
this.userObject.Password = TextBoxPassword.Text;
int UserRole;
// ToDO: Rollenzuweisung automatisieren aus Datenbanktabelle MyApp.Roles
if (this.userObject.Role == "Chef")
{
UserRole = 1;
}
else if (this.userObject.Role == "Restaurantmitarbeiter")
{
UserRole = 2;
}
else if (this.userObject.Role == "Fahrer")
{
UserRole = 3;
}
else
{
UserRole = 2; // Default UserRole is "Restaurantmitarbeiter"
}
if (this.userObject.Username.Trim() != "" && this.userObject.Password.Trim() != "")
{
CreateUserData(this.userObject.Username, this.userObject.Password, UserRole);
// ToDO: Update DataGrid in UserControlStaff
this.Close();
MessageBox.Show("Mitarbeiter hinzugefügt!");
} else {
MessageBox.Show("Bitte Username und Passwort eingeben.");
}
}
catch { throw; }
}
private void CreateUserData(string pUsername, string pPassword, int pRole)
{
string connectionString = ConfigurationManager.ConnectionStrings["MyApp.Properties.Settings.ConString"].ConnectionString;
string queryString = "INSERT INTO Users (ID, username, password, role) VALUES ((SELECT TOP 1 ID+1 FROM Users ORDER BY ID DESC), '" + pUsername + "', '" + pPassword + "', '" + pRole + "')";
SqlConnection connection = new SqlConnection(connectionString);
SqlCommand cmd = new SqlCommand(queryString, connection);
SqlDataAdapter sda = new SqlDataAdapter(cmd);
DataTable dt = new DataTable("Users");
sda.Fill(dt);
string UserRole;
if (pRole == 1)
{
UserRole = "Chef";
}
else if (pRole == 2)
{
UserRole = "Restaurantmitarbeiter";
}
else if (pRole == 3)
{
UserRole = "Fahrer";
}
else
{
UserRole = "Restaurantmitarbeiter"; // Default UserRole is "Restaurantmitarbeiter"
}
// Add to Observable Collection
// ToDO
// mUserDataObject.Add(new User { ID = pID, Username = pUsername, Password = pPassword, Role = pRole });
}
private void btnCloseWindow_Click(object sender, RoutedEventArgs e)
{
this.Close();
}
}
}