How to refresh the database connection in WPF with Entity framework having Oracle database in MVVM?

Question

I have a WPF with Entity framework having Oracle database also follows MVVM pattern. So I need to create a link such a way that if on click the link that refresh the database connection means need to reconnect to the database. Please help me for this.

Answer 1

Why do you think you to to? See https://learn.microsoft.com/en-us/ef/core/dbcontext-configuration/

Answer 2

Hi,@ SANTHOSH B. Welcome to Microsoft Q&A.

You could try to see if DbEntityEntry.Reload Method is what you want.

Or refreshing data after fetching:

private void RefreshData(DBEntity entity)
{
    if (entity == null) return;

    ((IObjectContextAdapter)DbContext).ObjectContext.RefreshAsync(RefreshMode.StoreWins, entity);
}

private void RefreshData(List<DBEntity> entities)
{
    if (entities == null || entities.Count == 0) return;

    ((IObjectContextAdapter)DbContext).ObjectContext.RefreshAsync(RefreshMode.StoreWins, entities);
}

Additionally, you can see if the following example fits your needs.

Here is a simplified example that demonstrates the steps to refresh a database connection in a WPF application using Entity Framework involving an Oracle database in MVVM pattern.

App.config:

<configuration>
  <connectionStrings>
    <add name="OracleDbContext" 
         connectionString="Data Source=YourInitialDataSource;User Id=YourInitialUserId;Password=YourInitialPassword;" 
         providerName="..." />
  </connectionStrings>
</configuration>

DbContext:

using System.Data.Entity;

public class OracleDbContext : DbContext
{
    public OracleDbContext(string connectionString) : base(connectionString)
    {
    }

    public DbSet<Customer> Customers { get; set; }
    // ... other DbSet properties and configurations
}

ViewModelBase:

using System.ComponentModel;

public class ViewModelBase : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void OnPropertyChanged(string propertyName)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

MainViewModel:

public class MainViewModel : ViewModelBase
{

private OracleDbContext dbContext;

public MainViewModel()
{
    // Initialize DbContext with the default connection string
    dbContext = new OracleDbContext("OracleDbContext");
}

public void RefreshDatabaseConnection()
{
    // Get the new connection string (for simplicity, assuming it's hard-coded here)
    string newConnectionString = "Data Source=YourNewDataSource;User Id=YourNewUserId;Password=YourNewPassword;";

    // Dispose the existing DbContext
    dbContext.Dispose();

    // Initialize a new DbContext with the updated connection string
    dbContext = new OracleDbContext(newConnectionString);

    // Notify UI elements that depend on the DbContext to refresh
    OnPropertyChanged(nameof(CustomerData));
}

public IEnumerable<Customer> CustomerData => dbContext.Customers.ToList();
// ... other ViewModel logic
}

MainWindow.xaml:

<Window x:Class="YourNamespace.MainWindow"
       ...
        Title="MainWindow" Height="350" Width="525">
   <Window.DataContext>
        <local:MainViewModel/>
    </Window.DataContext>

    <Grid>
        <DataGrid ItemsSource="{Binding CustomerData}" AutoGenerateColumns="True"/>
        <Button Content="Refresh Connection" Command="{Binding RefreshCommand}" VerticalAlignment="Top" HorizontalAlignment="Left" Margin="10"/>
    </Grid>
</Window>

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Answer 3

I have a Oracle19c database is connected to 4 machines having WPF applications with MVVM pattern and follows entity frame work. So from this following query
SELECT MACHINE FROM v$session WHERE USERNAME = 'C##SAN' AND STATUS = 'ACTIVE';

and also using different parameters able to the other information.

Need to create a link by clicking the link the database connection for all the machines should refresh. How can I achieve . Please help me for this.