在Prism多模块WPF应用中如何修改EF6的数据库连接字符串？

Hey Joey, let's work through this EF6 + Prism WPF multi-module setup issue together. I’ve helped a few folks with similar structure problems, so here’s a step-by-step approach that should get you sorted:

First, stop scattering EF-related code across modules—this is the biggest source of pain in multi-module Prism apps. Instead, create a standalone class library project (e.g., YourApp.Data) to house all EF6 core components:

• DbContext Implementation: Place your main DbContext here, with DbSets for all entities across your modules:

  public class YourAppDbContext : DbContext
  {
      public YourAppDbContext() : base("YourAppConnectionString") { }
  
      // Add DbSets for entities from all modules
      public DbSet<Customer> Customers { get; set; }
      public DbSet<Order> Orders { get; set; }
  }
  

• Entity Classes: Move all your model entities here, or have module-specific entities reference this library (if you want to keep them in their modules, just ensure they’re accessible to the DbContext).
• Migration Management: Handle all EF migrations from this project. Open the Package Manager Console, set YourApp.Data as the default project, then run Enable-Migrations, Add-Migration, and Update-Database commands here exclusively.

Prism’s dependency injection (DI) system is your friend here—you don’t want modules creating their own DbContext instances (this causes connection leaks and cache conflicts).

• Register in Bootstrapper: In your Root module’s bootstrapper, register the DbContext as a singleton (safe for WPF desktop apps):

  protected override void ConfigureContainer()
  {
      base.ConfigureContainer();
      // Singleton lifetime ensures one shared DbContext instance
      Container.RegisterType<YourAppDbContext>(new ContainerControlledLifetimeManager());
  }
  

• Inject into Module ViewModels: In any module’s ViewModel, request the DbContext via constructor injection:

  public CustomerListViewModel(YourAppDbContext dbContext)
  {
      _dbContext = dbContext;
      // Use _dbContext to query or modify data
      LoadCustomersCommand = new DelegateCommand(LoadCustomers);
  }
  
  private void LoadCustomers()
  {
      Customers = _dbContext.Customers.ToObservableCollection();
  }
  

  Note: Make sure every module project references the YourApp.Data class library.

If your modules have unique entities, you don’t have to cram everything into the root data project:

• Use Entity Configuration Classes: Let modules define their own entity configurations, then load them in the central DbContext:

  protected override void OnModelCreating(DbModelBuilder modelBuilder)
  {
      // Load configurations from modules (use reflection or a registry pattern for scalability)
      modelBuilder.Configurations.Add(new CustomerConfiguration());
      modelBuilder.Configurations.Add(new OrderConfiguration());
      base.OnModelCreating(modelBuilder);
  }
  

• Keep Entities in Modules: If you prefer to keep entities in their respective modules, just mark them as public and ensure the YourApp.Data project references the module projects (or use a shared interfaces project for loose coupling).

• Don’t duplicate connection strings: The WPF app uses the startup project’s config file, so put your EF connection string in the Root module’s App.config:

  <connectionStrings>
    <add name="YourAppDbContext" 
         connectionString="Data Source=YOUR_SERVER;Initial Catalog=YOUR_DB;Integrated Security=True;" 
         providerName="System.Data.SqlClient" />
  </connectionStrings>
  

• Never new up a DbContext in modules: Always use DI to get instances—this ensures consistency and easier testing.
• Test incrementally: Start with one module and a simple entity, verify data loads correctly, then expand to other modules.

To validate everything works:

1. Add a test entity (e.g., TestItem) to YourApp.Data
2. Run Add-Migration AddTestItem and Update-Database
3. Inject YourAppDbContext into a module ViewModel, write a simple query to fetch TestItems
4. Bind the results to a ListBox in the View—if data loads without errors, your setup is solid.

If you hit specific errors (like DI resolution failures, migration errors, or data access exceptions), drop the details and I’ll help you troubleshoot further!

内容的提问来源于stack exchange，提问作者Joey Joystick