Refactored to use postgres for production and sqlite for development

Program.cs

@@ -1,29 +1,58 @@
+using Example.Data;
 using Microsoft.AspNetCore.Identity;
 using Microsoft.EntityFrameworkCore;
-using Example.Data;
 
 var builder = WebApplication.CreateBuilder(args);
 
-// Add services to the container.
-var connectionString = builder.Configuration.GetConnectionString("DefaultConnection");
-builder.Services.AddDbContext<ApplicationDbContext>(options =>
-    options.UseSqlite(connectionString));
+var connectionString = builder.Configuration.GetConnectionString("DefaultConnection")
+    ?? throw new InvalidOperationException("Connection string 'DefaultConnection' was not found.");
+var configuredProvider = builder.Configuration["Database:Provider"]
+    ?? throw new InvalidOperationException("Database provider configuration 'Database:Provider' was not found.");
+
+if (builder.Environment.IsDevelopment())
+{
+    EnsureProviderMatchesEnvironment(configuredProvider, expectedProvider: "Sqlite", builder.Environment.EnvironmentName);
+    ValidateConnectionString(connectionString, configuredProvider);
+
+    builder.Services.AddDbContext<ApplicationDbContext, SqliteApplicationDbContext>(options =>
+        options.UseSqlite(connectionString));
+}
+else
+{
+    EnsureProviderMatchesEnvironment(configuredProvider, expectedProvider: "Postgres", builder.Environment.EnvironmentName);
+    ValidateConnectionString(connectionString, configuredProvider);
+
+    builder.Services.AddDbContext<ApplicationDbContext, PostgresApplicationDbContext>(options =>
+        options.UseNpgsql(connectionString));
+}
+
 builder.Services.AddDatabaseDeveloperPageExceptionFilter();
 
-builder.Services.AddDefaultIdentity<IdentityUser>(options => options.SignIn.RequireConfirmedAccount = true)
-    .AddEntityFrameworkStores<ApplicationDbContext>();
+var identityBuilder = builder.Services.AddDefaultIdentity<IdentityUser>(options => options.SignIn.RequireConfirmedAccount = true);
+if (builder.Environment.IsDevelopment())
+{
+    identityBuilder.AddEntityFrameworkStores<SqliteApplicationDbContext>();
+}
+else
+{
+    identityBuilder.AddEntityFrameworkStores<PostgresApplicationDbContext>();
+}
+
 builder.Services.AddControllersWithViews();
 
 var app = builder.Build();
 
-// Call the database initializer
 using (var services = app.Services.CreateScope())
 {
     var db = services.ServiceProvider.GetRequiredService<ApplicationDbContext>();
-    ApplicationDbInitializer.Initialize(db);
+    db.Database.Migrate();
+
+    if (app.Environment.IsDevelopment())
+    {
+        ApplicationDbInitializer.SeedDevelopmentData(db);
+    }
 }
 
-// Configure the HTTP request pipeline.
 if (app.Environment.IsDevelopment())
 {
     app.UseMigrationsEndPoint();
@@ -31,7 +60,6 @@ if (app.Environment.IsDevelopment())
 else
 {
     app.UseExceptionHandler("/Home/Error");
-    // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
     app.UseHsts();
 }
 
@@ -49,3 +77,42 @@ app.MapControllerRoute(
 app.MapRazorPages();
 
 app.Run();
+
+static void EnsureProviderMatchesEnvironment(string configuredProvider, string expectedProvider, string environmentName)
+{
+    if (!string.Equals(configuredProvider, expectedProvider, StringComparison.OrdinalIgnoreCase))
+    {
+        throw new InvalidOperationException(
+            $"Environment '{environmentName}' must use the '{expectedProvider}' database provider, but configuration specifies '{configuredProvider}'.");
+    }
+}
+
+static void ValidateConnectionString(string connectionString, string configuredProvider)
+{
+    if (string.Equals(configuredProvider, "Sqlite", StringComparison.OrdinalIgnoreCase))
+    {
+        if ((!connectionString.Contains("Data Source=", StringComparison.OrdinalIgnoreCase) &&
+             !connectionString.Contains("DataSource=", StringComparison.OrdinalIgnoreCase)) ||
+            connectionString.Contains("Host=", StringComparison.OrdinalIgnoreCase) ||
+            connectionString.Contains("Server=", StringComparison.OrdinalIgnoreCase))
+        {
+            throw new InvalidOperationException("The development connection string does not look like a valid SQLite connection string.");
+        }
+
+        return;
+    }
+
+    if (string.Equals(configuredProvider, "Postgres", StringComparison.OrdinalIgnoreCase))
+    {
+        if (!connectionString.Contains("Host=", StringComparison.OrdinalIgnoreCase) ||
+            connectionString.Contains("Server=", StringComparison.OrdinalIgnoreCase) ||
+            connectionString.Contains("DataSource=", StringComparison.OrdinalIgnoreCase))
+        {
+            throw new InvalidOperationException("The production connection string does not look like a valid PostgreSQL connection string.");
+        }
+
+        return;
+    }
+
+    throw new InvalidOperationException($"Unsupported database provider '{configuredProvider}'.");
+}