過去幾周我一直在開發 .NET Core 6 控制臺應用程式（不是 ASP.NET），現在我嘗試實作 Entity Framework 6 遷移到它。
但是，即使我重用了使用遷移的作業資料庫模型中的一些代碼，但現在我無法讓它作業，而且由于缺乏來自dotnet-ef.
由于我不記得的原因，我重用了來自使用的 Design-Time DbContext creation 的代碼的資料庫專案。我不知道這是否是我進行遷移的最佳方式，但至少它設法在以前的專案中作業。IDesignTimeDbContextFactory<DbContext>我以與之前相同的方式實作了所需的介面：
public class MySqlContextFactory : IDesignTimeDbContextFactory<MySqlContext>
{
public MySqlContext CreateDbContext(string[] args)
{
DbContextOptionsBuilder optionsBuilder = new();
ServerVersion mariaDbVersion = new MariaDbServerVersion(new Version(10, 6, 5));
optionsBuilder.UseMySql(DatabaseCredentials.GetConnectionString(), mariaDbVersion);
return new MySqlContext();
}
}
public class MySqlContext : DbContext
{
public DbSet<Endpoint> EndpointsSet { get; set; }
private readonly string _connectionString;
public MySqlContext() : base()
=> _connectionString = DatabaseCredentials.GetConnectionString();
public MySqlContext(string connectionString) : base()
=> _connectionString = connectionString;
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
=> Configurator.Configure(optionsBuilder, _connectionString);
protected override void OnModelCreating(ModelBuilder modelBuilder)
=> Configurator.Create(modelBuilder);
}
public static void Configure(DbContextOptionsBuilder optionsBuilder, string connectionString)
{
ServerVersion mariaDbVersion = new MariaDbServerVersion(new Version(10, 6, 5));
optionsBuilder.UseMySql(connectionString, mariaDbVersion);
}
public static void Create(ModelBuilder modelBuilder)
{
IEnumerable<Type> types = ReflectionUtils.GetImplementedTypes(typeof(IEntityTypeConfiguration<>));
if (types.Any())
{
foreach (Type entityConfigurationType in types)
{
modelBuilder.ApplyConfigurationsFromAssembly(entityConfigurationType.Assembly);
}
}
else
{
Environment.Exit((int) EExitCodes.EF_MODEL_NOT_FOUND);
}
}
但是，當我嘗試創建第一個遷移時，我收到了來自 dotnet-ef 工具的絕對非描述性輸出的提示：
PS> dotnet ef migrations add Init
Build started...
Build succeeded.
PS>
但是我的專案沒有進行任何遷移，也沒有任何改變。--verbose所以我決定通過在 PS 命令上附加標志來強制 dotnet ef 告訴我更多資訊：
[...]
Build succeeded.
dotnet exec --depsfile F:\pablo\Documents\source\MyBot\bin\Debug\net6.0\MyBot.deps.json --additionalprobingpath C:\Users\pablo\.nuget\packages --runtimeconfig F:\pablo\Documents\source\MyBot\bin\Debug\net6.0\MyBot.runtimeconfig.json C:\Users\pablo\.dotnet\tools\.store\dotnet-ef\6.0.1\dotnet-ef\6.0.1\tools\netcoreapp3.1\any\tools\netcoreapp2.0\any\ef.dll migrations add Init -o Migrations\Init --assembly F:\pablo\Documents\source\MyBot\bin\Debug\net6.0\MyBot.dll --project F:\pablo\Documents\source\MyBot\MyBot.csproj --startup-assembly F:\pablo\Documents\source\MyBot\bin\Debug\net6.0\MyBot.dll --startup-project F:\pablo\Documents\source\MyBot\MyBot.csproj --project-dir F:\pablo\Documents\source\MyBot\ --root-namespace MyBot--language C# --framework net6.0 --nullable --working-dir F:\pablo\Documents\source\MyBot--verbose
Using assembly 'MyBot'.
Using startup assembly 'MyBot'.
Using application base 'F:\pablo\Documents\source\MyBot\bin\Debug\net6.0'.
Using working directory 'F:\pablo\Documents\source\MyBot'.
Using root namespace 'MyBot'.
Using project directory 'F:\pablo\Documents\source\MyBot\'.
Remaining arguments: .
Finding DbContext classes...
Finding IDesignTimeDbContextFactory implementations...
Found IDesignTimeDbContextFactory implementation 'MySqlContextFactory'.
Found DbContext 'MySqlContext'.
Finding application service provider in assembly 'MyBot'...
Finding Microsoft.Extensions.Hosting service provider...
No static method 'CreateHostBuilder(string[])' was found on class 'Program'.
No application service provider was found.
Finding DbContext classes in the project...
Using DbContext factory 'MySqlContextFactory'.
PS>
我認為我可以搜索的第一件事是CreateHostBuilder該工具正在搜索但不檢索的功能。然而，再一次，我能找到的所有檔案都是指 ASP.NET 應用程式，以及我沒有在我的機器人應用程式中實作的編程模式。我的應用程式確實通過定制的依賴注入檢索服務（也許這就是該行的原因No application service provider was found.？），但我沒有找到一種方法來實作該 CreateHostBuilder 函式而不更改所有內容。
Just for adding the information, this is how I managed to create and configure the EF model with the non-migrations approach:
public static IServiceProvider GetServices(DiscordSocketClient client, CommandService commands)
{
ServiceCollection services = new();
services.AddSingleton(client);
services.AddSingleton(commands);
services.AddSingleton<HttpClient>();
services.AddDbContext<MySqlContext>(ServiceLifetime.Scoped);
return AddServices(services) // builds service provider;
}
private static async Task InitDatabaseModel(IServiceProvider provider)
{
MySqlContext? dbCtxt = provider.GetService<MySqlContext>();
if (dbCtxt == null)
{
Environment.Exit((int) EExitCodes.DB_SERVICE_UNAVAILABLE);
}
await dbContext.Database.EnsureDeletedAsync();
await dbContext.Database.EnsureCreatedAsync();
}
But unfortunately, my application is planned to interact with a database dynamically, so the Code-First configuring approach is not valid for me.
How can I solve this? Is an approach problem, or am I messing around with the custom non ASP.NET Dependency Injection provider? Thank you all
uj5u.com熱心網友回復：
您的IDesignTimeDbContextFactory. EF Core 正在嘗試為您的這個工廠創建一個MySqlContext.
public class MySqlContextFactory : IDesignTimeDbContextFactory<MySqlContext>
{
public MySqlContext CreateDbContext(string[] args)
{
// set up options
DbContextOptionsBuilder optionsBuilder = new();
ServerVersion mariaDbVersion = new MariaDbServerVersion(new Version(10, 6, 5));
optionsBuilder.UseMySql(DatabaseCredentials.GetConnectionString(), mariaDbVersion);
// *** this is the issue ***
// return default constructor W/O options (ie, UseMySql is never called)
return new MySqlContext();
}
}
您可以將此建構式添加到您的DbContext類中：
public MySqlContext(DbContextOptions<MySqlContext> options)
: base(options)
{
}
然后 return new MySqlContext(optionsBuilder.Options)從你的工廠。
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