你的MigrationExtensions去哪了 about kurisu HOT 1 CLOSED

/// <summary>
/// 动态迁移
/// </summary>
/// <param name="dbContext"></param>
public static async Task RunDynamicMigrationAsync(this DbContext dbContext)
{
    IModel lastModel = null;
    var now = DateTime.Now;

    if (await dbContext.Database.IsTableExistsAsync(dbContext.Model.FindEntityType(typeof(AutoMigrationsHistory))!.GetTableName()))
    {
        // 读取迁移记录,还原modelSnapshot
        var lastMigration = dbContext.Set<AutoMigrationsHistory>()
            .AsNoTracking()
            .OrderByDescending(x => x.Id)
            .FirstOrDefault();

        if (!string.IsNullOrEmpty(lastMigration?.SnapshotDefine))
        {
            var snapshot = CreateModelSnapshot(FullName, lastMigration.SnapshotDefine);
            lastModel = snapshot.Model;
        }
    }

    var differ = dbContext.GetService<IMigrationsModelDiffer>();
    var lastRelationalModel = lastModel == null
        ? null
        : dbContext.GetService<IModelRuntimeInitializer>()
            .Initialize(((IMutableModel) lastModel).FinalizeModel())
            .GetRelationalModel();
    var currentRelationalModel = dbContext.GetService<IDesignTimeModel>().Model.GetRelationalModel();

    //判断是否存在更改
    if (differ.HasDifferences(lastRelationalModel, currentRelationalModel))
    {
        var operations = differ.GetDifferences(lastRelationalModel, currentRelationalModel);

        //执行迁移
        await dbContext.MigrationAsync(operations);

        //生成新的快照
        var snapshotCode = new DesignTimeServicesBuilder(typeof(DefaultAppDbContext).Assembly, Assembly.GetExecutingAssembly(), new OperationReporter(new OperationReportHandler()), Array.Empty<string>())
            .Build(dbContext)
            .GetRequiredService<IMigrationsCodeGenerator>()
            .GenerateSnapshot(Namespace, typeof(DefaultAppDbContext), ClassName, currentRelationalModel.Model);

        dbContext.Set<AutoMigrationsHistory>().Add(new AutoMigrationsHistory
        {
            SnapshotDefine = snapshotCode,
            MigrationTime = now
        });

        await dbContext.SaveChangesAsync();
    }
}


/// <summary>
/// 创建模型快照
/// </summary>
/// <param name="fullName"></param>
/// <param name="codeDefine"></param>
/// <returns></returns>
private static ModelSnapshot CreateModelSnapshot(string fullName, string codeDefine)
{
    var references = typeof(DefaultAppDbContext).Assembly
        .GetReferencedAssemblies()
        .Select(e => MetadataReference.CreateFromFile(Assembly.Load(e).Location))
        .Union(new MetadataReference[]
        {
            MetadataReference.CreateFromFile(Assembly.Load("netstandard").Location),
            MetadataReference.CreateFromFile(Assembly.Load("System.Runtime").Location),
            MetadataReference.CreateFromFile(typeof(object).Assembly.Location),
            MetadataReference.CreateFromFile(typeof(DefaultAppDbContext).Assembly.Location)
        });
    var compilation = CSharpCompilation.Create(Namespace)
        .WithOptions(new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary))
        .AddReferences(references)
        .AddSyntaxTrees(SyntaxFactory.ParseSyntaxTree(codeDefine));

    using var stream = new MemoryStream();
    var compileResult = compilation.Emit(stream);

    if (compileResult.Success)
    {
        var obj = Assembly.Load(stream.GetBuffer()).CreateInstance(fullName);
        return obj as ModelSnapshot;
    }

    return null;
}


/// <summary>
/// 迁移
/// </summary>
/// <param name="dbContext"></param>
/// <param name="operations"></param>
private static async Task MigrationAsync(this DbContext dbContext, IReadOnlyList<MigrationOperation> operations)
{
    var sqlGenerator = dbContext.GetService<IMigrationsSqlGenerator>();

    var list = sqlGenerator
        .Generate(operations, dbContext.Model)
        .Select(p => p.CommandText).ToList();

    await dbContext.Database.ExecuteSqlRawAsync(string.Join(Environment.NewLine, list));
}