有没有办法以编程方式检查 Entity Framework Core 中的待定模型更改？

Posted 2023-04-12

【中文标题】有没有办法以编程方式检查 Entity Framework Core 中的待定模型更改？

【英文标题】：Is there a way to programmatically check pending model changes in Entity Framework Core?

【发布时间】：2020-06-26 08:25:33

【问题描述】：

我目前正在为 ASP.NET Core WebAPI 开发设置团队环境，使用 xUnit 和 GitLab CI 进行单元测试。对于数据库通信，我们使用 EF Core。

对于 EF Core，我们将使用 Code First 迁移，我们担心开发人员可能只会更新模型，而不会为他们的模型更改创建迁移。 因此，我们希望我们的 CI 运行代码库中存在的所有迁移，将它们与代码优先模型的当前状态进行比较，并在代码优先模型状态不等于运行所有迁移所产生的状态时失败。

有没有办法做到这一点？我在 EF Core 文档中找不到任何关于此的内容。

【问题讨论】：

AFAIK 无法在代码中比较模型状态，但您可以使用 CLI 生成 SQL 命令并进行比较？不是那种干净，但你有一个基本的比较。

我在这里有一些代码可以做到这一点：github.com/ErikEJ/EFCorePowerTools/blob/master/src/GUI/efpt/… - 但为什么不首先考虑数据库呢？

@ErikEJ 因为 EF Core 不首先支持数据库，并且迁移提供了很多好处。感谢您的示例代码，我会检查一下:)。

@hyvte 感谢您的建议，我确实想到了这一点，但我更喜欢更“干净”的方法。

EF Core 优先支持数据库！

【参考方案1】：

如果您使用的是 EF (core) 5，则需要稍微不同的版本（也改编自 @ErikEJ sample code）

    [Fact]
    public void ModelDoesNotContainPendingChanges()
    
        // Do not use the test database, the SQL Server model provider must be
        // used as that is the model provider that is used for scaffolding migrations.
        using var ctx = new DataContext(
            new DbContextOptionsBuilder<DataContext>()
                .UseNpgsql(DummyConnectionString)
                .Options);

        var modelDiffer = ctx.GetService<IMigrationsModelDiffer>();
        var migrationsAssembly = ctx.GetService<IMigrationsAssembly>();

        var dependencies = ctx.GetService<ProviderConventionSetBuilderDependencies>();
        var relationalDependencies = ctx.GetService<RelationalConventionSetBuilderDependencies>();

        var typeMappingConvention = new TypeMappingConvention(dependencies);
        typeMappingConvention.ProcessModelFinalizing(((IConventionModel)migrationsAssembly.ModelSnapshot.Model).Builder, null);

        var relationalModelConvention = new RelationalModelConvention(dependencies, relationalDependencies);
        var sourceModel = relationalModelConvention.ProcessModelFinalized(migrationsAssembly.ModelSnapshot.Model);

        var finalSourceModel = ((IMutableModel)sourceModel).FinalizeModel().GetRelationalModel();
        var finalTargetModel = ctx.Model.GetRelationalModel();

        var hasDifferences = modelDiffer.HasDifferences(finalSourceModel, finalTargetModel);
        if(hasDifferences)
        
            var changes = modelDiffer.GetDifferences(finalSourceModel, finalTargetModel);
            Assert.True(false, $"changes.Count changes between migrations and model. Debug this test for more details");
        

        Assert.False( hasDifferences );
    

【讨论】：

如何将其迁移到 EF Core 6？

【参考方案2】：

对于 EF Core 6，来自 @ErikEJ 的优秀 EF Core Power Tools：

var migrationsAssembly = _ctx.GetService<IMigrationsAssembly>();

var hasDifferences = false;
if (migrationsAssembly.ModelSnapshot != null) 
    var snapshotModel = migrationsAssembly.ModelSnapshot?.Model;

    if (snapshotModel is IMutableModel mutableModel) 
        snapshotModel = mutableModel.FinalizeModel();
    

    snapshotModel = _ctx.GetService<IModelRuntimeInitializer>().Initialize(snapshotModel);
    hasDifferences = _ctx.GetService<IMigrationsModelDiffer>().HasDifferences(
        snapshotModel.GetRelationalModel(),
        _ctx.GetService<IDesignTimeModel>().Model.GetRelationalModel());

https://github.com/ErikEJ/EFCorePowerTools/blob/5a16c37c59be854605f3e81d3131011d96c96704/src/GUI/efpt30.core/EFCoreMigrationsBuilder.cs#L98

【参考方案3】：

感谢@ErikEJ 的示例代码，我能够编写以下测试，完全符合我的要求：

    using FluentAssertions;
    using Microsoft.EntityFrameworkCore;
    using Microsoft.EntityFrameworkCore.Infrastructure;
    using Microsoft.EntityFrameworkCore.Migrations;
    using Xunit;

    /// <summary>
    /// Contains a test that verifies that the
    /// model does not contain any changes that are not included
    /// in the migrations.
    /// </summary>
    public class NoPendingModelChangesTest
    
        private static readonly string DummyConnectionString = @"Server=localhost;Database=DoesNotExist;Trusted_Connection=True;";

        /// <summary>
        /// Tests that the current model does not contain any changes
        /// that are not contained in the database migrators.
        /// In other words: tests that the current model state equals the
        /// state that results from all the migrations combined.
        /// </summary>
        [Fact]
        public void ModelDoesNotContainPendingChanges()
        
            // Do not use the test database, the SQL Server model provider must be
            // used as that is the model provider that is used for scaffolding migrations.
            using var ctx = new MyDatabase(
                new DbContextOptionsBuilder<MyDatabase>()
                    .UseSqlServer(DummyConnectionString)
                    .Options);

            var modelDiffer = ctx.GetService<IMigrationsModelDiffer>();
            var migrationsAssembly = ctx.GetService<IMigrationsAssembly>();

            var pendingModelChanges = modelDiffer
                .GetDifferences(
                    migrationsAssembly.ModelSnapshot?.Model,
                    ctx.Model);

            pendingModelChanges
                .Should()
                .BeEmpty(
                    because:
                        "the current model state should be equal to the state that results from all the migrations combined (try scaffolding a migration)");