EF Core 7添加HasColumnName时触发NullReferenceException异常

使用EF Core 7.0.7搭配.NET 8，修改实体属性的列名配置后，执行数据库迁移时报空引用异常。

旧实体配置 #

builder.Property(c => c.AddressId).IsRequired();

新实体配置 #

builder.Property(c => c.AddressId).IsRequired().HasColumnName("addressId");

执行的迁移命令 #

dotnet ef migrations add UpdateFieldName
dotnet ef database update

报错信息 #

System.NullReferenceException: 对象引用未设置为对象的实例。

at MySql.EntityFrameworkCore.Migrations.MySQLMigrationsSqlGenerator.Generate(RenameColumnOperation operation, IModel model, MigrationCommandListBuilder builder)
at Microsoft.EntityFrameworkCore.Migrations.MigrationsSqlGenerator.<>c.<.cctor>b__82_22(MigrationsSqlGenerator g, MigrationOperation o, IModel m, MigrationCommandListBuilder b)
at Microsoft.EntityFrameworkCore.Migrations.MigrationsSqlGenerator.Generate(MigrationOperation operation, IModel model, MigrationCommandListBuilder builder)
at MySql.EntityFrameworkCore.Migrations.MySQLMigrationsSqlGenerator.Generate(MigrationOperation operation, IModel model, MigrationCommandListBuilder builder)
at Microsoft.EntityFrameworkCore.Migrations.MigrationsSqlGenerator.Generate(IReadOnlyList`1 operations, IModel model, MigrationsSqlGenerationOptions options)
at Microsoft.EntityFrameworkCore.Migrations.Internal.Migrator.GenerateUpSql(Migration migration, MigrationsSqlGenerationOptions options)
at MySql.EntityFrameworkCore.Migrations.Internal.MySQLMigrator.GenerateUpSql(Migration migration, MigrationsSqlGenerationOptions options)
at Microsoft.EntityFrameworkCore.Migrations.Internal.Migrator.<>c__DisplayClass16_2.b__2()
at Microsoft.EntityFrameworkCore.Migrations.Internal.Migrator.Migrate(String targetMigration)
at Microsoft.EntityFrameworkCore.Design.Internal.MigrationsOperations.UpdateDatabase(String targetMigration, String connectionString, String contextType)
at Microsoft.EntityFrameworkCore.Design.OperationExecutor.UpdateDatabaseImpl(String targetMigration, String connectionString, String contextType)
at Microsoft.EntityFrameworkCore.Design.OperationExecutor.UpdateDatabase.<>c__DisplayClass0_0.<.ctor>b__0()
at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.Execute(Action action)

对象引用未设置为对象的实例。

这个异常是MySQL EF Core提供程序与EF Core、.NET版本不兼容导致的，可按以下步骤解决：

• 统一EF Core版本：将所有EF Core相关NuGet包（包括Microsoft.EntityFrameworkCore、MySql.EntityFrameworkCore等）升级到8.x版本，确保与.NET 8 runtime完全匹配。
• 修正迁移文件：打开生成的UpdateFieldName迁移文件，检查RenameColumnOperation代码，确认OldName、NewName和table参数都正确赋值，无空值。示例正确代码：

  migrationBuilder.RenameColumn(
      name: "AddressId",
      table: "YourTableName",
      newName: "addressId");
  

• 重新生成迁移：先移除旧迁移，再重新生成并更新数据库：

  dotnet ef migrations remove
  dotnet ef migrations add UpdateFieldName
  dotnet ef database update
  

内容的提问来源于stack exchange，提问作者Ben