如何首先在实体框架代码中使用MigratorScriptingDecorator？

Question

我在使用实体框架4.3.1中的MigratorScriptingDecorator.ScriptUpdate时遇到问题。

仅指定sourceMigration和targetMigration时，我的初始迁移被写入，其余迁移变为空。

我输入了包含复制代码的Microsoft Connect错误报告。 https://connect.microsoft.com/VisualStudio/feedback/details/731111/migratorscriptingdecorator-in-entity-framework-migrations-does-not-respect-sourcemigration-and-targetmigration

我希望MigratorScriptingDecorator.ScriptUpdate("from", "to")表现酷似相应的PM命令

PM> Update-Database -Script -SourceMigration from -TargetMigration to 

是否应ScriptUpdate相当于Update-Database -Script？
是否有任何其他方式从代码生成更新脚本？

Answer 1

正如链接的Microsoft Connect问题所述，问题是在若干MigratorScriptingDecorator s上重复使用相同的DbMigrator。

的原代码

DbMigrator efMigrator = new DbMigrator(new Configuration()); 
var pendingMigrations = efMigrator.GetLocalMigrations().ToList(); 
pendingMigrations.Insert(0, "0"); 
foreach (var migration in pendingMigrations.Zip(pendingMigrations.Skip(1), Tuple.Create)) 
{ 
    var sql = new MigratorScriptingDecorator(efMigrator).ScriptUpdate(migration.Item1, migration.Item2); // <-- problem here, the efMigrator is reused several times 
    Console.WriteLine("Migration from " + (migration.Item1 ?? "<null> ") + " to " + (migration.Item2 ?? "<null> ")); 
    Console.WriteLine(sql); 
    Console.WriteLine("-------------------------------------"); 
} 

的MigratorScriptingDecorator应该在循环外实例化这样的：

DbMigrator efMigrator = new DbMigrator(new Configuration()); 
var pendingMigrations = efMigrator.GetLocalMigrations().ToList(); 
pendingMigrations.Insert(0, "0"); 
var scriptMigrator = new MigratorScriptingDecorator(efMigrator); // <-- now only one MigratorScriptingDecorator is created for the DbMigrator 
foreach (var migration in pendingMigrations.Zip(pendingMigrations.Skip(1), Tuple.Create)) 
{ 
    var sql = scriptMigrator.ScriptUpdate(migration.Item1, migration.Item2); 
    Console.WriteLine("Migration from " + (migration.Item1 ?? "<null> ") + " to " + (migration.Item2 ?? "<null> ")); 
    Console.WriteLine(sql); 
    Console.WriteLine("-------------------------------------"); 
}