EntityFramework代码优先自定义连接字符串和迁移

Question

当我使用默认连接字符串(从中读取app.config)创建上下文时,将创建数据库并且迁移工作 - 基本上所有内容都是有序的.而以编程方式(使用SqlConnectionStringBuilder)创建连接字符串时:

• 数据库不存在时不创建数据库(场景A);
• CreateDbIfNotExists()创建最新版本的数据库模型,但不调用迁移机制(方案B).

在A我希望访问数据库时抛出异常,因为 - 显然 - 它不在那里.在B数据库中创建正确的迁移机制不会被调用,就像标准连接字符串中的情况一样.

app.config:" Data Source=localhost\\SQLEXPRESS;Initial Catalog=Db13;User ID=xxx;Password=xxx"

建设者:

sqlBuilder.DataSource = x.DbHost;
sqlBuilder.InitialCatalog = x.DbName;
sqlBuilder.UserID = x.DbUser;
sqlBuilder.Password = x.DbPassword;

初始化程序:

Database.SetInitializer(
    new MigrateDatabaseToLatestVersion<
        MyContext,
        Migrations.Configuration
    >()
);

规范:实体框架:5.0,DB:SQL Server Express 2008

Answer 1

如果您的迁移无法正常工作,请尝试Database.Initialize(true)在DbContext ctor中设置.

public CustomContext(DbConnection connection)
: base(connection, true)    
{    
        Database.Initialize(true);    
}    

我有类似的迁移问题.在我的解决方案中,我必须始终在ctor中设置数据库初始化程序,如下所示

public CustomContext(DbConnection connection)
: base(connection, true)    
{    
        Database.SetInitializer(new CustomInitializer());
        Database.Initialize(true);    
}    

在自定义初始化程序中,您必须实现InitalizeDatabase(CustomContex context)方法,例如.

class CustomInitializer : IDatabaseInitializer<CustomContext>
{
    public void InitializeDatabase(CustomContext context)
    {
        if (!context.Database.Exists || !context.Database.CompatibleWithModel(false))
        {
            var configuration = new Configuration();
            var migrator = new DbMigrator(configuration);
            migrator.Configuration.TargetDatabase = new DbConnectionInfo(context.Database.Connection.ConnectionString, "System.Data.SqlClient");
            var migrations = migrator.GetPendingMigrations();
            if (migrations.Any())
            {
                var scriptor = new MigratorScriptingDecorator(migrator);
                string script = scriptor.ScriptUpdate(null, migrations.Last());
                if (!String.IsNullOrEmpty(script))
                {
                    context.Database.ExecuteSqlCommand(script);
                }
            }
        }
    }
}

更新

Answer 2

他是一个解决方案,在app.config中没有连接字符串.使用相同的上下文使用自动迁移和2个数据库.真正的运行时提供了Connection.方法.

APP.CONFIG(使用EF 6)

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <configSections>
<section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework,     Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
 </configSections>
 <startup>
<supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
</startup>
 <entityFramework>
<defaultConnectionFactory type="System.Data.Entity.Infrastructure.SqlConnectionFactory, EntityFramework">
  <parameters>
    <parameter value="Data Source=localhost; Integrated Security=True; MultipleActiveResultSets=True" />
  </parameters>
</defaultConnectionFactory>
 </entityFramework>
</configuration>

我重写了代码,使Demo尽可能小:

using System;
using System.Data.Common;
using System.Data.Entity;
using System.Data.Entity.Infrastructure;
using System.Data.Entity.Migrations;

namespace Ef6Test {
    public class Program {
    public static void Main(string[] args) {
        Database.SetInitializer(new MigrateDatabaseToLatestVersion<Ef6Ctx, Ef6MigConf>());
        WhichDb.DbName = "HACKDB1";
        var sqlConn = GetSqlConn4DBName(WhichDb.DbName);
        var context = new Ef6Ctx(sqlConn);
        context.Database.Initialize(true);
        AddJunk(context);
        //sqlConn.Close();  //?? whatever other considerations, dispose of context etc...

        Database.SetInitializer(new MigrateDatabaseToLatestVersion<Ef6Ctx, Ef6MigConf>()); // yes its default again reset this !!!!
        WhichDb.DbName = "HACKDB2";
        var sqlConn2 = GetSqlConn4DBName(WhichDb.DbName);
        var context2 = new Ef6Ctx(sqlConn2);
        context2.Database.Initialize(true);
        AddJunk(context2);
    }
    public static class WhichDb { // used during migration to know which connection to build
        public static string DbName { get; set; }
    }
    private static void AddJunk(DbContext context) {
        var poco = new pocotest();
        poco.f1 = DateTime.Now.ToString();
      //  poco.f2 = "Did somebody step on a duck?";  //comment in for second run
        context.Set<pocotest>().Add(poco);
        context.SaveChanges();
    }
    public static DbConnection GetSqlConn4DBName(string dbName) {
        var sqlConnFact =
            new SqlConnectionFactory(
                "Data Source=localhost; Integrated Security=True; MultipleActiveResultSets=True");
        var sqlConn = sqlConnFact.CreateConnection(dbName);
        return sqlConn;
    }
}
public class MigrationsContextFactory : IDbContextFactory<Ef6Ctx> {
    public Ef6Ctx Create() {
        var sqlConn = Program.GetSqlConn4DBName(Program.WhichDb.DbName); // NASTY but it works
        return new Ef6Ctx(sqlConn);
    }
}
public class Ef6MigConf : DbMigrationsConfiguration<Ef6Ctx> {
    public Ef6MigConf() {
        AutomaticMigrationsEnabled = true;
        AutomaticMigrationDataLossAllowed = true;
    }
}
public class pocotest {
    public int Id { get; set; }
    public string f1 { get; set; }
 //   public string f2 { get; set; } // comment in for second run
}
public class Ef6Ctx : DbContext {
    public DbSet<pocotest> poco1s { get; set; }
    public Ef6Ctx(DbConnection dbConn) : base(dbConn, true) { }
}
}