错误信息:

“自数据库创建以来,支持‘AddressBook’上下文的模型已经发生了变化。手动删除/更新数据库,或者调用database。带有IDatabaseInitializer实例的SetInitializer。例如,RecreateDatabaseIfModelChanges策略将自动删除并重新创建数据库,并可选地为其添加新数据。”

我正在尝试使用代码优先功能,以下是我写的:

var modelBuilder = new ModelBuilder();
var model = modelBuilder.CreateModel();
using (AddressBook context = new AddressBook(model))
{
    var contact = new Contact
    {
        ContactID = 10000,
        FirstName = "Brian",
        LastName = "Lara",
        ModifiedDate = DateTime.Now,
        AddDate = DateTime.Now,
        Title = "Mr."

    };
    context.contacts.Add(contact);
    int result = context.SaveChanges();
    Console.WriteLine("Result :- "+ result.ToString());
}

上下文类:

public class AddressBook : DbContext
{
    public AddressBook()
    { }
    public AddressBook(DbModel AddressBook)
        : base(AddressBook)
    {

    }
    public DbSet<Contact> contacts { get; set; }
    public DbSet<Address> Addresses { get; set; }
}

和连接字符串:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <connectionStrings>
    <add name="AddressBook" providerName="System.Data.SqlClient"  
         connectionString="Data Source=MyMachine;Initial Catalog=AddressBook;
         Integrated Security=True;MultipleActiveResultSets=True;"/>
    </connectionStrings>
</configuration>

因此,数据库名称是“AddressBook”,当我试图将联系人对象添加到上下文时发生错误。我遗漏了什么吗?


当前回答

现在是:

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    Database.SetInitializer<YourDbContext>(null);
    base.OnModelCreating(modelBuilder);
}

在你的YourDbContext.cs文件中。

其他回答

在sql Server Management Studio中执行如下sql命令:

delete FROM [dbo].[__MigrationHistory]

I had the same issue - re-adding the migration and updating the database didn't work and none of the answers above seemed right. Then inspiration hit me - I'm using multiple tiers (one web, one data, and one business). The data layer has the context and all the models. The web layer never threw this exception - it was the business layer (which I set as console application for testing and debugging). Turns out the business layer wasn't using the right connection string to get the db and make the context. So I added the connection string to the app config of the business layer (and the data layer) and viola it works. Putting this here for others who may encounter the same issue.

我有这个问题,原来是一个项目指向SQLExpress,但有问题的是指向LocalDb。(在它们各自的web.config中)。愚蠢的疏忽,但值得注意的是,如果其他人正在排除这个问题。

或者你可以把这一行放在你的Global.asax.cs文件中的Application_Start():

System.Data.Entity.Database.SetInitializer(new System.Data.Entity.DropCreateDatabaseIfModelChanges<ProjectName.Path.Context>());

确保将ProjectName.Path.Context更改为您的名称空间和上下文。如果先使用代码,那么每当对模式进行任何更改时,都会删除并创建一个新数据库。

当我们为两个应用程序使用一个数据库时,我遇到了同样的问题。设置disableDatabaseInitialization="true"在上下文类型节为我工作。

<entityFramework>
<providers>
  <provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer" />
</providers>
<contexts>
  <context type="PreferencesContext, Preferences" disableDatabaseInitialization="true">
    <databaseInitializer type="System.Data.Entity.MigrateDatabaseToLatestVersion`2[[PreferencesContext, Preferences], [Migrations.Configuration, Preferences]], EntityFramework" />
  </context>
</contexts>

详情https://msdn.microsoft.com/en-us/data/jj556606.aspx