当 POCO 文件位于单独的项目中时将 EF 指向数据库
Pointing EF to a database when the POCO files are in a seperate project
我有一个 ASP.Net 解决方案，其中包含 3 个项目。包含我的数据库、API 项目和 UI 项目的代码优先 CS 文件的数据访问层 (DAL)。我已将 API 的 web.config 文件设置为指向我在 Azure 中的测试数据库，我已将 Entity Framework 安装到 API 和 DAL 中。
当我使用 UPDATE-DATABASE 从程序包管理器控制台转到 运行 我的第一次迁移时，我收到错误 No migrations configuration type was found in the assembly API 然后我 运行 Enable-Migrations 但得到错误 No context type was found in the assembly API。然后我将默认项目设置为 DAL 和 运行 Update-Database，它因网络连接错误而出错。我可以进入 MSSQL Studio 并使用我的连接字符串中的相同连接数据并登录就可以了。那我做错了什么？我怎样才能有一个单独的 DAL 项目，但仍然可以正常工作？
这是我得到的完整错误
PM> UPDATE-DATABASE Specify the '-Verbose' flag to view the SQL
statements being applied to the target database.
System.Data.SqlClient.SqlException (0x80131904): A network-related or
instance-specific error occurred while establishing a connection to
SQL Server. The server was not found or was not accessible. Verify
that the instance name is correct and that SQL Server is configured to
allow remote connections. (provider: SQL Network Interfaces, error: 26
- Error Locating Server/Instance Specified) at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException
exception, Boolean breakConnection, Action1 wrapCloseInAction) at
System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject
stateObj, Boolean callerHasConnectionLock, Boolean asyncClose) at
System.Data.SqlClient.TdsParser.Connect(ServerInfo serverInfo,
SqlInternalConnectionTds connHandler, Boolean ignoreSniOpenTimeout,
Int64 timerExpire, Boolean encrypt, Boolean trustServerCert, Boolean
integratedSecurity, Boolean withFailover) at
System.Data.SqlClient.SqlInternalConnectionTds.AttemptOneLogin(ServerInfo
serverInfo, String newPassword, SecureString newSecurePassword,
Boolean ignoreSniOpenTimeout, TimeoutTimer timeout, Boolean
withFailover) at
System.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover(ServerInfo
serverInfo, String newPassword, SecureString newSecurePassword,
Boolean redirectedUserInstance, SqlConnectionString connectionOptions,
SqlCredential credential, TimeoutTimer timeout) at
System.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist(TimeoutTimer
timeout, SqlConnectionString connectionOptions, SqlCredential
credential, String newPassword, SecureString newSecurePassword,
Boolean redirectedUserInstance) at
System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity
identity, SqlConnectionString connectionOptions, SqlCredential
credential, Object providerInfo, String newPassword, SecureString
newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString
userConnectionOptions, SessionData reconnectSessionData) at
System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions
options, DbConnectionPoolKey poolKey, Object poolGroupProviderInfo,
DbConnectionPool pool, DbConnection owningConnection,
DbConnectionOptions userOptions) at
System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnectionPool
pool, DbConnection owningObject, DbConnectionOptions options,
DbConnectionPoolKey poolKey, DbConnectionOptions userOptions) at
System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection
owningObject, DbConnectionOptions userOptions, DbConnectionInternal
oldConnection) at
System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection
owningObject, DbConnectionOptions userOptions, DbConnectionInternal
oldConnection) at
System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection
owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean
allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions
userOptions, DbConnectionInternal& connection) at
System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection
owningObject, TaskCompletionSource1 retry, DbConnectionOptions
userOptions, DbConnectionInternal& connection) at
System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection
owningConnection, TaskCompletionSource1 retry, DbConnectionOptions
userOptions, DbConnectionInternal oldConnection, DbConnectionInternal&
connection) at
System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection
outerConnection, DbConnectionFactory connectionFactory,
TaskCompletionSource1 retry, DbConnectionOptions userOptions) at
System.Data.ProviderBase.DbConnectionClosed.TryOpenConnection(DbConnection
outerConnection, DbConnectionFactory connectionFactory,
TaskCompletionSource1 retry, DbConnectionOptions userOptions) at
System.Data.SqlClient.SqlConnection.TryOpenInner(TaskCompletionSource1
retry) at
System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource1
retry) at System.Data.SqlClient.SqlConnection.Open() at
System.Data.Entity.Infrastructure.Interception.DbConnectionDispatcher.<Open>b__36(DbConnection
t, DbConnectionInterceptionContext c) at
System.Data.Entity.Infrastructure.Interception.InternalDispatcher1.Dispatch[TTarget,TInterceptionContext](TTarget
target, Action2 operation, TInterceptionContext interceptionContext,
Action3 executing, Action3 executed) at
System.Data.Entity.Infrastructure.Interception.DbConnectionDispatcher.Open(DbConnection
connection, DbInterceptionContext interceptionContext) at
System.Data.Entity.SqlServer.SqlProviderServices.<>c__DisplayClass33.<UsingConnection>b__32()
at
System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.<>c__DisplayClass1.<Execute>b__0()
at
System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute[TResult](Func1
operation) at
System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute(Action
operation) at
System.Data.Entity.SqlServer.SqlProviderServices.UsingConnection(DbConnection
sqlConnection, Action1 act) at
System.Data.Entity.SqlServer.SqlProviderServices.UsingMasterConnection(DbConnection
sqlConnection, Action1 act) at
System.Data.Entity.SqlServer.SqlProviderServices.CreateDatabaseFromScript(Nullable1
commandTimeout, DbConnection sqlConnection, String
createDatabaseScript) at
System.Data.Entity.SqlServer.SqlProviderServices.DbCreateDatabase(DbConnection
connection, Nullable1 commandTimeout, StoreItemCollection
storeItemCollection) at
System.Data.Entity.Core.Common.DbProviderServices.CreateDatabase(DbConnection
connection, Nullable`1 commandTimeout, StoreItemCollection
storeItemCollection) at
System.Data.Entity.Core.Objects.ObjectContext.CreateDatabase() at
System.Data.Entity.Migrations.Utilities.DatabaseCreator.Create(DbConnection
connection) at
System.Data.Entity.Migrations.DbMigrator.EnsureDatabaseExists(Action
mustSucceedToKeepDatabase) at
System.Data.Entity.Migrations.Infrastructure.MigratorBase.EnsureDatabaseExists(Action
mustSucceedToKeepDatabase) at
System.Data.Entity.Migrations.DbMigrator.Update(String
targetMigration) at
System.Data.Entity.Migrations.Infrastructure.MigratorBase.Update(String
targetMigration) at
System.Data.Entity.Migrations.Design.ToolingFacade.UpdateRunner.Run()
at System.AppDomain.DoCallBack(CrossAppDomainDelegate
callBackDelegate) at
System.AppDomain.DoCallBack(CrossAppDomainDelegate callBackDelegate)
at System.Data.Entity.Migrations.Design.ToolingFacade.Run(BaseRunner
runner) at
System.Data.Entity.Migrations.Design.ToolingFacade.Update(String
targetMigration, Boolean force) at
System.Data.Entity.Migrations.UpdateDatabaseCommand.<>c__DisplayClass2.<.ctor>b__0()
at
System.Data.Entity.Migrations.MigrationsDomainCommand.Execute(Action
command) ClientConnectionId:00000000-0000-0000-0000-000000000000 Error
Number:-1,State:0,Class:20 A network-related or instance-specific
error occurred while establishing a connection to SQL Server. The
server was not found or was not accessible. Verify that the instance
name is correct and that SQL Server is configured to allow remote
connections. (provider: SQL Network Interfaces, error: 26 - Error
Locating Server/Instance Specified)
看来你一直在改变一些东西。这应该可以解决您的问题：
- 在您需要的项目中安装 Entity-Framework（DAL 和 API）。
- 在 DAL 中创建
DbContext 继承 class。
- 在 DAL 中安装迁移 (
enable-migrations)。
- 将您的连接字符串放入 DAL 的 App.Config 和 API 的 Web.Config .
- 将 DAL 设置为默认项目。
- 使用
update-database 执行迁移，如果 AutomaticMigrationsEnabled 为 false，可选择调用 add-migration "mymigration"。
您还可以在 API 项目中安装 Migrations，并使用 enable-migrations -contextassemblyname "DAL" 将 DbContext 保留在 DAL 项目中。这将允许您只使用 API 的配置文件，而不必将其也复制到 DAL 项目中。随后您可以从 API 项目调用 update-database，因为现在 Migrations 已安装在此处。
这就是你出错的地方：你在 DAL 中安装了 Migrations（这意味着你必须将 DAL 设置为你的启动项目）但你只将连接字符串放在 API 中。 只有设置为启动的项目才会加载其配置文件！
当您发布您的应用程序时，它将使用您在 API 中提供的连接字符串，所以这一切都很好：此时您不必执行任何迁移。
另一种选择是通过添加
强制 EF 包管理器使用正确的连接字符串和提供程序
Update-Database -ConnectionString "Data Source=(LocalDb)\v11...." -ConnectionProviderName "System.Data.SqlClient"
我有一个 ASP.Net 解决方案，其中包含 3 个项目。包含我的数据库、API 项目和 UI 项目的代码优先 CS 文件的数据访问层 (DAL)。我已将 API 的 web.config 文件设置为指向我在 Azure 中的测试数据库，我已将 Entity Framework 安装到 API 和 DAL 中。
当我使用 UPDATE-DATABASE 从程序包管理器控制台转到 运行 我的第一次迁移时，我收到错误 No migrations configuration type was found in the assembly API 然后我 运行 Enable-Migrations 但得到错误 No context type was found in the assembly API。然后我将默认项目设置为 DAL 和 运行 Update-Database，它因网络连接错误而出错。我可以进入 MSSQL Studio 并使用我的连接字符串中的相同连接数据并登录就可以了。那我做错了什么？我怎样才能有一个单独的 DAL 项目，但仍然可以正常工作？
这是我得到的完整错误
PM> UPDATE-DATABASE Specify the '-Verbose' flag to view the SQL statements being applied to the target database. System.Data.SqlClient.SqlException (0x80131904): A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified) at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection, Action
1 wrapCloseInAction) at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose) at System.Data.SqlClient.TdsParser.Connect(ServerInfo serverInfo, SqlInternalConnectionTds connHandler, Boolean ignoreSniOpenTimeout, Int64 timerExpire, Boolean encrypt, Boolean trustServerCert, Boolean integratedSecurity, Boolean withFailover) at System.Data.SqlClient.SqlInternalConnectionTds.AttemptOneLogin(ServerInfo serverInfo, String newPassword, SecureString newSecurePassword, Boolean ignoreSniOpenTimeout, TimeoutTimer timeout, Boolean withFailover) at System.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover(ServerInfo serverInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString connectionOptions, SqlCredential credential, TimeoutTimer timeout) at System.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist(TimeoutTimer timeout, SqlConnectionString connectionOptions, SqlCredential credential, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance) at System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, SqlCredential credential, Object providerInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString userConnectionOptions, SessionData reconnectSessionData) at System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, DbConnectionPoolKey poolKey, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection, DbConnectionOptions userOptions) at System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnectionPool pool, DbConnection owningObject, DbConnectionOptions options, DbConnectionPoolKey poolKey, DbConnectionOptions userOptions) at System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection) at System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection) at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection) at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSource1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection) at System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource1 retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, DbConnectionInternal& connection) at System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource1 retry, DbConnectionOptions userOptions) at System.Data.ProviderBase.DbConnectionClosed.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource1 retry, DbConnectionOptions userOptions) at System.Data.SqlClient.SqlConnection.TryOpenInner(TaskCompletionSource1 retry) at System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource1 retry) at System.Data.SqlClient.SqlConnection.Open() at System.Data.Entity.Infrastructure.Interception.DbConnectionDispatcher.<Open>b__36(DbConnection t, DbConnectionInterceptionContext c) at System.Data.Entity.Infrastructure.Interception.InternalDispatcher1.Dispatch[TTarget,TInterceptionContext](TTarget target, Action2 operation, TInterceptionContext interceptionContext, Action3 executing, Action3 executed) at System.Data.Entity.Infrastructure.Interception.DbConnectionDispatcher.Open(DbConnection connection, DbInterceptionContext interceptionContext) at System.Data.Entity.SqlServer.SqlProviderServices.<>c__DisplayClass33.<UsingConnection>b__32() at System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.<>c__DisplayClass1.<Execute>b__0() at System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute[TResult](Func1 operation) at System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute(Action operation) at System.Data.Entity.SqlServer.SqlProviderServices.UsingConnection(DbConnection sqlConnection, Action1 act) at System.Data.Entity.SqlServer.SqlProviderServices.UsingMasterConnection(DbConnection sqlConnection, Action1 act) at System.Data.Entity.SqlServer.SqlProviderServices.CreateDatabaseFromScript(Nullable1 commandTimeout, DbConnection sqlConnection, String createDatabaseScript) at System.Data.Entity.SqlServer.SqlProviderServices.DbCreateDatabase(DbConnection connection, Nullable1 commandTimeout, StoreItemCollection storeItemCollection) at System.Data.Entity.Core.Common.DbProviderServices.CreateDatabase(DbConnection connection, Nullable`1 commandTimeout, StoreItemCollection storeItemCollection) at System.Data.Entity.Core.Objects.ObjectContext.CreateDatabase() at System.Data.Entity.Migrations.Utilities.DatabaseCreator.Create(DbConnection connection) at System.Data.Entity.Migrations.DbMigrator.EnsureDatabaseExists(Action mustSucceedToKeepDatabase) at System.Data.Entity.Migrations.Infrastructure.MigratorBase.EnsureDatabaseExists(Action mustSucceedToKeepDatabase) at System.Data.Entity.Migrations.DbMigrator.Update(String targetMigration) at System.Data.Entity.Migrations.Infrastructure.MigratorBase.Update(String targetMigration) at System.Data.Entity.Migrations.Design.ToolingFacade.UpdateRunner.Run() at System.AppDomain.DoCallBack(CrossAppDomainDelegate callBackDelegate) at System.AppDomain.DoCallBack(CrossAppDomainDelegate callBackDelegate)
at System.Data.Entity.Migrations.Design.ToolingFacade.Run(BaseRunner runner) at System.Data.Entity.Migrations.Design.ToolingFacade.Update(String targetMigration, Boolean force) at System.Data.Entity.Migrations.UpdateDatabaseCommand.<>c__DisplayClass2.<.ctor>b__0() at System.Data.Entity.Migrations.MigrationsDomainCommand.Execute(Action command) ClientConnectionId:00000000-0000-0000-0000-000000000000 Error Number:-1,State:0,Class:20 A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified)
看来你一直在改变一些东西。这应该可以解决您的问题：
- 在您需要的项目中安装 Entity-Framework（DAL 和 API）。
- 在 DAL 中创建
DbContext继承 class。 - 在 DAL 中安装迁移 (
enable-migrations)。 - 将您的连接字符串放入 DAL 的 App.Config 和 API 的 Web.Config .
- 将 DAL 设置为默认项目。
- 使用
update-database执行迁移，如果AutomaticMigrationsEnabled为false，可选择调用add-migration "mymigration"。
您还可以在 API 项目中安装 Migrations，并使用 enable-migrations -contextassemblyname "DAL" 将 DbContext 保留在 DAL 项目中。这将允许您只使用 API 的配置文件，而不必将其也复制到 DAL 项目中。随后您可以从 API 项目调用 update-database，因为现在 Migrations 已安装在此处。
这就是你出错的地方：你在 DAL 中安装了 Migrations（这意味着你必须将 DAL 设置为你的启动项目）但你只将连接字符串放在 API 中。 只有设置为启动的项目才会加载其配置文件！
当您发布您的应用程序时，它将使用您在 API 中提供的连接字符串，所以这一切都很好：此时您不必执行任何迁移。
另一种选择是通过添加
强制 EF 包管理器使用正确的连接字符串和提供程序Update-Database -ConnectionString "Data Source=(LocalDb)\v11...." -ConnectionProviderName "System.Data.SqlClient"