代码优先实体框架无法连接到数据库

Question

i know this question must be answered before but i can't find a solution to my case. i created a service-based database in visual studio 2013, and i want to connect to this database. i created the dbSet, the class heritating from DbContext and added the entitiframework reference everything is fine, except the connectionstring

<connectionStrings>
<add name ="master" connectionString="Data Source=(localdb)\v11.0;
                      AttachDbFilename=c:\users\reda\documents\visual studio 2013\Projects\Testing new things\Testing new things\master.mdf;
                      Integrated Security=True;"/>  </connectionStrings>

when i run my program i get a Data.Entity.Core.ProviderIncompatibleException exception; which means that it can't access the database, where am i wrong?

btw, is there any other solution to work with a local database?

the error message is:

    Unhandled Exception: System.Data.Entity.Core.ProviderIncompatibleException: An e
rror occurred accessing the database. This usually means that the connection to
the database failed. Check that the connection string is correct and that the ap
propriate DbContext constructor is being used to specify it or find it in the ap
plication's config file. See http://go.microsoft.com/fwlink/?LinkId=386386 for i
nformation on DbContext and connections. See the inner exception for details of
the failure. ---> System.Data.Entity.Core.ProviderIncompatibleException: The pro
vider did not return a ProviderManifestToken string. ---> System.Data.SqlClient.
SqlException: A network-related or instance-specific error occurred while establ
ishing a connection to SQL Server. The server was not found or was not accessibl
e. Verify that the instance name is correct and that SQL Server is configured to
 allow remote connections. (provider: SQL Network Interfaces, error: 50 - Local
Database Runtime error occurred. The specified LocalDB instance does not exist.
)
   at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception
, Boolean breakConnection, Action`1 wrapCloseInAction)
   at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObj
ect stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
   at System.Data.SqlClient.TdsParser.Connect(ServerInfo serverInfo, SqlInternal
ConnectionTds connHandler, Boolean ignoreSniOpenTimeout, Int64 timerExpire, Bool
ean encrypt, Boolean trustServerCert, Boolean integratedSecurity, Boolean withFa
ilover)
   at System.Data.SqlClient.SqlInternalConnectionTds.AttemptOneLogin(ServerInfo
serverInfo, String newPassword, SecureString newSecurePassword, Boolean ignoreSn
iOpenTimeout, TimeoutTimer timeout, Boolean withFailover)
   at System.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover(ServerInfo
serverInfo, String newPassword, SecureString newSecurePassword, Boolean redirect
edUserInstance, SqlConnectionString connectionOptions, SqlCredential credential,
 TimeoutTimer timeout)
   at System.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist(TimeoutTime
r timeout, SqlConnectionString connectionOptions, SqlCredential credential, Stri
ng newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance)
   at System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdent
ity identity, SqlConnectionString connectionOptions, SqlCredential credential, O
bject providerInfo, String newPassword, SecureString newSecurePassword, Boolean
redirectedUserInstance, SqlConnectionString userConnectionOptions, SessionData r
econnectSessionData)
   at System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOp
tions options, DbConnectionPoolKey poolKey, Object poolGroupProviderInfo, DbConn
ectionPool pool, DbConnection owningConnection, DbConnectionOptions userOptions)

   at System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConn
ectionPool pool, DbConnection owningObject, DbConnectionOptions options, DbConne
ctionPoolKey poolKey, DbConnectionOptions userOptions)
   at System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owning
Object, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)
   at System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection o
wningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection
)
   at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection ow
ningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean o
nlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& co
nnection)
   at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection ow
ningObject, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbCon
nectionInternal& connection)
   at System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection
 owningConnection, TaskCompletionSource`1 retry, DbConnectionOptions userOptions
, DbConnectionInternal oldConnection, DbConnectionInternal& connection)
   at System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(Db
Connection outerConnection, DbConnectionFactory connectionFactory, TaskCompletio
nSource`1 retry, DbConnectionOptions userOptions)
   at System.Data.ProviderBase.DbConnectionClosed.TryOpenConnection(DbConnection
 outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1
retry, DbConnectionOptions userOptions)
   at System.Data.SqlClient.SqlConnection.TryOpenInner(TaskCompletionSource`1 re
try)
   at System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry)
   at System.Data.SqlClient.SqlConnection.Open()
   at System.Data.Entity.Infrastructure.Interception.DbConnectionDispatcher.<Ope
n>b__38(DbConnection t, DbConnectionInterceptionContext c)
   at System.Data.Entity.Infrastructure.Interception.InternalDispatcher`1.Dispat
ch[TTarget,TInterceptionContext](TTarget target, Action`2 operation, TIntercepti
onContext interceptionContext, Action`3 executing, Action`3 executed)
   at System.Data.Entity.Infrastructure.Interception.DbConnectionDispatcher.Open
(DbConnection connection, DbInterceptionContext interceptionContext)
   at System.Data.Entity.SqlServer.SqlProviderServices.<>c__DisplayClass31.<Usin
gConnection>b__2f()
   at System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.<>c__DisplayClass
1.<Execute>b__0()
   at System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute[TResult](
Func`1 operation)
   at System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute(Action op
eration)
   at System.Data.Entity.SqlServer.SqlProviderServices.UsingConnection(DbConnect
ion sqlConnection, Action`1 act)
   at System.Data.Entity.SqlServer.SqlProviderServices.UsingMasterConnection(DbC
onnection sqlConnection, Action`1 act)
   at System.Data.Entity.SqlServer.SqlProviderServices.GetDbProviderManifestToke
n(DbConnection connection)
   at System.Data.Entity.Core.Common.DbProviderServices.GetProviderManifestToken
(DbConnection connection)
   --- End of inner exception stack trace ---
   at System.Data.Entity.Core.Common.DbProviderServices.GetProviderManifestToken
(DbConnection connection)
   at System.Data.Entity.Utilities.DbProviderServicesExtensions.GetProviderManif
estTokenChecked(DbProviderServices providerServices, DbConnection connection)
   --- End of inner exception stack trace ---
   at System.Data.Entity.Utilities.DbProviderServicesExtensions.GetProviderManif
estTokenChecked(DbProviderServices providerServices, DbConnection connection)
   at System.Data.Entity.Infrastructure.DefaultManifestTokenResolver.<>c__Displa
yClass1.<ResolveManifestToken>b__0(Tuple`3 k)
   at System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd(TKey key, Fu
nc`2 valueFactory)
   at System.Data.Entity.Infrastructure.DefaultManifestTokenResolver.ResolveMani
festToken(DbConnection connection)
   at System.Data.Entity.Utilities.DbConnectionExtensions.GetProviderInfo(DbConn
ection connection, DbProviderManifest& providerManifest)
   at System.Data.Entity.DbModelBuilder.Build(DbConnection providerConnection)
   at System.Data.Entity.Internal.LazyInternalContext.CreateModel(LazyInternalCo
ntext internalContext)
   at System.Data.Entity.Internal.RetryLazy`2.GetValue(TInput input)
   at System.Data.Entity.Internal.LazyInternalContext.InitializeContext()
   at System.Data.Entity.Internal.InternalContext.GetEntitySetAndBaseTypeForType
(Type entityType)
   at System.Data.Entity.Internal.Linq.InternalSet`1.Initialize()
   at System.Data.Entity.Internal.Linq.InternalSet`1.get_InternalContext()
   at System.Data.Entity.Internal.Linq.InternalSet`1.ActOnSet(Action action, Ent
ityState newState, Object entity, String methodName)
   at System.Data.Entity.Internal.Linq.InternalSet`1.Add(Object entity)
   at System.Data.Entity.DbSet`1.Add(TEntity entity)
   at Testing_new_things.Program.Main(String[] args) in c:\Users\Reda\Documents\
Visual Studio 2013\Projects\Testing new things\Testing new things\Program.cs:lin
e 19
Press any key to continue . . .

Answer 1

Your connection string is missing the provider information. Change it to this

<add name ="master" connectionString="Data Source=(localdb)\v11.0;
                  AttachDbFilename=c:\users\reda\documents\visual studio 2013\Projects\Testing new things\Testing new things\master.mdf;
                  Integrated Security=True;"
providerName="System.Data.SqlClient"/>