Sql-server – Could not connect to SQL Server localdb instance

localdbsql serversql-server-express

I have installed SQL Server 2014 localdb and SQL Server Management Studio. I am trying to connect to the localdb using a WPF application developed in Visual Studio.

Here is the connection string that I am using

<connectionStrings>
    <add name="ReservationContextString" 
         connectionString="Data Source=(localdb)\\MSSQLLocalDB;Initial Catalog=ReservationDB;AttachDbFilename=|DataDirectory|\\ReservationDB.mdf" 
         providerName="System.Data.SqlClient" />
</connectionStrings>

When I run the application I get the following exception

An exception of type 'System.Data.SqlClient.SqlException' occurred in EntityFramework.dll but was not handled in user code

Additional information: 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)

I am not sure why the application could not connect to localdb

Note: I am able to use the SQL Server Management Studio to connect to localdb using (localdb)\MSSQLLocalDB as Server Name. So, localdb seems to be installed properly.

Best Answer

Taking inspiration from this troubleshooting guide I was able to resolve the issue. The Entity Framework's defaultConnectionFactory should point to a localdb instance, but in app.config (or web.config), I had it set pointing to SQL Server Instance. It had to be changed to use localdb instance instead.

Old Entry

  <entityFramework>
      <defaultConnectionFactory type="System.Data.Entity.Infrastructure.SqlConnectionFactory, EntityFramework" />
      </defaultConnectionFactory>      
      ....
  </entityFramework>

should be (new code)

  <entityFramework>
    <defaultConnectionFactory type="System.Data.Entity.Infrastructure.LocalDbConnectionFactory, EntityFramework">
        <parameters>
          <parameter value="MSSQLLocalDB" />
        </parameters>
      </defaultConnectionFactory>      
      ..      
  </entityFramework>

Notice the System.Data.Entity.Infrastructure.LocalDbConnectionFactory, instead of System.Data.Entity.Infrastructure.SqlConnectionFactory

Syntax:

ALTER TABLE {TABLENAME} 
ADD {COLUMNNAME} {TYPE} {NULL|NOT NULL} 
CONSTRAINT {CONSTRAINT_NAME} DEFAULT {DEFAULT_VALUE}
WITH VALUES

Example:

ALTER TABLE SomeTable
        ADD SomeCol Bit NULL --Or NOT NULL.
 CONSTRAINT D_SomeTable_SomeCol --When Omitted a Default-Constraint Name is autogenerated.
    DEFAULT (0)--Optional Default-Constraint.
WITH VALUES --Add if Column is Nullable and you want the Default Value for Existing Records.

Notes:

Optional Constraint Name:
If you leave out CONSTRAINT D_SomeTable_SomeCol then SQL Server will autogenerate
a Default-Contraint with a funny Name like: DF__SomeTa__SomeC__4FB7FEF6

Optional With-Values Statement:
The WITH VALUES is only needed when your Column is Nullable
and you want the Default Value used for Existing Records.
If your Column is NOT NULL, then it will automatically use the Default Value
for all Existing Records, whether you specify WITH VALUES or not.

How Inserts work with a Default-Constraint:
If you insert a Record into SomeTable and do not Specify SomeCol's value, then it will Default to 0.
If you insert a Record and Specify SomeCol's value as NULL (and your column allows nulls),
then the Default-Constraint will not be used and NULL will be inserted as the Value.

Notes were based on everyone's great feedback below.
Special Thanks to:
@Yatrix, @WalterStabosz, @YahooSerious, and @StackMan for their Comments.

Sql – How to return only the Date from a SQL Server DateTime datatype

SELECT DATEADD(dd, 0, DATEDIFF(dd, 0, @your_date))

for example

SELECT DATEADD(dd, 0, DATEDIFF(dd, 0, GETDATE()))

gives me

2008-09-22 00:00:00.000

Pros:

No varchar<->datetime conversions required
No need to think about locale

Best Answer

Related Solutions

Sql – Add a column with a default value to an existing table in SQL Server

Syntax:

Example:

Notes:

Sql – How to return only the Date from a SQL Server DateTime datatype

Related Topic