unable to create entity framework database in class library - entity-framework

Question

I have a class library. within this project I have a folder named 'models' with a few class models. I have all the references I need.
app.config:
<?xml version="1.0" encoding="utf-8"?>
<configuration>
<configSections>
<!-- For more information on Entity Framework configuration, visit http://go.microsoft.com/fwlink/?LinkID=237468 -->
<section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
</configSections>
<entityFramework>
<defaultConnectionFactory type="System.Data.Entity.Infrastructure.LocalDbConnectionFactory, EntityFramework">
<parameters>
<parameter value="mssqllocaldb" />
</parameters>
</defaultConnectionFactory>
<providers>
<provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer" />
</providers>
</entityFramework>
<connectionStrings>
<add name="DefaultConnection2" connectionString="Data Source=(LocalDb)\v11.0;Initial Catalog=MDD;AttachDbFilename=|DataDirectory|\MDD.mdf;Integrated Security=SSPI" providerName="System.Data.SqlClient" />
</connectionStrings>
<runtime>
<assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
<dependentAssembly>
<assemblyIdentity name="Microsoft.Owin" publicKeyToken="31bf3856ad364e35" culture="neutral" />
<bindingRedirect oldVersion="0.0.0.0-3.0.0.0" newVersion="3.0.0.0" />
</dependentAssembly>
</assemblyBinding>
</runtime>
</configuration>
After running update-database it throws the following error:
A file activation error occurred. The physical file name '\MDD.mdf'
may be incorrect. Diagnose and correct additional errors, and retry
the operation. CREATE DATABASE failed. Some file names listed could
not be created. Check related errors.

Answer 1

solved.
the app.config does not suppose to have <connectionStrings>. the Web.config do.
then in the MyDbContext.cs:
public MyDbContext():base("connectionString"){}