Asp.Net Identity - A network-related or instance-specific error occurred while establishing a connection to SQL Server - sql-server

Question

I have a code first EF application. The database has been created. Now I am trying to implement Login/Registration module using the Asp.Net Identity. I click the Register link but it gives me the above error.
Web.config:
...
<connectionStrings>
<add name="ConnStr_Dev"
connectionString="Data Source = DELL-MyName; Initial Catalog = MyDB_Dev; user id = sa; password=myPassword;"
providerName="System.Data.SqlClient" />
<!--<add name="DefaultConnection"
connectionString="Data Source=(LocalDb)\MSSQLLocalDB;AttachDbFilename=|DataDirectory|\aspnet-MyApp-20170328111628.mdf;Initial Catalog=aspnet-MyApp-20170328111628;Integrated Security=True"
providerName="System.Data.SqlClient" />-->
</connectionStrings>
<appSettings>
<add key="webpages:Version" value="3.0.0.0" />
<add key="webpages:Enabled" value="false" />
<add key="ClientValidationEnabled" value="true" />
<add key="UnobtrusiveJavaScriptEnabled" value="true" />
</appSettings>
...
<entityFramework>
<defaultConnectionFactory
type="System.Data.Entity.Infrastructure.LocalDbConnectionFactory, EntityFramework">
<parameters>
<parameter value="Data Source = DELL-MyName; Initial Catalog = MyDB_Dev; user id = sa; password=myPassword;" />
</parameters>
</defaultConnectionFactory>
</entityFramework>
Is there something that needs to be set separately?

Answer 1

1- Use below connection string. I am using here SQL express instance. Replace it with the name you use to connect through sql management studio.
<connectionStrings>
<add name="ConnStr_Dev" connectionString="Server=.\SQLEXPRESS;Database=MyDB_Dev;User ID=sa;Password=myPassword;Trusted_Connection=False;Persist Security Info=False;Pooling=True;Min Pool Size=20;Max Pool Size=100;Connection Timeout=300;multipleactiveresultsets=True;App=EntityFramework" providerName="System.Data.SqlClient"/>
</connectionStrings>
2- Remove <entityFramework> tag from config file. You dont need it.
3- Make sure you are passing 'ConnStr_Dev' as string to DbContext constructor.

Answer 2

Locate the file IdentityModel.cs in the Models folder. In the ApplicationDbContext constructor the name of the connection string is passed in to the base class constructor - this needs to match the name of the your connection string in your web.config
So in your case
<connectionStrings>
<add name="ConnStr_Dev"
connectionString="Data Source = DELL-MyName; Initial Catalog = MyDB_Dev; user id = sa; password=myPassword;"
providerName="System.Data.SqlClient" />
</connectionStrings>
public class ApplicationDbContext : IdentityDbContext<ApplicationUser>
{
public ApplicationDbContext()
: base("ConnStr_Dev", throwIfV1Schema: false)
{
}
public static ApplicationDbContext Create()
{
return new ApplicationDbContext();
}
}