EntityFramework在哪里获得到本地数据库的连接字符串？

Question

I have created a web form that is a registration form using Identity. The form calls code behind that looks like this:

protected void CreateUser_Click(object sender, EventArgs e)
{
    var userStore = new UserStore<IdentityUser>();
    var manager = new UserManager<IdentityUser>(userStore);

    var user = new IdentityUser() { UserName = UserName.Text };
    IdentityResult result = manager.Create(user, Password.Text);

    if (result.Succeeded)
    {
        StatusMessage.Text = string.Format("User {0} was created successfully!", user.UserName);
    }
    else
    {
        StatusMessage.Text = result.Errors.FirstOrDefault();
    }
}

And my web config file is this:

<?xml version="1.0" encoding="utf-8"?>
<configuration>
    <configSections>
        <section
         name="entityFramework"
         type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"
         requirePermission="false" />
    </configSections>
    <system.web>
        <authentication mode="Forms" /> 
        <roleManager enabled="true" />
        <compilation debug="true" targetFramework="4.5" /> 
        <httpRuntime targetFramework="4.5" />
    </system.web>
    <runtime>
        <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
            <dependentAssembly>
                <assemblyIdentity name="Microsoft.Owin" publicKeyToken="31bf3856ad364e35" culture="neutral" />
                <bindingRedirect oldVersion="0.0.0.0-3.0.1.0" newVersion="3.0.1.0" />
            </dependentAssembly>
        </assemblyBinding>
    </runtime>
</configuration>

I also have MS SQL Express installed on my machine. When i use the form the app creates a database in SQLExpress called DefaultConnection.

My question is how does entity/identity/.net know about my database at all, since I don't have the connection string written anywhere explicitly?

If this is somehow a feature of 'convention over configuration' then how can I explicitly direct entity to a different database?

Edit:

I have tried adding

<add name="MyConnection"
  connectionString="[the connection string];TrustServerCertificate=False"
  providerName="System.Data.SqlClient" />`

to the connection strings and updated my create user code:

...
var connString = ConfigurationManager.ConnectionStrings["MyConnection"].ConnectionString;
var context = new System.Data.Entity.DbContext(connString);

var userStore = new UserStore<IdentityUser>(context);
var manager = new UserManager<IdentityUser>(userStore);
...

but this threw a InvalidOperationException with the following message:

Additional information: The entity type IdentityUser is not part of the model for the current context.

Last Edit:

Found out how to avoid the exception, changed this:

var context = new System.Data.Entity.DbContext(connString);

into this:

var context = new Microsoft.AspNet.Identity.EntityFramework.IdentityDbContext(connString);

Answer 1

By convention a local database will be created on your local SQL Server instance.

See: Code First to a New Database - MSDN

By convention DbContext has created a database for you.

• If a local SQL Express instance is available (installed by default with Visual Studio 2010) then Code First has created the database on that instance
• If SQL Express isn't available then Code First will try and use LocalDb (installed by default with Visual Studio 2012)
• The database is named after the fully qualified name of the derived context

You can over come it by specifying an explicit connection string in web.config like:

<configuration>
  <connectionStrings>
    <add name="MyDBContext"
         connectionString="Data Source=SQLServerAddress;Integrated Security=SSPI;Initial Catalog=yourdbName"
         providerName="System.Data.SqlClient" />
  </connectionStrings>
</configuration>

Here remember to change the name to the class that is extending DbContext in your code.

So for example if you are extending DbContext as:

public class MyDBContext : DbContext

then use MyDBContext as key for connection string in the configuration.

or off course you can pass the connection string in the constructor:

namespace MyCodeFirstProject 
{     
    public class MyDBContext: DbContext     
    {         
        public MyDBContext() : 
            base("Data Source=SQLServerAddress;Integrated Security=SSPI;Initial Catalog=yourdbName") {}
    }
}