Using Entity framework with SQL Server 2012 (local *.mdf database)

I am trying to create a database in an MVC project. Code-First approach. I wrote my models and a DbContext database. I am having trouble making the connection to the database. My suspect that the problem is in my connection string but I am not sure. the database I want will consist of two tables, which are defined as follows:

public class EmployeeRequest
{
    [Key]
    public int EmployeeRequestId { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string UserName { get; set; }
    public int ExtNumber { get; set; }
    public bool isProcessed { get; set; }
    public virtual ICollection<ChangeOrder> ChangeOrders { get; set; }
}

and

public class ChangeOrder
{
    [Key]
    public int ChangeOrderId { get; set; }
    public short Operation { get; set; } //0 - Add, 1- delete
    public int TargetExt { get; set; }
    public short Status { get; set; } //0- Pending, 1- Approved, 2- Denied
    public DateTime DtRequested { get; set; }
    public DateTime DtProcessed { get; set; }
    public DateTime DtChangesApplied { get; set; }
    public int EmployeeRequestID { get; set; }
    public virtual EmployeeRequest Request { get; set; }
 }

The DbContext class is:

public class RequestsContext : DbContext
{
    public DbSet<EmployeeRequest> EmployeeRequests { get; set; }
    public DbSet<ChangeOrder> ChangeOrders { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
    }
}

Connection string:

<add name="RequestsContext" 
     providerName="System.Data.SqlClient" 
     connectionString="Data Source=(LocalDb);Database=Requests.mdf;Trusted_Connection=True"/>

The error I get says that the connection could not be made to the host.

I am nor sure why this is happening. Any Ideas?