// строка подключения
public static string ConnectionString 
        {
            get 
            {
                EntityConnectionStringBuilder csb = new EntityConnectionStringBuilder();
                csb.ProviderConnectionString = "Data Source=msqlSer;Initial Catalog=testDB;User Id=TestUser;Password=1;Integrated Security=False;MultipleActiveResultSets=True;App=EntityFramework";
                csb.Provider = "System.Data.SqlClient";
                
                return csb.ToString();
            }
        }
// конструктор контекста
 public PeoplesContext()
            : base(ConnectionString)
        {
        }

public static string ConnectionString 
        {
            get 
            {
                SqlConnectionStringBuilder builder = new SqlConnectionStringBuilder();
                builder.DataSource = "msqlSer";
                builder.InitialCatalog = "testDB";
                builder.UserID = "TestUser";
                builder.Password = "1";
                builder.MultipleActiveResultSets = true;
                builder.PersistSecurityInfo = true;    
                return builder.ConnectionString.ToString();
        }