public partial class MyDatabaseEntities : DbContext
{
public MyDatabaseEntities(string connectionString)
    : base(connectionString)
{
}

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    throw new UnintentionalCodeFirstException();
}

public virtual DbSet<MyTable> MyTable { get; set; }

string myConnectionString = "...";
MyDatabaseEntities = new MyDatabaseEntities(myConnectionString);

سلام آقاي مدائني عزيز 

اون دو خط آخر رو بايد تو كدوم كلاس استفاده كنم ؟ 

سلام دوست من

unit Of Work

اين پيام بلند بالا رو زحمت كشيد داد : 

An exception of type 'System.Data.Entity.Infrastructure.UnintentionalCodeFirstException' occurred in DAL.dll but was not handled in user code

Additional information: The context is being used in Code First mode with code that was generated from an EDMX file for either Database First or Model First development.  This will not work correctly. To fix this problem do not remove the line of code that throws this exception. If you wish to use Database First or Model First, then make sure that the Entity Framework connection string is included in the app.config or web.config of the start-up project. If you are creating your own DbConnection, then make sure that it is an EntityConnection and not some other type of DbConnection, and that you pass it to one of the base DbContext constructors that take a DbConnection. To learn more about Code First, Database First, and Model First see the Entity Framework documentation here: http://go.microsoft.com/fwlink/?LinkId=394715

کدی که نوشتید را قرار دهید

سلام مجدد خدمت مهندس عزيز 

من از روش Database First استفاده كردم . كدهاي داخل UnitOfWork من : 

namespace DAL
{
    public class UnitOfWork : IDisposable
    {
        private static string conn = "Data Source=.;Initial Catalog=SaatSchool;Persist Security Info=True;";
        SaatSchoolEntities db = new SaatSchoolEntities(conn);

        private GenericRepository<tbl_Peoples> _peopleRepository;
        private GenericRepository<tbl_Group> _groupRepository;
        private GenericRepository<tbl_TemplateMsg> _templateMsgRepository;
        private GenericRepository<tbl_ConfClock> _confClockRepository;
.
.
.

اينم ابتداي فايل Generic

namespace DAL.Generics
{
    public class GenericRepository<TEntity> where TEntity : class
    {
        private SaatSchoolEntities _context;
        private DbSet<TEntity> _dbSet;

        public GenericRepository(SaatSchoolEntities context)
        {
            _context = context;
            _dbSet = context.Set<TEntity>();
        }

الان خطايي كه داره ميده فك كنم داره فحش ميده .  (ميگه يا از DatabaseFirst استفاده كن يا از CodeFirst)

اين از Context :

//------------------------------------------------------------------------------
// <auto-generated>
//     This code was generated from a template.
//
//     Manual changes to this file may cause unexpected behavior in your application.
//     Manual changes to this file will be overwritten if the code is regenerated.
// </auto-generated>
//------------------------------------------------------------------------------

using System.Data.Entity.Core.EntityClient;

namespace DAL
{
    using System;
    using System.Data.Entity;
    using System.Data.Entity.Infrastructure;
    
    public partial class SaatSchoolEntities : DbContext
    {
        public SaatSchoolEntities(string connectionString)
            : base(connectionString)//("name=SaatSchoolEntities")
        {
        }
    
        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            throw new UnintentionalCodeFirstException();
        }
    
        public virtual DbSet<tbl_Group> tbl_Group { get; set; }

خب از اول بگید DBFirst استفاده کردید

                Entities db=new Entities();
                db.Database.Connection.ConnectionString = "";

پوزش كه نگفتم ولي من از هر دوش استفاده كردم . dbFirst رو آوردم روي UnitOfWork و جنريك . الان با توضيح شما باز هم خطا دارم چون اگه كد بالا رو تو كانستراكتور unitofwork هم كه تعريف مي كنم نميره ازش بخونه و اول ميره سراغ app.config و چون توش connection string نيست خطا ميگيره !

نباید ابنطور باشه

باید ابتدا از کد بخونه

سرچ کنید Set Connection String EF In Code