How use Transaction in EntityFramework 5?

Add reference to System.Transactions, import using System.Transactions; and then try to encapsulate your code by

using (gasstationEntities ctx = new gasstationEntities(Resources.CONS))
{
   using (var scope = new TransactionScope())
   {
      [... your code...]

      scope.Complete();
   }
}

If exception occurs, scope.Complete() is not called and the rollback is automatic.

EDIT : I've just seen your MySql tag. If this doesn't work, have a look here !

Try this, Technically, the using should commit the transaction when there are no exceptions, but in case of exception, the using will automatically rollback it.

using (var txn = new TransactionScope())
{
    ctx.Database.ExecuteSqlCommand("truncate table tb_expensesall");
    ctx.Database.ExecuteSqlCommand("truncate table tb_wholesale");
    ctx.Database.ExecuteSqlCommand("truncate table tb_singlesale");
    ctx.Database.ExecuteSqlCommand("truncate table tb_purchase");
    txn.Complete();
}
new MessageWindow(this, Resources.GetString("Warn"), Resources.GetString("DeleteSuccess"));