static void Main(string[] args)
{
    var list = new List<MyObj>
    {
        new MyObj { TransType = "Credit", PaymentMethod = 1, Amount = 1000 },
        new MyObj { TransType = "Debit", PaymentMethod = 2, Amount = 2000 },
        new MyObj { TransType = "Debit", PaymentMethod = 1, Amount = 4000 },
        new MyObj { TransType = "Credit", PaymentMethod = 3, Amount = 3000 }
    };

    var filtered = from o in list
                   where o.TransType == "Credit"
                   select new
                   {
                      o.TransType,
                      o.PaymentMethod,
                      o.Amount,
                      Credit = "<VALUE>",
                      Debit = "<VALUE>"
                   };
}
class MyObj
{
    public string TransType { get; set; }
    public int PaymentMethod { get; set; }
    public int Amount { get; set; }
}