Please try to do something like this....
SqlCommand sqlcmd = new SqlCommand("DELETE FROM Loan_Trans WHERE IDNO =@IDNO AND ID_CODE = @ID_CODE AND TRANS_NO = @TRANS_NO",sqlcon);
sqlcmd.Parameters.Add(new SqlParameter("@IDNO",txt_Actual_Loan_No.Text));
sqlcmd.Parameters.Add(new SqlParameter("@ID_CODE", txt_Id_Code.Text));
sqlcmd.Parameters.Add(new SqlParameter("@TRANS_NO", txt_Transaction_No.Text));
OR
sqlcmd.Parameters.Add("@IDNO", SqlDbType.Text).Value = txt_Actual_Loan_No.Text;
sqlcmd.Parameters.Add("@ID_CODE", SqlDbType.Text).Value = txt_Id_Code.Text;
sqlcmd.Parameters.Add("@TRANS_NO", SqlDbType.Text).Value = txt_Transaction_No.Text;
sqlcmd.ExecuteNonQuery();