a question about SystemVerilog randomize

sorry, I can't type Chinese.
below is one segment of my code:
"
class cfg_mc_c extends cfg_base_c;
   //public properties
   typedef enum {LONG=0, SHORT=1, NONE=2} DLY_TP;
   rand DLY_TP   rw_delay_type;
   rand int unsigned rw_delay_max;      //ns
   rand int unsigned rw_delay_min;
   rand int unsigned rw_delay;
   //empty test constraints
   constraint c_test1;
   constraint c_test2;
   constraint c_test3;
   //defined constraints
   constraint c_type2range    {
        if (rw_delay_type == LONG) {
                rw_delay_max == 200;
                rw_delay_min == 100;
                }
        else if (rw_delay_type == SHORT) {
                rw_delay_max == 50;
                rw_delay_min == 10;
                }
        else {
                rw_delay_max == 0;
                rw_delay_min == 0;
                }
        }
   constraint c_range2delay    {
        rw_delay inside {[rw_delay_min:rw_delay_max]};
        }
"
my intention is:
1. if the tester DOESN'T specify the rw_delay_type, then all of the variable will be randomized according to the constraint;
2. if the tester specify the rw_delay_type, then the variables except "rw_delay_type" will be randomized according to the constraints.
there is no problem with 1. but if I want to specify the rw_delay_type by below means:
"
env.cfg.mc.rw_delay_type.rand_mode(0);   //disable the random for dly_tp
env.cfg.mc.rw_delay_type = 1;                     //specify the value for dly_tp
"
such error message I got:
"
Error-[CNST-CIF] Constraints inconsistency failure
/proj/xxxx/data/rave/shared/private/mc_model_c.sv, 132
  Constraints are inconsistent and cannot be solved.
  Please check the inconsistent constraints being printed above and rewrite
  them.
"
Help me PLEASE

如果你想指定的话，不用rand_mode(0)也可以啊，直接.randomize with {...=1;}不就行了
另外，有依赖关系的约束大概 加上solve...before比较好，你两个约束块都加上这个试试

将
env.cfg.mc.rw_delay_type.rand_mode(0);   //disable the random for dly_tp
env.cfg.mc.rw_delay_type = 1;         //specify the value for dly_tp
改为
env.cfg.mc.randomize_with {delay_type == cfg_mc_c::SINGLE};