"worker-id" option is supported in versions >= 2.6.2.0 so download recent miner version from here and edit "worker-id" in pools section in config.json file.
one more thing "worker-id" value must match pattern( length [1 : 8] , contains lowercase or uppercase latin letters or symbol _ )  
if you still face any problem please let me know.
[/quote]


I did it like this. but nothing happens. still the same. and I was using the 2.6.2.0 what do I wrong. do I have to change more?
{                                                                                                             
    "algo": "cryptonight-webchain",
    "av": 0,                // algorithm variation, 0 auto select                                             
    "background": false,    // true to run the miner in the background                                       
    "colors": true,         // false to disable colored output                                               
    "cpu-affinity": null,   // set process affinity to CPU core(s), mask "0x3" for cores 0 and 1             
    "cpu-priority": null,   // set process priority (0 idle, 2 normal to 5 highest)                           
    "donate-level": 5,      // donate level, mininum 1%                                                       
    "log-file": null,       // log all output to a file, example: "c:/some/path/webchain-miner.log"           
    "max-cpu-usage": 100,    // maximum CPU usage for automatic mode, usually limiting factor is CPU cache not this option.                                                                                                 
    "print-time": 60,       // print hashrate report every N seconds                                         
    "retries": 5,           // number of times to retry before switch to backup server                       
    "retry-pause": 5,       // time to pause between retries                                                 
    "safe": false,          // true to safe adjust threads and av settings for current CPU                   
    "syslog": false,        // use system log for output messages                                             
    "threads": null,        // number of miner threads                                                           
    "pools": [
        {
            "url": "pool.webchain.network:3333", // URL of mining server
            "user": "0x404337b1548755443fd3ea93ced2bb5cdb047ba4",               // username for mining server
            "pass": "xxxxxxx",                         // password for mining server
            "worker-id": "PC01",                    // worker ID for mining server
            "keepalive": false,                  // send keepalived for prevent timeout (need pool support)
            "nicehash": false
        }
    ],
    "api": {
        "port": 0,                             // port for the miner API https://github.com/xmrig/xmrig/wiki/API
        "access-token": null,                  // access token for API
        "worker-id": null                      // custom worker-id for API
    }
}