Unity NetWorkManager and NetWorkIdentity

Hey guys,
I need some help about NetWorkIdentity
I use the code to spawn a GameObject to server
this is my code

    using UnityEngine;
    using System.Collections;
    using UnityEngine.Networking;
    using System;
     public class PlayerController : NetworkBehaviour
        {
           void FixedUpdate()
            {
                 if (isLocalPlayer)
                {
                 if (Input.GetMouseButton(0))
                    {
                        Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
                        RaycastHit hit;
        
                        if (Physics.Raycast(ray, out hit, 1000))
                        {
                            if (hit.collider.tag.Contains("box"))
                            {
                                CmdRotationServer(hit.collider.gameObject);
                            }
                        }
                    }
        
        }
        
            }
[Command]
    private void CmdSpawnToServer()
    {
        GameObject go = GameObject.Instantiate(GameObject.CreatePrimitive(PrimitiveType.Capsule), new Vector3(2, 2, 2), Quaternion.identity) as GameObject;
        go.AddComponent<NetworkIdentity>();
        go.AddComponent<CapsuleController>();
        go.name = go.name.Replace("(Clone)", "");
        manager = GameObject.FindObjectOfType<NetworkManager>();
        if (manager != null)
        {
            if (manager.spawnPrefabs.Find(p => p.GetComponent<NetworkIdentity>().assetId.Equals(go.GetComponent<NetworkIdentity>().assetId)) == null)
            {
                manager.spawnPrefabs.Add(go);
            }
        }

        NetworkServer.Spawn(go);
        Debug.Log(go.GetComponent<NetworkIdentity>().assetId);
        // this assetid is 00000000000 
    }
        }

[79184-qq截图20160929092246.png|79184]
[79185-qq截图20160929092316.png|79185]
when I pressed F1 ,it will generate the capsule on the scene
but this capsule‘s assetsid=0000000000;

i don’t understand why?
who can tell me ?
thank you ~

ps: that capsule is not a prefab !

do u solve this question ?