1、普通查找：双层循环遍历，第二层循环中找到即break，查找时间复杂度O(M*N/2)

List
      
        cameraList = new List
       
        ();List
        
          cameraIdList = dataIds.Split(',').ToList();List
         
           oldList = this.cameraList.Cameras.ToList();for (int i = 0; i < cameraIdList.Count; i++){    string cameraId = cameraIdList[i];    for (int j = 0; j < _cameraList.Count; j++)    {        PtCameraInfo camera = _cameraList[j];        if (camera.ID == cameraId && !oldList.Exists(a => a.ID == camera.ID))        {            cameraList.Add(camera);            break;        }    }}
         
        
       
      

2、高效查找：排序虽然费时，但数量级低，所以耗时很低，排序时间复杂度O(M*logM+N*logN)，查找过程也是双层循环，但第二层循环比较省时，查找时间复杂度O(M*logN)，总的时间复杂度：O(M*logM+N*logN+M*logN)

List
      
        cameraList = new List
       
        ();List
        
          cameraIdList = dataIds.Split(',').ToList();List
         
           oldList = this.cameraList.Cameras.ToList();//排序this._cameraList.Sort(new Comparison
          
           ((a, b) =>{    return string.Compare(a.ID.PadLeft(36, '0'), b.ID.PadLeft(36, '0'));}));cameraIdList.Sort((a, b) =>{    return string.Compare(a.PadLeft(36, '0'), b.PadLeft(36, '0'));});//高效查找int k = 0;for (int i = 0; i < cameraIdList.Count; i++){    string cameraId = cameraIdList[i];    for (int j = k; j < _cameraList.Count; j++)    {        PtCameraInfo camera = _cameraList[j];        if (camera.ID == cameraId && !oldList.Exists(a => a.ID == camera.ID))        {            cameraList.Add(camera);            k = j;            break;        }    }}
          
         
        
       
      

说明：cameraList的数量级是2万，当cameraIdList数量从1到大约1000时，高效查找耗时始终是0.1秒多左右，而普通查找，当cameraIdList数量很少时，很快，0.05秒，当cameraIdList数量接近1000时，大约2秒。