Linq 中的拼接条件

  public IQueryable<BBS_Theme> GetListPage(int PageSize, int PageIndex, NameValueCollection nvcParamWhere, NameValueCollection nvcorderby, ref int AllCount)
        {
			#region where
			var searchPredicate = PredicateExtensions.True<BBS_Theme>();
            if (nvcParamWhere != null)
            {
                foreach (string key in nvcParamWhere)
                {
                    string condition = string.Empty;
                    switch (key)
                    {
                        #region
						case "ID":
                            condition = nvcParamWhere[key];
                            searchPredicate = searchPredicate.And(u => u.ID.Equals(condition));
                            break;
						case "LableID":
                            condition = nvcParamWhere[key];
                            searchPredicate = searchPredicate.And(u => u.LableID.Equals(condition));
                            break;

			
						
                        default:
                            break;

                        #endregion
                    }
                }
            }
			#endregion
			
			#region queryable
            var linq = (from a in db.BBS_Theme
                        select a)
						.Where(searchPredicate);
			#endregion 
			
			#region orderby
            if (nvcorderby != null)
            {
                foreach (string key in nvcorderby)
                {
                    string condition = string.Empty;

                    switch (key)
                    {
						case "ID":
                            condition = nvcorderby[key];
                            if(bool.Parse(condition))
							{
                            	linq = linq.OrderBy(o=>o.ID);
							}
							else
							{
                                linq = linq.OrderByDescending(o => o.ID);
							}
                            break;
						//........省略n个case
						
                        default:
                            break;

                    }
                }
            }
			#endregion
			
			AllCount = linq.Count();
            linq = linq.Skip(PageSize * (PageIndex - 1)).Take(PageSize);
            return linq;
        }