分享一个 EF6 分页查询数据的 IQueryable 扩展方法

/// <summary>
/// 由其它 Reponsitory 提供数据源，分页查询数据
/// </summary>
/// <typeparam name="T"></typeparam>
/// <typeparam name="S"></typeparam>
/// <param name="source"></param>
/// <param name="pageIndex"></param>
/// <param name="pageSize"></param>
/// <param name="whereLambda"></param>
/// <param name="orderbyLambda"></param>
/// <param name="total"></param>
/// <param name="isAsc"></param>
/// <returns></returns>
public static List<T> FindPageList<T, S>(this IQueryable<T> source, int pageIndex, int pageSize, Expression<Func<T, bool>> whereLambda, Expression<Func<T, S>> orderbyLambda, out int total, bool isAsc)
{
  total = source.Where(whereLambda).Count();
  List<T> result;
  if (isAsc)
  {
    result = source
      .Where(whereLambda)
      .OrderBy(orderbyLambda)
      .Skip(pageSize * (pageIndex - 1))
      .Take(pageSize)
      .ToList();
  }
  else
  {
    result = source
     .Where(whereLambda)
     .OrderByDescending(orderbyLambda)
     .Skip(pageSize * (pageIndex - 1))
     .Take(pageSize)
     .ToList();
  }
  return result;
}

/// <summary>
/// 使用动态拼接 OrderBy 语句，分页查询数据
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="source"></param>
/// <param name="pageIndex"></param>
/// <param name="pageSize"></param>
/// <param name="whereLambda"></param>
/// <param name="orderbyExpression"></param>
/// <param name="total"></param>
/// <returns></returns>
public static List<T> FindPageList<T>(this IQueryable<T> source, int pageIndex, int pageSize, Expression<Func<T, bool>> whereLambda, string orderbyExpression, out int total)
{
  total = source.Where(whereLambda).Count();
  var result = source
    .Where(whereLambda)
    .OrderBy(orderbyExpression)
    .Skip(pageSize * (pageIndex - 1))
    .Take(pageSize)
    .ToList();
  return result;
}

public List<T> QueryPageList<S>(int pageIndex, int pageSize, Expression<Func<T, bool>> whereLambda, Expression<Func<T, S>> orderbyLambda, out int total, bool isAsc)
{
  var source = _dbContext.Set<T>().AsNoTracking().AsQueryable();
  var result = source.FindPageList(pageIndex, pageSize, whereLambda, orderbyLambda, out total, isAsc);
  return result; 
}
public List<TB01Dto> QueryPageList(QueryPageParams queryPageParams, out int total)
{
  Expression<Func<TB01, bool>> whereLambda = a => !a.STSHT01.Equals("D", StringComparison.OrdinalIgnoreCase);
  if (!string.IsNullOrEmpty(queryPageParams.SearchKeyword))
  {
    Expression<Func<TB01, bool>> second = (a => a.NAMEHT01.Contains(queryPageParams.SearchKeyword) || a.COMPHT01 == queryPageParams.SearchKeyword);
    whereLambda = whereLambda.And(second);
  }
  var list = QueryPageList(queryPageParams.PageIndex, queryPageParams.PageSize, whereLambda, (a => a.COMPHT01), out total, queryPageParams.IsAsc);
  var result = CommonUtil.TranObject2OtherType<List<TB01Dto>>(list);
  return result;
}

public List<UserMenuDTO> QueryPageList(QueryPageParamsForuserMenu queryPageParams, out int total)
{
   var query = userMenuReposition.QueryMenuUsers(queryPageParams.MenuUserName);
   
   Expression<Func<UserMenuDTO, bool>> whereLambda = a => true;
   
   if (queryPageParams.CompanyCodes != null && queryPageParams.CompanyCodes.Length > 0)
   {
    Expression<Func<UserMenuDTO, bool>> second = (a => queryPageParams.CompanyCodes.Contains(a.COMPHT03));
    whereLambda = whereLambda.And(second); 
   }
   
   var list = query.FindPageList(queryPageParams.PageIndex, queryPageParams.PageSize, whereLambda, "COMPHT03, MNUCDHT03", out total);
   
   return list;
}