如何改进此排序代码？

Question

我正在检查sort参数并构建一堆if语句:

if (sortDirection == "ASC")
{
    if (sortBy == "Id")
        return customerList.OrderBy(x => x.Id).Skip(startIndex).Take(pageSize).ToList();
    if (sortBy == "FirstName")
        return customerList.OrderBy(x => x.FirstName).Skip(startIndex).Take(pageSize).ToList();
    if (sortBy == "City")
        return customerList.OrderBy(x => x.City).Skip(startIndex).Take(pageSize).ToList();
}
else
{
    if (sortBy == "Id")
        return customerList.OrderByDescending(x => x.Id).Skip(startIndex).Take(pageSize).ToList();
    if (sortBy == "FirstName")
        return customerList.OrderByDescending(x => x.FirstName).Skip(startIndex).Take(pageSize).ToList();
    if (sortBy == "City")
        return customerList.OrderByDescending(x => x.City).Skip(startIndex).Take(pageSize).ToList();
}

我该如何做得更好？

Answer 1

将您的订单和查询的其余部分分开 - 对于您不必在代码库中复制的每个查询,相同的部分(保持干燥):

var query = customerList;

if (sortDirection == "ASC")
{
    if (sortBy == "Id")
       query = query.OrderBy(x => x.Id);
    ///and so on
}

query = query.Skip(startIndex).Take(pageSize).ToList();