Question

以下关于排序的代码有什么问题？命中排序代码，但排序从不应用于结果。

var results = new List<Location>();

var county = context.boc_County.Where(x => x.Description.Contains(phrase.ToLower())).ToList();
results.AddRange(_mapper.MapCountyFromDb(county));

var town = context.boc_Town.Where(x => x.Description.Contains(phrase.ToLower())).ToList();
results.AddRange(_mapper.MapTownFromDb(town));

if (orderBy == "Identifier")
{
    if (direction == "ASC")
        results = results.OrderBy(x => x.Identifier);
    else
        results = results.OrderByDescending(x => x.Identifier);
}

if (orderBy == "Type")
{
    if (direction == "ASC")
        results = results.OrderBy(x => x.LocationType.ToString());
    else
        results = results.OrderByDescending(x => x.LocationType.ToString());
}

if (orderBy == "Description")
{
    if (direction == "ASC") 
        results = results.OrderBy(x => x.Description);
    else
        results = results.OrderByDescending(x => x.Description);
}

var model = new LocationSearchResult()
{
    Locations = query.Skip(page * pageSize).Take(pageSize),
    TotalCount = query.Count()
};
return model;

Answer 1

OrderBy和OrderByDescending不会更改来电者，而是会返回新的IQueryable / IEnuemrable。您必须将其分配回另一个（或相同的）变量。否则打电话给他们是没有意义的。

因为您正在使用List<T>，所以您必须添加额外的ToList()调用才能使其编译并正常工作：

if (orderBy == "Identifier")
{
    if (direction == "ASC")
        results = results.OrderBy(x => x.Identifier).ToList();
    else
        results = results.OrderByDescending(x => x.Identifier).ToList();
}
// (...)

或者您可以改为使用List<T>.Sort：

if (orderBy == "Identifier")
{
    if (direction == "ASC")
        results.Sort((x1, x2) => x1.Compare(x2));
    else
        results.Sort((x1, x2) => x2.Compare(x1));
}

IQueryable排序不起作用

1 个答案: