[英]ASP.NET MVC5. I don't know why my form returns null viewmodel object
[英]Don't include .Where() if variable is null ASP.NET MVC
我有這個功能:
public List<PostIndexResponse> GetPosts(string search, int? categoryId)
{
var currentUserId = HttpContext.Current.User.Identity.GetUserId() ?? "";
var srch = search ?? "";
var posts = _set.Where(x => x.PersonId.Contains(currentUserId) && x.Description.Contains(srch) && x.CategoryId == categoryId).OrderByDescending(x => x.CreatedOn)).ToList();
return posts;
}
僅當categoryId
不為空時,我才想要x.CategoryId == categoryId
。 如何在沒有 if else 條件的情況下執行此操作並基於它是否為空創建另一個查詢?
我會把它分成幾行像這樣(未經測試)......
這允許您有條件地過濾categoryId
,我認為它比嘗試將其全部塞進單個表達式更清潔和更易於維護。 無需創建 2 個重疊表達式
public List<PostIndexResponse> GetPosts(string search, int? categoryId)
{
var currentUserId = HttpContext.Current.User.Identity.GetUserId() ?? "";
var srch = search ?? "";
var query = _set.Where(x => x.PersonId.Contains(currentUserId) && x.Description.Contains(srch));
if (categoryId.HasValue)
query = query.Where(x => x.CategoryId == categoryId);
var posts = query.OrderByDescending(x => x.CreatedOn)).ToList();
return posts;
}
另一種選擇是將x.CategoryId == categoryId
替換為
(categoryId == null || x.CategoryId == categoryId)
但這種表達方式已經變得越來越長,難以維持。
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