我有一个具有三个Where
子句的LINQ查询。在每个Where
子句中,我都在查找同一组项目以比较值:
var items = _umbracoHelper.GetPage(ItemsPage.ModelTypeAlias).Children
.Where(x => level1Category == 0 || x
.GetPropertyValue<IEnumerable<IPublishedContent>>(UmbracoAlias.Item.Categories)
.Select(y => y.Id).Contains(level1Category))
.Where(x => !level2Categories.Any() || x
.GetPropertyValue<IEnumerable<IPublishedContent>>(UmbracoAlias.Item.Categories)
.Select(y => y.Id).Intersect(level2Categories.AsEnumerable()).Any())
.Where(x => !level3Categories.Any() || x
.GetPropertyValue<IEnumerable<IPublishedContent>>(UmbracoAlias.Item.Categories)
.Select(y => y.Id).Intersect(level3Categories.AsEnumerable()).Any());
有没有一种方法可以一次获取UmbracoAlias.Items.Categories的值并将该值存储在其他where子句中,而又不会导致GetPropertyValue方法执行一次以上?
最佳答案
您可以将每个项目与类别ID配对,如下所示:
var items = _umbracoHelper.GetPage(ItemsPage.ModelTypeAlias).Children
.Select(c => new {
Child = c
, CategoryIds = c
.GetPropertyValue<IEnumerable<IPublishedContent>>(UmbracoAlias.Item.Categories)
.Select(y => y.Id)
.ToList()
})
.Where(x => level1Category == 0 || x.CategoryIds.Contains(level1Category))
.Where(x => !level2Categories.Any() || x.CategoryIds.Intersect(level2Categories.AsEnumerable()).Any())
.Where(x => !level3Categories.Any() || x.CategoryIds.Intersect(level3Categories.AsEnumerable()).Any())
.Select(x => x.Child);
这将对与子类别ID配对的子项进行过滤,然后仅将
Child
对象保留在最终投影中。您可以通过组合所有三个
Where
子句来进一步简化此操作:var items = _umbracoHelper.GetPage(ItemsPage.ModelTypeAlias).Children
.Where(c => {
var categoryIds = c
.GetPropertyValue<IEnumerable<IPublishedContent>>(UmbracoAlias.Item.Categories)
.Select(y => y.Id)
.ToList();
if (level1Category != 0 && !categoryIds.Contains(level1Category)) {
return false;
}
if (level2Categories.Any() && !categoryIds.Intersect(level2Categories.AsEnumerable()).Any()) {
return false;
}
if (level3Categories.Any() && !categoryIds.Intersect(level3Categories.AsEnumerable()).Any()) {
return false;
}
return true;
});
关于c# - 在多个linq Where子句中使用相同的查找值,而不必查找多次,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/49335839/