linq到实体：无效父母的模式

发布于 2025-01-21 11:46:44 字数 1209 浏览 2 评论 0原文

我正在查询一个实体框架模型，因此在这种情况下，我将LINQ用于实体。这只是意味着我无法使用所有最新的操作员。

这是一个Linq选择语句：

            var nodes = r.Find(pn =>
                pn.StatusId == PageStatus.Active &&
                pn.IncludeInSitemap &&
                sitemap.Contains(pn.PageTemplate.SiteSectionId))
                .Select(x => new
                {
                    x.PageTemplate.RouteName,
                    x.RouteValues,
                    x.PageTemplate.PhysicalFile,
                    MetaLastModified = x.PageMeta.LastModified,
                    ContentBlock = x.PageContent != null
                        ? x.PageContent.ContentBlock
                        : default,
                    ContentLastModified = x.PageContent != null
                        ? x.PageContent.LastModified
                        : default,
                    x.PageType.Priority
                })
                .OrderByDescending(x => x.Priority)
                .ThenBy(x => x.RouteName)
                .ToList();

如您所见，我有两个属性，需要检查PageContent并非零。我无法使用“？”操作员是因为它是实体的linq。但是，我想知道是否有可能对父进行零检查（而不是两个）并相应地设置两个属性。

Linq对我来说有点陌生，因此这可能是一个非常简单的答案或不可能的。

任何建议都感谢。

原文

I'm querying an Entity Framework model, so In this case, I'm using LINQ to Entities. It just means I can't use all of the latest operators.

Here's a LINQ select statement:

            var nodes = r.Find(pn =>
                pn.StatusId == PageStatus.Active &&
                pn.IncludeInSitemap &&
                sitemap.Contains(pn.PageTemplate.SiteSectionId))
                .Select(x => new
                {
                    x.PageTemplate.RouteName,
                    x.RouteValues,
                    x.PageTemplate.PhysicalFile,
                    MetaLastModified = x.PageMeta.LastModified,
                    ContentBlock = x.PageContent != null
                        ? x.PageContent.ContentBlock
                        : default,
                    ContentLastModified = x.PageContent != null
                        ? x.PageContent.LastModified
                        : default,
                    x.PageType.Priority
                })
                .OrderByDescending(x => x.Priority)
                .ThenBy(x => x.RouteName)
                .ToList();

As you can see, I have two properties where I need to check PageContent is not null. I can't make use of the "?" operator because it is LINQ to Entities. However, I wondered if it is possible to do the NULL check on the parent once (instead of the two) and set both properties accordingly.

LINQ is a bit alien to me, so it could be a very simple answer or impossible.

Any advice appreciated.

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挥剑断情 2025-01-28 11:46:44

这样的东西？

                .Select(x => new
                {
                    x.PageTemplate.RouteName,
                    x.RouteValues,
                    x.PageTemplate.PhysicalFile,
                    MetaLastModified = x.PageMeta.LastModified,
                    PageContent = x.PageContent
                    x.PageType.Priority
                })
             .Select(anonymousClass => 
                         anonymousClass.PageContent is PageContentType pg ? 
                                  new { ... } : 
                                  new {})

如果我们用真实类替换匿名类...那么构造函数可以进行一次测试，您需要确保正确设置推论属性...

something like this ?

                .Select(x => new
                {
                    x.PageTemplate.RouteName,
                    x.RouteValues,
                    x.PageTemplate.PhysicalFile,
                    MetaLastModified = x.PageMeta.LastModified,
                    PageContent = x.PageContent
                    x.PageType.Priority
                })
             .Select(anonymousClass => 
                         anonymousClass.PageContent is PageContentType pg ? 
                                  new { ... } : 
                                  new {})

if we replace the anonymous class by a real class... then the constructor can have the one time test you want to assure the deduced properties are correctly set...

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