Linq不包含“哪里"的定义 [英] Linq does not contain the definition for 'Where'

问题描述

我正尝试通过if语句来调整查询，如下所示:

I'm trying to adjust my query through an if statement as shown below:

        IQueryable articles = null;

        if (User.IsInRole("Admin"))
        {
            articles = from s in db.Articles
                       select s;
        }
        if (User.IsInRole("Educator"))
        {
            articles = from s in db.Articles
                       where s.createdBy == WebSecurity.CurrentUserName
                       select s;

        }

这似乎没有给我任何错误.但是，当我尝试使用where子句进行更多过滤时，它无法识别该术语.我知道IQuerable不支持它，但是有一种方法可以将最初的文章"设置为null，然后使用if语句进行设置?

This doesn't seem to give me any errors. However, when I try to filter a bit more with a where clause it doesn't recognize the term. I understand IQuerable doesn't support it, but is there a way to originally set "articles" to null, then set it with a if statement?

if (!String.IsNullOrEmpty(searchString))
        {
            articles = articles.Where(s => s.title.ToUpper().Contains(searchString.ToUpper())
                                   || s.content.ToUpper().Contains(searchString.ToUpper()));
        }
        switch (sortOrder)
        {
            case "name_desc":
                articles = articles.OrderByDescending(s => s.title);
                break;
            case "Date":
                articles = articles.OrderBy(s => s.dateCreated);
                break;
            case "date_desc":
                articles = articles.OrderByDescending(s => s.dateCreated);
                break;
            case "rating_desc":
                articles = articles.OrderByDescending(s => s.finalReview);
                break;
            case "Rating":
                articles = articles.OrderBy(s => s.finalReview);
                break;
            case "Views":
                articles = articles.OrderBy(s=>s.numViews);
                break;
            case "views_desc":
                articles = articles.OrderByDescending(s => s.numViews);
                break;
            case "Educators":
                articles = articles.OrderBy(s => s.educatorCRUD);
                break;
            case "educators_desc":
                articles = articles.OrderByDescending(s => s.educatorCRUD);
                break;
            default:
                articles = articles.OrderBy(s => s.title);
                break;
        }

我知道我可以在if语句if(User.IsInRole("Admin"))中执行此操作，然后执行所有代码，然后将同一代码复制并粘贴到不同的if语句中(if(user.IsInRole("Educator ))，但我认为这是多余且非常糟糕的编码做法.

I know I can do this in a big if statment if(User.IsInRole("Admin")) then execute all code then copy and paste the same code in a different if statement (if(user.IsInRole("Educator)), but I think this redundant and really bad coding practice.

干杯.

推荐答案

您的articles变量正在使用非通用类型IQueryable，该类型的支持实际上很少.

Your articles variable is using the non-generic type IQueryable, which supports very little indeed.

您想要IQueryable<T>作为合适的<T>.例如:

You want IQueryable<T> for a suitable <T>. For example:

IQueryable<Article> articles;
// Initialize as before

不过，我会亲自更改您的初始化方式:

I'd personally change how you're initializing it though:

IQueryable<Article> articles = db.Articles;
if (User.IsInRole("Admin"))
{
    // No change...
}
else if (User.IsInRole("Educator"))
{
    articles = articles.Where(s => s.createdBy == WebSecurity.CurrentUserName);
}
else
{
    // Throw an exception? What do you want to happen if they're neither an
    // educator nor an administrator?
}

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