如何将多个查询与 EntityFramework 相交以进行搜索？

Question

当人们搜索我的网站时，我不想只搜索值 (q)，我想用空格作为分隔符搜索每个单词。我已经编写了大部分代码，但有些部分我不知道该怎么做。

你能检查下面代码中的“todo”并建议我一个方法吗？或者也许是一种完全不同的方法。顺便说一句，如果可能的话，我想保留 SQL 代码部分，因为这对我来说更自然，但所有 TODO 都可以在 LINQ 中完成。

谢谢

代码如下：

[HttpPost]
        public ActionResult Search(string q)
        {
            ViewBag.q = q;

            String[] strQueries = q.Split(' ');

            //TODO: Create an array of type var???

            foreach (string str in strQueries)
            {
                var recipesTemp = db.Recipes.SqlQuery(
                String.Format(
                "SELECT * FROM Recipe WHERE Name LIKE '%{0}%' " +
                "UNION ALL " +
                "SELECT * FROM Recipe WHERE IDRecipe IN ( " +
                "    SELECT IDRecipe FROM Subtitle WHERE Name LIKE '%{0}%') " +
                "UNION ALL  " +
                "SELECT * FROM Recipe WHERE IDRecipe IN ( " +
                "    SELECT IDRecipe FROM RecipeTag " +
                "        INNER JOIN Tag ON Tag.IDTag = RecipeTag.IDTag  " +
                "    WHERE Name LIKE '%{0}%') " +
                "UNION ALL   " +
                "SELECT * FROM Recipe WHERE IDRecipe IN ( " +
                "    SELECT IDRecipe FROM Subtitle " +
                "        INNER JOIN Ingredient ON Ingredient.IDSubtitle = Subtitle.IDSubtitle  " +
                "    WHERE QuantityAndName LIKE '%{0}%')", str)).Distinct().OrderBy(r => r.Name).ToList();

                //TODO: Add recipesTemp to the array of var
            }

            var recipes = //TODO: INTERSECT the results from all the recipesTemp in the array of type var

            return View("Search", recipes);
        }

Answer 1

下面的代码可以解决问题：

        var selectedRecipies = new List<IEnumerable<Recipy>>();

        foreach(...)
        {
            ...
            selectedRecipies.Add(recipesTemp);
        }

        var recipies = selectedRecipies.Aggregate((a, i) => a.Intersect(i));

此外，在您的位置上，我还会考虑 @KirkWoll 的评论并使用 FullTextSearch 而不是 LIKE。

Answer 2

对于strQueries 中的每个str，您将创建一个按名称排序并存储在List<T> 中的不同格式的SQL 查询，其中T 是Recipe (?)。试试这样的：

var allRecipes = strQueries.Select(str => db.Recipes.SqlQuery(
    String.Format(
        "SELECT * FROM Recipe WHERE Name LIKE '%{0}%' " +
        "UNION ALL " +
        "SELECT * FROM Recipe WHERE IDRecipe IN ( " +
        "    SELECT IDRecipe FROM Subtitle WHERE Name LIKE '%{0}%') " +
        "UNION ALL  " +
        "SELECT * FROM Recipe WHERE IDRecipe IN ( " +
        "    SELECT IDRecipe FROM RecipeTag " +
        "        INNER JOIN Tag ON Tag.IDTag = RecipeTag.IDTag  " +
        "    WHERE Name LIKE '%{0}%') " +
        "UNION ALL   " +
        "SELECT * FROM Recipe WHERE IDRecipe IN ( " +
        "    SELECT IDRecipe FROM Subtitle " +
        "        INNER JOIN Ingredient ON Ingredient.IDSubtitle = Subtitle.IDSubtitle  " +
        "    WHERE QuantityAndName LIKE '%{0}%')", str)).Distinct().OrderBy(recipe => recipe.Name))
    .SelectMany(recipe => recipe);

之后allRecipes 应该是IEnumerable<Recipe> 类型。

Answer 3

试试这个方法，它会产生一条 SQL 语句：

var names = q.Split(' ');

if(names.Any())
{
    var firstName = names[0];

    var query = context.Recipes.Where (q => q.Name.Contains(firstName));
    // other unions ...
    // query = query.Union( context.Recipes.Where (...
    foreach (var name in names.Skip(1))
    {
        query = query.Union(context.Recipes.Where (q => q.Name.Contains(name)));
        // other unions ...
        // query = query.Union( context.Recipes.Where (...
    }

    // query evaluated now
    var recipes = query.ToList();
}