如何使用EntityFramework爲搜索交叉多個查詢？

Question

當人們搜索我的網站時，我不想只搜索值（q），我想用空格作爲分隔符搜索每個單詞。我編寫了大部分代碼，但有些部分我不知道該怎麼做。

你可以檢查下面的代碼中的「待辦事項」，並建議我一個辦法嗎？或者可能是一個完全不同的方法順便說一句，如果可能的話，我想保留SQL代碼的一部分，因爲它對我來說更自然，但所有的TODO都可以在LINQ中完成。

感謝

下面是代碼：

[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

下面的代碼將這樣的伎倆：

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

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

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

此外，在你的地方，我會還採取@KirkWoll的評論成帳戶並使用FullTextSearch而不是LIKE。

Answer 2

對於strQueries各str你創建按名稱排序，並存儲在List<T>明顯格式化的SQL查詢，其中T是Recipe（？）。嘗試類似的東西：

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); 

是allRecipes應該通過後類型IEnumerable<Recipe>的。

Answer 3

試試這個辦法，這將導致一個SQL語句：

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(); 
}