从SQL到LINQ的转换

Question

SELECT * FROM Recipe WHERE ID IN 
    (SELECT RID FROM Recipe_Ingredient WHERE IID IN 
           (SELECT MIN(ID) FROM Ingredients WHERE Name IN('broccoli','egg')))

I am trying to translate this sql query into linq. So far I got no luck.

I receive a string array of ingredients. So far I got to this:

List<string> searchList = new List<string>(search);
var ing = context.Ingredients.Where(x => x.Name.Contains(searchList.ToString())).ToList();
var recing = context.Recipe_Ingredients.Where(x => ing.Contains(x.IID)).Select(x => x.IID).ToList();
var rec = context.Recipes.Where(x => recing.Contains(x.ID)).ToList();

But by using the debugger it fails on the ing because the searchList is not contained in x.Name ( searchList[0] = 'egg' when I use it for testing)

Answer 1

You have small mistake in ing line. And first 2 ToList methods are redundant.

List<string> searchList = new List<string>(search);
var ing = context.Ingredients.Where(x => searchList.Contains(x.Name));
var recing = context.Recipe_Ingredients.Where(x => ing.Contains(x.IID)).Select(x => x.IID);
var rec = context.Recipes.Where(x => recing.Contains(x.ID)).ToList();

Answer 2

You are not translating the MIN(...) in the SQL.

var searchList = new List<string>(search); // broccoli, egg
var recipies = context.Recipes
    .Where(r =>
        context.Recipe_Ingredients
            .Where(ri =>
                context.Ingredients
                    .Where(i => searchList.Contains(i.Name))
                    .Select(i => i.ID)
                    .Min() == ri.IID
            )
            .Select(ri => ri.RID)
        .Contains(r.ID)
    )
    .ToList();

Answer 3

1. You're inverting the Contains (you're not doing an in clause)
2. Min(Id) can't be a list (in your sql query), it will be a unique id.
3. Don't put ToList() too early, it will generate multiple queries.

So to stay near your code, you could do

List<string> searchList = new List<string>(search);
var ingId = context.Ingredients.Where(x => searchList.Contains(x.Name)).Min(m => m.Id);
var recing = context.Recipe_Ingredients.Where(x => x.IID == ingId).Select(x => x.RID);
var rec = context.Recipes.Where(x => recing.Contains(x.ID)).ToList();