ASP.NET MVC getting Distinct Values From Database using LINQ

Question

I am trying to get the ID and name of multiple objects from my database when a user submits a form. I don't want any repeats though when it displays the results.

I have my Form:

@using (Html.BeginForm("Advancedresults", "Search", FormMethod.Post))
        {
            {
                foreach (var r in ViewBag.res)
                {
                    string hes = r.iname;
                    <div class="col-md-4">
                        @Html.CheckBox("drink", false, new { value = hes })
                        @r.iname
                    </div>
                }
                <input type="submit" />
            }
        }

This is sent to my Search Controller using the HttpPost Method:

[HttpPost]
    public ActionResult Advancedresults()
    {
        string drinks = Request.Form["drink"];
        List<string> dList = drinks.Split(',').ToList();
        dList = dList.Where(x => x != "false").ToList();
        List<string> r = new List<string>();

        foreach (string st in dList)
        {

            r.AddRange(from a in db.Recipes.AsEnumerable()
                       join b in db.RecipeIngredients on a.ID equals b.recipe_id
                       join i in db.Ingredients on b.ingredient_id equals i.id
                       join u in db.Measures on b.measure_id equals u.id
                       where i.name.Equals(st)
                       select a.name
                      );
        }

        List<string> ra = new List<string>();

        foreach (string ras in r)
        {
            if (!ra.Contains(ras))
            {
                ra.Add(ras);
            };
        }


        ViewBag.Ingredients = ra.ToList();
        return View();
    }

Is there a better way of adding the ID and name to the ViewBag? I know what I am doing now is not best practice.

TheGeneral · Accepted Answer · 2018-10-31 03:35:31Z

2

You could probably simplify it by using Contains and Distinct

var results = (from a in db.Recipes.AsEnumerable()
           join b in db.RecipeIngredients on a.ID equals b.recipe_id
           join i in db.Ingredients on b.ingredient_id equals i.id
           join u in db.Measures on b.measure_id equals u.id
           where dList.Contains(i.name)
           select a.name ).Distinct();

ViewBag.Ingredients = results.ToList();

answered Oct 31, 2018 at 3:35

TheGeneral

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Eleazpogi · Accepted Answer · 2018-10-31 04:01:26Z

You can use the Distinct() method of LINQ to select unique values from a list. Example:

List<string> ra = new List<string>(r.Distinct());

Regarding to your question if you can add both Name and ID to the ViewBag, I suggest for you to use Dictionary:

Dictionary<int, string> Results = new Dictionary<int, string>();

Given that, you can update your LINQ query to something like this:

var results = (from a in db.Recipes.AsEnumerable()
       join b in db.RecipeIngredients on a.ID equals b.recipe_id
       join i in db.Ingredients on b.ingredient_id equals i.id
       join u in db.Measures on b.measure_id equals u.id
       where dList.Contains(i.name).GroupBy(a => a.ID, a=>a.Name).ToDictionary(s=>s.Key, v=>v.First());

ViewBag.Ingredients = results.ToList();

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