how to take distinct values from table from foreign key in mvc razor

Question

When Iam doing a project i got confused in a place to retrieve only unique value from table. for that i distinct , groupby clauses in the linq query, but I got some error . I have two tables and the id of category table is foreign key and I need to retrieve only distinct id from the another gallery table

model

public partial class Gallery
{
    public int Id { get; set; }
    public int CategoryId { get; set; }
    public string ImageTitle { get; set; }
    public string Image { get; set; }

    public virtual Category Category { get; set; }
}




   public Category()
    {
        this.Galleries = new HashSet<Gallery>();
    }

    public int Id { get; set; }
    public string CategoryName { get; set; }

    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
    public virtual ICollection<Gallery> Galleries { get; set; }
}

this is the model the categoryid is the foreign key to the gallery class

controller

   public ActionResult GalleryCata()
    {
        var res = db.Galleries.ToList();
        return View(res);
    }

view

 @model List<ThaniyamBank.Models.Gallery>

  @for (var j = 0; j < Model.Count(); j++)
        {
            <div class="col-lg-3 col-md-3 col-sm-3 col-xs-12">
                <div class="hovereffect">
                    <img src="@Url.Content("~/GalleryImages/" + @Html.DisplayFor(m => m[j].Image))" class="img-responsive" alt="" />
                    <div class="overlay">
                        <h2>@Html.DisplayFor(m => m[j].Category.CategoryName) </h2>
                        <a class=" fancybox info " href="@Url.Content("~/GalleryImages/" + @Html.DisplayFor(m => m[j].Image))" data-fancybox-group="gallery"><i class="fa fa-eye" aria-hidden="true"></i></a>
                        <a class="info " href="gallery.html"><i class="fa fa-link" aria-hidden="true"></i></a>
                    </div>
                </div>
            </div>
        }

I need to display the images based on the category. when i run the application i get all the images from the table and not by based on the category . can anyone please help me to solve the problem ??

I don't see any "distinct , groupby". Show what you tried, which will probably clarify what you mean by "unique". And show the error. "I got some error" doesn't mean much. — Gert Arnold
when I give var res = db.Galleries.Select(x=>x.CategoryId).Distinct().ToList(); in controller, got the error The model item passed into the dictionary is of type 'System.Collections.Generic.List1[System.Int32]', but this dictionary requires a model item of type 'System.Collections.Generic.List1[A.Models.Gallery]'. — user256
by changing list to ienumerable shows the error Cannot apply indexing with [] to an expression of type 'IEnumerable<Gallery>'. If i just write db without list and ienumerable then how can i get the collection of data from table ?? — user256

Georg Patscheider Georg Patscheider · Accepted Answer · 2017-02-28T11:29:56

Select tells EF to retrieve a certain value, so db.Galleries.Select(x=>x.CategoryId) returns a collection of integer, therefore you get the error message.

What you want is to use a Where clause:

var res = db.Galleries.Where(x => x.CategoryId == selectedCategoryId).ToList();

which returns IList<Gallery>. You will need to pass int selectedCategoryId to your action.

Distinct is only needed if you expect that the same Gallery is contained in the same Category multiple times.

how to take distinct values from table from foreign key in mvc razor

1 Answers