C# 无法将类型“XXXX.Classes.Idophalen”隐式转换为“System.Collections.IEnumerable”

Question

I making a project where I need to run an query and get that answer in a list into a Datagrid.

Here is my code: Main:

        public UserControlDetails(string Id)
    {
        InitializeComponent();
        var db = new Database();
        var QueriAnswer = db.GetArtikel(Id);
        DGVoedingswaarden.ItemsSource = QueriAnswer;
    }

db.GetArtikel(Id):

        public Idophalen GetArtikel(string id)
    {
        using (var conn = new MySqlConnection(ConnectionString))
        {

                conn.Open();
                var query = "SELECT naam FROM tb_product WHERE Id = '" + id + "'";
                var SelectArtikel = new MySqlCommand(query, conn);
                var reader = SelectArtikel.ExecuteReader();

                while (reader.Read())
                {
                    var Id = reader.GetString(0);
                    var artikel = new Idophalen(Id);
                    return artikel;
                }
        }
        return null;
    }

Idophalen ( In English: GetId )

   public  class Idophalen
{
    public string Id { get; set; }

    public Idophalen(string Id)
    {
        this.Id = Id;
    }
    public override string ToString()
    {
        return string.Format("{0}", Id);
    }


}

So the problem is that the code ( DGVoedingswaarden.ItemsSource = QueriAnswer; the error: Cannot implicitly convert type 'XXXX.Classes.Idophalen' to 'System.Collections.IEnumerable'. gives. So I don't know how to fix this or what it means. The other posts on Stackoverflow did not help me so here my case.

If you need more explanation please leave a comment

Answer 1

Your GetArtikel method returns a single Idophalen . The ItemsSource property of an ItemsControl can only be set to an IEnumerable such as a List<Idophalen> . So you may create a list that contains only the single object returned from the database:

DGVoedingswaarden.ItemsSource = new List<Idophalen>(1) { QueriAnswer };

Answer 2

The ItemsSource property accepts only an IEnumerable. GetArtikel() returns an Idophalen which is not an IEnumerable instance.

you can create a list and add the result to it but it really is not a good solution. you should reconsider what you are trying to do is plausible.

anyways, this should make it work:

var QueriAnswer = db.GetArtikel(Id);
DGVoedingswaarden.ItemsSource = new List<Idophalen>() { QueriAnswer };