Question

I have this requirement,

A product can have multiple images and only one default image. You can determine the default image of the product if the property isDefault is equal to true.

I want to do it in LINQ and lambda but I’m stucked in my code:

private class ProdcutImages
{
    public Int32 ID { get; set; }
    public String ProductID { get; set; }
    public Boolean IsDefault { get; set; }
    public Image Image { get; set; }
    public String FileName { get; set; }
}

public void SetDefaultImage(int productID)
{
    SqlConnection conn = getConnection();
    conn.Open();
    SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM product_images WHERE product_id = @ID", conn);
    da.SelectCommand.Parameters.Add(new SqlParameter("@ID", productID));


    DataTable dt = new DataTable();
    da.Fill(dt);

    var imageList = (from tr in dt.AsEnumerable()
                        select new ProdcutImages()
                        {
                            ID = tr.Field<int>("id"),
                            ProductID = tr.Field<string>("productId"),
                            IsDefault = tr.Field<bool>("isDefault"),
                            Image = tr.Field<Image>("image"),
                            FileName = tr.Field<string>("fileName")
                        }).ToList();

    pictureBox1.Image = // ???
    conn.Close();
}

Answer 1

probably this:

var img = imageList.FirstOrDefault(i => i.IsDefault);
if (img != null) { pictureBox1.Image = img.Image; }

or, to take into account the case someone forgot to set the IsDefault field on any image:

var img = imageList.FirstOrDefault(i => i.IsDefault) ?? imageList.FirstOrDefault();
if (img != null) { pictureBox1.Image = img.Image; }

(this would use the first available image if none is set as default)