Language issue while saving a string into database using entity framework

I have an aspx page with a textbox and button. When I clicked button, it's sending textbox's text to a function and saves it to database using entity framework. The issue is when I use my local characters in textbox such as ş, ğ, ı, ö , ü, these characters are saved as s, g, i, o, u. What is the problem?

My codes (Product.aspx)

 <asp:TextBox ID="txtTitle" runat="server"></asp:TextBox> 
 <asp:Button ID="btnUpdate" runat="server" Text="Update" OnClick="btnUpdate_Click" />

(Product.aspx.cs)

 protected void btnUpdate_Click(object sender, EventArgs e)
    {
        Product p = new Product ()
        {
            Id = Int32.Parse(Session["ProductId"].ToString()),
            Title = txtTitle.Text
        };
        int productId = ProductManager.UpdateProduct (p);
        if (productId != -1)
        {
            // SUCCESS
        }
        else
        {
             // ERROR
        }
    }


  public static int UpdateProduct(Product product)
    {
        using (var context = new LidyaEntities())
        {
            Product pUpd = context.Product.FirstOrDefault(p => p.Id == product.Id);
            if (pUpd != null)
            {
                pUpd.Title = product.Title;
            }
            return context.SaveChanges();
        }
    }

Database table (SQL SERVER);

  (Id, int)
  (Title, text)