public void GetAllProducts()
 {
     ProductDropDownList.DataSource     = _PurchaseRepository.GetAllProducts();
     ProductDropDownList.DataTextField  = "Name";
     ProductDropDownList.DataValueField = "Id";
     ProductDropDownList.DataBind();
     ProductDropDownList.Items.Insert(0, new System.Web.UI.WebControls.ListItem("Select Products", "0"));
 }