missing assembly reference

[boyosof]

CS0234: The type or namespace name 'ShoppingCart' does not exist in the namespace 'MyWebsite.Commerce' (are you missing an assembly reference?)\[code\]public class ProfileCommon : System.Web.Profile.ProfileBase { public virtual MyWebsite.Commerce.ShoppingCart Cart { get { return ((MyWebsite.Commerce.ShoppingCart)(this.GetPropertyValue("Cart"))); } set { this.SetPropertyValue("Cart", value); } } public virtual string Country { get { return ((string)(this.GetPropertyValue("Country"))); } set { this.SetPropertyValue("Country", value); } } public virtual string Gender { get { return ((string)(this.GetPropertyValue("Gender"))); } set { this.SetPropertyValue("Gender", value); } } public virtual int Age { get { return ((int)(this.GetPropertyValue("Age"))); } set { this.SetPropertyValue("Age", value); } } public virtual ProfileCommon GetProfile(string username) { return ((ProfileCommon)(ProfileBase.Create(username))); }}\[/code\]when i run this page the an error occured and when i clicked the error line it goes to above code please anyone help me ASAP please.......