private void AddSourceFile(VsaEngine engine, string filename){
IVsaCodeItem item;
string name = "$SourceFile_" + this.codeItemCounter++;
item = (IVsaCodeItem)engine.Items.CreateItem(name, VsaItemType.Code, VsaItemFlag.None);
item.SetOption("codebase", filename);
item.SourceText = this.ReadFile(filename, engine);
}