Composite Keys組合鍵Entityentities-with-composite-keysDefine the primary key b.HasKey(c => new {c.FormId, c.OptionId}); 注意沒設定主鍵的話，會出現以下錯誤： The entity type 'User' requires a primary key to be defined. Define the foreign keycomposite foreign key12 February 2026Rider PluginFK