当密钥基于多个标识属性时，优化字典以进行比较

I have the following code:

我有以下代码:

if (!this._masterAccountDefinitions.ContainsKey(
     outletName.ToLower(CultureInfo.CurrentCulture) + "/" +
     officeName.ToLower(CultureInfo.CurrentCulture))
   ) {
     //Add new item to list
}
if (!thi