无法转换Dictionary <string，dictionary <string，string>＆gt;到IDictionary <string，idictionary <string，string>＆gt; </string，idictionary <string，string> </string，dictionary <string，string>

Question

IDictionary<string, IDictionary<string, string>> test = new Dictionary<string, Dictionary<string, string>>();

此转换是错误的，为什么不能隐式Dictionary<string,Dictionary<string,string>> to IDictionary<string,IDictionary<string,string>>?

Answer 1

查看此博客"Generic type parameter variance in the CLR"，其中解释了为何不允许转化。