问C#中如何将对象转换为Dictionary <TKey，TValue>？

public static void MyMethod(object obj)
{
    if (typeof(IDictionary).IsAssignableFrom(obj.GetType()))
    {
        // My object is a dictionary, casting the object:
        // (Dictionary<string, string>) obj;
        // causes error ...
    }
    else
    {
        // My object is not a dictionary
    }
}