Question

Following scheme works fine dealing with strings/primitives. But when dealing with lists it gives type cast error in getObj(). The types used are dynamic and needs this generic use.
Is there any better way to achieve it ?

public static Object obj;
    static public T getObj<T>()
    {
        return (T)obj;
    }
    private static string getStr()
    {
        return "some string";
    }
    private static List<Object> getList()
    {
        List<Object> res = new List<object>();
        Object o = "str1";
        res.Add(o);

        o = "str2";
        res.Add(o);
        return res;
    }

    public static void Main()
    {
        obj = getStr();
        string s = getObj<string>();

        obj = getList();
        List<string> slist = getObj<List<string>>();
    }

Answer 1

You’re trying to cast a List<Object> to a List<String>. Even if all the contents of the list are of String, the List is still a List<Object>, so you cannot do a direct cast like that.

If you really want to do so, you could use this instead:

List<Object> objList = { ... }; // all strings
List<String> strList = objList.Cast<String>().ToList();

A reason you cannot do a cast from List<Object> to List<String> is because all strings are objects but not all objects are strings; if you casted a List<String> to List<object> and then tried to add an object (that is not a string) to it, the behaviour would be undefined.