Question

I’ve written this method to cast a comma separated string into a List of its type:

public List<T> GetListFromString<T>(string commaSplited)
{
  return commaSplited.Split(',').Cast<T>().ToList();
}

But it throws an exception saying ‘The specified cast is not valid.’
I’ve tested it with long input.

Answer 1

Your code certainly works if T is string (I tested it).

If T is something else, say int, you will get this Exception.

This Works

List<string> result = GetListFromString<string>("abc, 123, hij");

This Fails

List<int> resultInt = GetListFromString<int>("23, 123, 2");

That is because one cannot cast or convert string to int, e.g. the following would fail too:

int three = (int)"3";

The Fix

public List<T> GetListFromString<T>(string commaSplited)
    {
        return (from e in commaSplited.Split(',') 
                select (T)Convert.ChangeType(e, typeof(T))).ToList();
    }

However all of the given strings must be convertable to T, e.g. the following would still fail:

List<int> resultIntFail = GetListFromString<int>("23, abc, 2");

because “abc” cannot be converted to type int.

Also, T must be some type that System.Convert() knows how to convert to from a string.