conversion

int[] i=configurationsetting.appsettings["i"].split(',');

The use of the Split method implies configurationsetting.appsettings["i"] is a string.
The Split method returns an array of strings.
So you would need to loop through each string and convert it to an int, then store those in an array if that is how you want to access them.

string[] strings = configurationsetting.appsettings["i"].Split(',');
int[] numbers = new int[strings.Length];
for (int i = 0; i < strings.Length; i++)
    {
    int.TryParse(strings[i], out numbers[i]);
    }