Here is one approach
Create an enum
enum Number
{
zero,
one,
two,
three,
four,
five,
six,
seven,
eight,
nine,
}
Read each character from the string and get its corresponding text from enum
string Text = "";
string value = "01234";
for (int i = 0; i < value.Length; i++)
{
Text += (Number)(int.Parse(value.Substring(i, 1))) + " ";
}
Console.WriteLine(Text);