lista de c# a cadena
List<string> names = new List<string>() { "John", "Anna", "Monica" };
string result = string.Join(",", names.ToArray());
c# lista de convertir a string
string combindedString = string.Join( ",", myList.ToArray() );
c# cadena de generación de lista de cadenas
string.Join(", ", stringCollection); // "Value1, Value2, Value3