Remove comma and add comma in string in c#

//remove comman and add comma

string department = "Support, Integration, Developer";

string dptment = "";

string[] dpt = department.Split(',');

for (int i = 0; i <= dpt.Length - 1; i++)

{

if (i == dpt.Length - 1)

{

dptment = dptment + dpt[i];

}

else

{

dptment = dptment + dpt[i] + ", ";

}

}

Console.WriteLine(dptment);

//remove comma and add without comman in list

List<string> lsttype = new List<string>();

string[] extracttype = department.Split(',');

for (int i = 0; i <= extracttype.Length - 1; i++)

{

lsttype.Add(extracttype[i]);

}

Console.WriteLine(lsttype.ToList());