Multi Spaces should convert in to single space

public static string NormalizeWhiteSpace(string S)

{

string s = S.Trim();

bool iswhite = false;

int sLength = s.Length;

StringBuilder sb = new StringBuilder(sLength);

foreach (char c in s.ToCharArray())

{

if (Char.IsWhiteSpace(c))

{

if (iswhite)

{

continue;

}

else

{

sb.Append(" ");

iswhite = true;

}

}

else

{

sb.Append(c.ToString());

iswhite = false;

}

}

return sb.ToString();

}