How to split string preserving whole words?

Question

I need to split long sentence into parts preserving whole words. Each part should have given maximum number of characters (including space, dots etc.). For example:

Answer 1

At first I was thinking this might be a Regex kind of thing but here's my shot at it:

List parts = new List();
int partLength = 35;
string sentence = "Silver badges are awarded for longer term goals. Silver badges are uncommon.";

string[] pieces = sentence.Split(' ');
StringBuilder tempString = new StringBuilder("");

foreach(var piece in pieces)
{
    if(piece.Length + tempString.Length + 1 > partLength) 
    {
        parts.Add(tempString.ToString());
        tempString.Clear();        
    }
    tempString.Append(" " + piece); 
}