C#: How do you split a string after a specific length and after a whitespace?

This might be a really dumb question for some of you, but I just don't seem to get this right: I want to divide a long string into some lines of text. Therefore I need to split it after a specific length. As the words should be complete in one line it should also take care of the whitespaces. And there's the problem!

This is my code:

for(x=0; x<Text.Length; x+=CharsInOneLine)

{

if( !(x+CharsInOneLine > Text.Length) )

{

StringArray[ x / CharsInOneLine ] = Text.Substring (x , CharsInOneLine);

}

}

else

[...]

This code correctly splits the string into parts. But of course it does not take care of the whitespaces. And: No, I can't use \r\n to create a new line. It does not work in this specific case.

Can anyone of you help?