Question

In C# I know this

 if (textBox1.Text.Length > x)
    {
        textBox1.AppendText(Environment.NewLine);
    }

(x is some random number)
But what if I want to break on first space before x?

Answer 1

I think your question is:

I want to insert a new line at a space closest to “x” where the space’s index does not exceed “x”.

So given this example:

The quick brown box jumped over the lazy dog.

And “X” is 30, then I would expect a new line to be inserted between “jumped” and “over”.

I think this is something that would work for you:

var str = "The quick brown box jumped over the lazy dog.";
var x = 30;
var index = str.Select((c, i) => new {c, i}).TakeWhile(q => q.i < x).Where(q => q.c == ' ' ).Select(q => q.i).Last();
var formatted = str.Insert(index, Environment.NewLine);

Where formatted contains the new string with the line-break. Note that Last() will give an exception if there are no spaces in the string at all. In that case, use LastOrDefault and handle appropriately.

So given your example:

var x = 30;
if (textBox1.Text.Length > x) 
{
    var index = textBox1.Text.Select((c, i) => new {c, i}).TakeWhile(q => q.i < x).Where(q => q.c == ' ' ).Select(q => q.i).Last(); 
    textBox1.Text = textBox1.Text.Insert(index, Environment.NewLine);
}