C# StringBuilder: Check if it ends with a new line

Question

I have a StringBuilder that accumulates code. In some cases, it has 2 empty lines between code blocks, and I'd like to make that 1 empty line.
How can I check if the current code already has an empty line at the end? (I prefer not to use its ToString() method because of performance issues.)

Answer 1

You can access any character of your StringBuilder with its index, like you would with a String.

var sb = new StringBuilder();
sb.Append("Hello world!\n");
Console.WriteLine(sb[sb.Length - 1] == '\n'); // True

Answer 2

You can normalize the newlines, using a regex:

var test = @"hello

moop

hello";

var regex = new Regex(@"(?:\r\n|[\r\n])+");

var newLinesNormalized = regex.Replace(test, Environment.NewLine);

output:

hello
moop
hello

Answer 3

Single line check. Uses a string type, not StringBuilder, but you should get the basic idea.

if (theString.Substring(theString.Length - Environment.NewLine.Length, Environment.NewLine.Length).Contains(Environment.NewLine))
{
     //theString does end with a NewLine
}
else
{
     //theString does NOT end with a NewLine
}