C#

txtOutput.Lines = sorted;

string[] data = File.ReadAllLines(@"D:\Temp\MyLargeTextFile.txt");
Stopwatch s1 = new Stopwatch();
Stopwatch s2 = new Stopwatch();
s1.Start();
textBox1.Lines = data;
s1.Stop();
s2.Start();
StringBuilder sb = new StringBuilder();
foreach (string s in data)
    {
    sb.Append(s);
    sb.Append("\r\n");
    }
textBox2.Text = sb.ToString();
s2.Stop();
Console.WriteLine("{0} lines: {1}/{2}", data.Length,s1.Elapsed, s2.Elapsed);

22777 lines: 00:00:01.5580246/00:00:01.5555734

x: 
dt←$DateTime:Now;
 sb←#new $StringBuilder ⍬;
 {sb:AppendLine (⍵:ToString)}¨⍳x;
 ($DateTime:Now)-dt 

builder.AppendFormat("{0}\r\n", s);

List<string> sl = new List<string> { "wo", "ab", "c"};

sl.Sort();

textBox1.Lines = sl.ToArray();

public DataTable function(int myTableKey)
{
  string msg;
  try
  {
     DataTable dt;
     //some coding... with success
      return dt;
  }
  catch(Exception ex)
  {
      msg = ex.Message;
      return msg; //now here I dont know what to do
  }
}

catch(Exception ex)
{
     //either throw it;
     throw;
     //or log it and make the dt null
     dt = null;
}
return dt;

try
{
}
catch (Exception ex)
{
    throw ex;
}

try { ... }
catch(Exception) { throw; }