//File and path you want to create and write to
string fileName = @"C:TempTemp.txt";
//Check if the file exists
if (!File.Exists(fileName))
{
// Create the file and use streamWriter to write text to it.
//If the file existence is not check, this will overwrite said file.
//Use the using block so the file can close and vairable disposed correctly
using (StreamWriter writer = File.CreateText(fileName))
{
writer.WriteLine("Hello World");
}
}