var fs = File.Create(name);
fs.Close();  // Important: always close the stream after use

private static void Rm()
{
    var name = Console.ReadLine();
    if (!ValidateExists(name)) return;
    File.Delete(name);
}

var content = File.ReadAllText(name);
Console.WriteLine(content);

File.AppendAllText(name, text);

FileStream fs = new FileStream(name, FileMode.OpenOrCreate, FileAccess.ReadWrite);
StreamReader sr = new StreamReader(fs);
sr.BaseStream.Seek(0, SeekOrigin.Begin);
string str = sr.ReadLine();

FileStream fs = new FileStream(name, FileMode.Create, FileAccess.ReadWrite);
StreamWriter w = new StreamWriter(fs);
w.Write(text);
w.Flush();
w.Close();
fs.Close();

private static bool ValidateExists(string? name)
{
    if (string.IsNullOrEmpty(name)) return false;
    if (!File.Exists(name)) return false;
    return true;
}