Read and Write Text in a file in C#

The WriteAllText creates a new file, writes the contents to the file and then closes the file. If a file already exists, then this method overwrites it.
The ReadAllText opens a text file, reads all lines of the file into a string, and then closes the file.

string fileName = @"C:\Temp\Mahesh.txt";          
if (!File.Exists(fileName))
{
    string startText = "Here is a file content" + Environment.NewLine;
    File.WriteAllText(fileName, startText);
    File.WriteAllText(fileName, "Add more content \n");
}
string appendText = "New appened text" + Environment.NewLine;
File.AppendAllText(fileName, appendText);
string data = File.ReadAllText(fileName);
Console.WriteLine(data)