How do I write data to a text file in C#?

Assuming you have the data already:

string path = @"C:\temp\file"; // path to file
using (FileStream fs = File.Create(path)) 
{
        // writing data in string
        string dataasstring = "data"; //your data
        byte[] info = new UTF8Encoding(true).GetBytes(dataasstring);
        fs.Write(info, 0, info.Length);

        // writing data in bytes already
        byte[] data = new byte[] { 0x0 };
        fs.Write(data, 0, data.Length);
}

(taken from msdn docs and modified)