Trying to make a txt file of a list using a webpart

I'm using a sandboxed solution, this is the error i got when i try to make the txt

Request for the permission of type 'System.Security.Permissions.FileIOPermission, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' failed. sharepoint

This is the code I have for creating and writting on the file

string path = @"C:\pruebas\" + txtNombre.Text + ".txt";
        if (!File.Exists(path))
        {
            using (StreamWriter sw = File.CreateText(path))//here happens the error
            {
                sw.WriteLine("Hello");
                sw.WriteLine(Texto);
            }
        }
        using (StreamReader sr = File.OpenText(path))
        {
            string s = "";
            while ((s = sr.ReadLine()) != null)
            {
                Console.WriteLine(s);
            }
        }