How to save listbox to existing text file with date

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C#

So im trying to figure out for alot of hours how i can make it save my listbox items in a existing file.

So basically what my program does is ; whenever i click the start button it creates a folder name with date... inside the folder it creates 2 text files "good" & "bad"..

So whenever something is good it should put it in the listbox1. when i press a button i want to it save it automatically to the text file.

// create folder
           string myDate = DateTime.Today.ToString(" [yyyy-MM-dd]");
           DateTime now1 = new DateTime();
           now1 = DateTime.Today;
           string today = now1.ToString();
           Directory.CreateDirectory("Results" + myDate);
           File.WriteAllText(Path.Combine("Results" + myDate, "Good.txt"), "");
           File.WriteAllText(Path.Combine("Results" + myDate, "Bad.txt"), "");

save button (empty atm because nothing worked)

private void button9_Click(object sender, EventArgs e)
        {

        }

What I have tried:

i tried streamwriter but everytime it denies the folder or it cant find, and i dont really know how to implement a folder with date inside the code to make it find.

in my "checking" script at the end of "working" script it will perform automatically a click on the button9 to make it save after each working proxy.

This is basically the idea.