Question

I have a file created from a directory listing. From each of item a user selects from a ListBox, the application reads the directory and writes out a file that matches all the contents. Once that is done it goes through each item in the ListBox and copies out the item that matches the ListBox selection. Example:

Selecting 0001 matches:

• 0001456.txt
• 0001548.pdf.

The code i am using isn’t handling 0s very well and is giving bad results.

var listItems = listBox1.Items.OfType<string>().ToArray();
var writers = new StreamWriter[listItems.Length];
for (int i = 0; i < listItems.Length; i++)
{
    writers[i] = File.CreateText(
        Path.Combine(destinationfolder, listItems[i] + "ANN.TXT"));
}
var reader = new StreamReader(File.OpenRead(masterdin + "\\" + "MasterANN.txt"));

string line;
while ((line = reader.ReadLine()) != null)
{
    for (int i = 0; i < listItems.Length; i++)
    {
        if (line.StartsWith(listItems[i].Substring(0, listItems[i].Length - 1)))
            writers[i].WriteLine(line);
    }
}

Advice for correcting this?

Another Sample:
I have 00001 in my listbox: it returns these values:
00008771~63.txt
00002005~3.txt
00009992~1.txt
00001697~1.txt
00000001~1.txt
00009306~2.txt
00000577~1.txt
00001641~1.txt
00001647~1.txt
00001675~1.txt
00001670~1.txt

It should only return:
00001641~1.txt
00001647~1.txt
00001675~1.txt
00001670~1.txt
00001697~1.txt

Or if someone could just suggest a better method for taking each line in my listbox searching for line + “*” and whatever matches writes out a textfile…

Answer 1

This is all based pretty much on the one example you gave, but I believe the problem is that when you are performing your matching, you are getting the substring if your list item value and chopping off the last character.

In your sample you are attempting to match files starting with “00001”, but when you do the match you are getting substring starting at zero and value.length-1 characters, which in this case would be “0000”. For example:

string s = "00001";
Console.WriteLine(s.Substring(0,s.Length-1));

results in

0000

So I think if you just changed this line:

if (line.StartsWith(listItems[i].Substring(0, listItems[i].Length - 1))) 
            writers[i].WriteLine(line);

to this

if (line.StartsWith(listItems[i]))
            writers[i].WriteLine(line);

you would be in good shape.