C# custom file extension filter

Question

I'm trying to read a list of documents in a directory. I understand how the filter modifiers work at a high level and have used them before. However, this time I need to filter something that doesn't have a standardized extension (i.e. "*.txt" or *.pdf").

I'm using the example as found on.... https://docs.microsoft.com/en-us/dotnet/api/system.windows.forms.filedialog.filter?view=net-5.0

 using System;

using System.Windows.Forms;

namespace COMS2412_Readin
{
    public partial class Form1 : Form
    {
        string Serial_num = null;
        string INI_file_dir_temp = null;
        string CONFIG_data = null; 
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            //Allow user to enter serial number and load it for useage later. 
            Serial_num = Serial_number_text.Text;
            try
            {
                using (OpenFileDialog COMS_file_dialog = new OpenFileDialog())
                {
                    COMS_file_dialog.InitialDirectory = "c:\\";
                    //Have dialog box filter out all files without the .INI extention. 
                    COMS_file_dialog.Filter = "txt files (*.INI)|*.INI|All files (*.*)|*.*"; //Failed
                    //                    COMS_file_dialog.Filter = "*.INI"; //Failed
                    //                    COMS_file_dialog.Filter = "(*.INI)"; //Failed
                    //                    COMS_file_dialog.Filter = "(INI files | *.INI)"; //Failed
                    COMS_file_dialog.FilterIndex = 2;
                    COMS_file_dialog.RestoreDirectory = true;
                    if (COMS_file_dialog.ShowDialog() == DialogResult.OK)
                    {
                        //Check to make sure it was the correct file type. 
                        INI_file_dir_temp = COMS_file_dialog.FileName;
                    }
                }
            }
            catch
            {
                //Sorry there was an error with opening the file. Please ensure the file is not currently open. 
            }
        }
    }
}

The project I'm working on imports config files from an external piece of equipment. The problem is there are literally thousands of files, each with unusual file extensions. For example *.INI is one of the extensions I want to filter. I've tried just entering `*.INI as the argument but it didn't work. What am I missing? Is there a way to alter...

openFileDialog.Filter = "txt files (*.txt)|*.txt|All files (*.*)|*.*";

to filter specific file extensions?

Answer 1

Finally, have something that works...

openFileDialog.Filter = "(*.INI)|*.INI";

This filters out everything that isn't of the .INI extension. For me specifically, I had to run VS as admin and ensure the files were not hidden.