C ＃ display the list control, select the file to obtain the file path and filter the file extension, and RichTextBox displays the data

https://www.cnblogs.com/wllhq/p/4330766.htmllistview Show database data articles
https://www.cnblogs.com/qc-id-01/p/7489021.html Select file and filter file extensions

private void button2_Click(object sender, EventArgs e)
        {
    
            OpenFileDialog P_File_Folder = new OpenFileDialog();
             P_File_Folder.Multiselect = true;// This value determines whether multiple files can be selected 
             P_File_Folder.Title = " Please select a folder ";
             P_File_Folder.Filter = "QQ.db(QQ.db)|QQ.db";
             if (P_File_Folder.ShowDialog() == System.Windows.Forms.DialogResult.OK)
                {
    
                    string file = P_File_Folder.FileName;
                    wenpath = file;
                    Console.Write(file);
                }

https://www.cnblogs.com/arxive/p/5725570.htmlrichtextbox use