C # multi-threaded delegate delegation to read multiple files and display them in the same text box

A netizen asked: the specified directory contains several small text files, which need to be read using multiple threads. One file, one thread, or a total of 10 threads. Append all the read text to the specified edit box in the window. Only one edit box is written in this box. line feed is optional. I wrote the following solution using the delegate Method: Using system; using system. collections. generic; using system. componentmodel; using system. data; using system. drawing; using system. text; using system. windows. forms; using system. io; using system. threading; namespace multithread {public partial class form1: FORM {public form1 () {initializecomponent ();} private void button#click (Object sender, eventargs E) {using (folderbrowserdialog FBD = new folderbrowserdialog () {FBD. description = "select the path for multi-threaded File Reading"; FBD. shownewfolderbutton = false; If (FBD. showdialog (this) = dialogresult. OK) {directoryinfo di = new directoryinfo (FBD. selectedpath); foreach (fileinfo fi in Di. getfiles ("*. TXT ") {thread t = new thread (this. invokethread); T. start (Fi. fullname) ;}}} private delegate void readfile (Object filepath); Private void invokethread (Object filepath) {If (this. invokerequired) {This. invoke (New readfile (readfilecontent), filepath);} else {readfilecontent (filepath) ;}} private void readfilecontent (Object filepath) {This. textbox1.appendtext (file. readalltext (filepath. tostring (), encoding. default); this. textbox1.appendtext ("\ r \ n ");}}}