Myujth

I created 2 buttons, one for start a new thread, the other to end it. The actual calculation inside the new thread involved new and delete so I don't abort the thread directly, but using a flag to end it. It may take some time to end the delete and result-saving, so I want the main thread to wait for the new thread to end. But however I tried, I find the new thread doesn't run(though its ThreadState is running) until the command lines for the stop-button are conducted. System::Threading::Thread works quite different from thread to me. Is it how it should be?

#include "stdafx.h"

ref class Form1 : System::Windows::Forms::Form

public:
//define a thread name and a flag to terminate the thread
System::Threading::Thread^ th1;
static bool ITP1=0;

Form1(void)
InitializeComponent();

System::Windows::Forms::Button^ ButtonStart;
System::Windows::Forms::Button^ ButtonStop;
System::Windows::Forms::Label^ Label1;

void InitializeComponent(void)

 this->SuspendLayout();

 this->ButtonStart = gcnew System::Windows::Forms::Button();
 this->ButtonStart->Location = System::Drawing::Point(20, 20);
 this->ButtonStart->Click += gcnew System::EventHandler(this, &Form1::ButtonStart_Click);
 this->Controls->Add(this->ButtonStart);

 this->ButtonStop = gcnew System::Windows::Forms::Button();
 this->ButtonStop->Location = System::Drawing::Point(120, 20);
 this->ButtonStop->Click += gcnew System::EventHandler(this, &Form1::ButtonStop_Click);
 this->Controls->Add(this->ButtonStop);

 this->Label1 = gcnew System::Windows::Forms::Label();
 this->Label1->Location = System::Drawing::Point(20, 80);
 this->Controls->Add(this->Label1);

 this->ResumeLayout(false);
 

void ThreadStart()

 for (int idx=0;idx<999999999;++idx)
 
 if (ITP1) break;
 
 this->Label1->Text = "finished";
 ITP1=0;


System::Void ButtonStart_Click(System::Object^ sender, System::EventArgs^ e)

 th1 = gcnew System::Threading::Thread(gcnew System::Threading::ThreadStart(this,&Form1::ThreadStart));
 th1->Start();
 this->Label1->Text = "running";


System::Void ButtonStop_Click(System::Object^ sender, System::EventArgs^ e)

 if (th1->ThreadState==System::Threading::ThreadState::Running)
 
 //use the flag to stop the thread
 ITP1=1;
 //the wait method using while+sleep doesn't work
 while (th1->ThreadState==System::Threading::ThreadState::Running) System::Threading::Thread::Sleep(1000);
 //replacing the wait method above with "th1->Join()" doesn't work either
 

;

int main()

Form1^ A1 = gcnew Form1();
A1->ShowDialog();
return 0;

You have to join() the called thread in the main thread. Then the main thread will wait until the called thread is finished.

See the documentation for Join to know how it is to be called.

Finally I found the cause. It's just the "this->" pointer in the new thread. Removing it makes everything OK.
I suppose it's because the Form allows operation on only one element at the same time. I ask the button-click to wait for the new thread, and the new thread tries to edit the other form element. They wait for each other to end and cause a dead loop.