how to create multi thread in c++/cli windows form

Question

 Hi, i have created windows form in c++/cli. In my form i used listbox, textbox and button. so when i press button following function should execute....

but am getting cross thread error.... please give me a solution

error:

HResult=0x80131509
  Message=Cross-thread operation not valid: Control 'listBox1' accessed from a thread other than the thread it was created on.

              ///program///

 public: void print_notification()
{

this->listBox1->Items->Add(this->textBox1->Text);
}

 public: void print_output()
{
this->listBox2->Items->Add(this->textBox1->Text);
}

private: System::Void button1_Click(System::Object^  sender, System::EventArgs^  e)
         {

             ThreadStart^ ThreadMethod1 = gcnew ThreadStart(this, &MyForm::print_notification);
             ThreadStart^ ThreadMethod2 = gcnew ThreadStart(this, &MyForm::print_output);
             Thread^ MyThread1 = gcnew Thread(ThreadMethod1);
             Thread^ MyThread2 = gcnew Thread(ThreadMethod2);
             MyThread1->Start();
             MyThread2->Start();

          }

 

Answer 1

Try this:

void Add1( )

{

   listBox1->Items->Add( textBox1->Text );

}

 

void print_notification( )

{

   Invoke( gcnew System::Action( this, &MyForm::Add1 ) );

}

 

I.e. use Invoke (or BeginInvoke sometimes) to access the controls from threads.

Adjust the second thread too.

 

Answer 2

Thank you...its working and how can i set priorities to these threads???

Answer 3

[...] how can i set priorities to these threads???

Try something like this:

   MyThread1->Priority = ThreadPriority::Lowest;

Or, inside thread procedure:

   Thread::CurrentThread->Priority = ThreadPriority::Lowest;