int MessageBox(
   LPCTSTR lpszText,
   LPCTSTR lpszCaption = NULL,
   UINT nType = MB_OK 
);

void CMainFrame::OnDisplayErrorMessage()
{
   // This displays a message box with the title "Error"
   // and the message "Help, Something went wrong."
   // The error icon is displayed in the message box, along with
   // an OK button.
   MessageBox(_T("Help, Something went wrong."), _T("Error"), 
      MB_ICONERROR | MB_OK);
}

MFC Alert MessageBox

MessageBox 클래스

.NET Framework (current version)

다른 버전

private:
   void validateUserEntry()
   {
      // Checks the value of the text.
      if ( serverName->Text->Length == 0 )
      {
         // Initializes the variables to pass to the MessageBox::Show method.
         String^ message = "You did not enter a server name. Cancel this operation?";
         String^ caption = "No Server Name Specified";
         MessageBoxButtons buttons = MessageBoxButtons::YesNo;
         System::Windows::Forms::DialogResult result;

         // Displays the MessageBox.
         result = MessageBox::Show( this, message, caption, buttons );
         if ( result == ::DialogResult::Yes )
         {
            // Closes the parent form.
            this->Close();
         }
      }
   }

private:
   void Form1_FormClosing(Object^ sender, FormClosingEventArgs^ e)
   {
	  // If the no button was pressed ...
      if ((MessageBox::Show(
         "Are you sure that you would like to close the form?", 
         "Form Closing", MessageBoxButtons::YesNo, 
         MessageBoxIcon::Question) == DialogResult::No))
      {
		 // cancel the closure of the form.
         e->Cancel = true;
      }
   }

c# dll ClassLibrary 에서 MessageBox.Show(text,title);

c# dll 을 만들다가

c#의 MessageBox를 사용하고 싶을때가 있다.

그럴때는

바로

using System.Windows.Forms;

하면 안 되고

System.Windows.Forms 을 참조 해주어야한다.

VS2013

[프로젝트이름]우클릭 -> [추가] -> [참조] -> [어셈블리] -> [프레임워크] -> [System.Windows.Forms] 를 체크해주면 해당 라이브러리를 자동으로 참조해준다.

그 다음 

using System.Windows.Forms;

를 쓰고

MessageBox.Show("mySocket is Null", "strTitle");