protected override void WndProc(ref Message m)
{
if (m.Msg == NativeMethods.WM_COPYDATA)
{
// Extract the file name
NativeMethods.COPYDATASTRUCT copyData = (NativeMethods.COPYDATASTRUCT)Marshal.PtrToStructure(m.LParam, typeof(NativeMethods.COPYDATASTRUCT));
int dataType = (int)copyData.dwData;
if (dataType == 2)
{
string fileName = Marshal.PtrToStringAnsi(copyData.lpData);
// Add the file name to the edit box
richTextBox1.AppendText(fileName);
richTextBox1.AppendText("\r\n");
}
else
{
MessageBox.Show(String.Format("Unrecognized data type = {0}.", dataType), "SendMessageDemo", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
}
else
{
base.WndProc(ref m);
}
}
static void Main(string[] args)
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
// Get the filename if it exists
string fileName = "test 2";
if (args.Length == 1)
{
fileName = args[0];
}
// If a mutex with the name below already exists,
// one instance of the application is already running
bool isNewInstance;
Mutex singleMutex = new Mutex(true, "MyAppMutex", out isNewInstance);
if (isNewInstance)
{
// Start the form with the file name as a parameter
Form1 frm = new Form1(fileName);
Application.Run(frm);
}
else
{
string windowTitle = "SystemTrayApp";
windowTitle = "SendMessage Demo";
// Find the window with the name of the main form
IntPtr ptrWnd = NativeMethods.FindWindow(null, windowTitle);
if (ptrWnd == IntPtr.Zero)
{
MessageBox.Show(String.Format("No window found with the title '{0}'.", windowTitle), "Program", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
else
{
IntPtr ptrCopyData = IntPtr.Zero;
try
{
// Create the data structure and fill with data
NativeMethods.COPYDATASTRUCT copyData = new NativeMethods.COPYDATASTRUCT();
copyData.dwData = new IntPtr(2); // Just a number to identify the data type
copyData.cbData = fileName.Length + 1; // One extra byte for the \0 character
copyData.lpData = Marshal.StringToHGlobalAnsi(fileName);
// Allocate memory for the data and copy
ptrCopyData = Marshal.AllocCoTaskMem(Marshal.SizeOf(copyData));
Marshal.StructureToPtr(copyData, ptrCopyData, false);
// Send the message
NativeMethods.SendMessage(ptrWnd, NativeMethods.WM_COPYDATA, IntPtr.Zero, ptrCopyData);
}
catch (Exception ex)
{
MessageBox.Show(ex.ToString(), "SendMessage Demo", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
finally
{
// Free the allocated memory after the contol has been returned
if (ptrCopyData != IntPtr.Zero)
{
Marshal.FreeCoTaskMem(ptrCopyData);
}
singleMutex.ReleaseMutex();
}
}
}
}