C#

public class Form1
{
    Form2 myForm2;
    Button myButton;
    public Form1()
    {
        myForm2 = new Form2();

        myButton = new Button();
        myButton.Click += new EventHandler(myButton_Click);
    }

    private void myButton_Click(object sender, EventArgs e)
    {
        myForm2.Show();
    }
}

<br />
private void SendBill()<br />
{<br />
            SmtpClient client = new SmtpClient("my.mailserver.net");<br />
            MailAddress toAddr = new MailAddress("anybody@hotmail.com");<br />
            MailAddress fromAddr = new MailAddress("test@mailserver.net");<br />
            MailMessage message = new MailMessage(fromAddr, toAddr);<br />
            message.Subject = "Test Mail";<br />
            message.Body = "This is a test.";<br />
            client.Send(message);<br />
}<br />

<pre><br />
public byte[] ToBytes()<br />
{<br />
   byte[] buff = new byte[Marshal.SizeOf(typeof(MyType))];<br />
   GCHandle handle = GCHandle.Alloc(buff, GCHandleType.Pinned);<br />
   Marshal.StructureToPtr(this, handle.AddrOfPinnedObject(), false);<br />
   handle.Free();<br />
   return buff;<br />
}<br />
</pre><br />
<br />
That code will marshal the struct to a byte[], and from that code, the code for marshaling back to a struct comes easy:<br />
<br />
<code lang=cs><pre><br />
public static MyType FromBytes(byte[] buff)<br />
{<br />
   GCHandle handle = GCHandle.Alloc(buff, GCHandleType.Pinned);<br />
   MyType mt = (MyType)Marshal.PtrToStructure(handle.AddrOfPinnedObject(), typeof(MyType)); // because ptrtostructure returns an object :-\<br />
   handle.Free();<br />
   return mt;<br />
}<br />
</pre><br />
<br />
<br />
Now as for chaining structures together, you can do that yourself using Array.Copy() and copying into a byte[]<br />
<br />
Passing back the data as an IntPtr requires only slight modification to the original functions:<br />
<br />
<code lang=cs><pre><br />
public IntPtr ToIntPtr()<br />
{<br />
   byte[] buff = new byte[Marshal.SizeOf(typeof(MyType))];<br />
   IntPtr handle = Marshal.AllocHGlobal(buff.Length);<br />
   Marshal.StructureToPtr(this, handle, true); // passing false for that last param can cause memory leaks<br />
   return handle;<br />
}<br />
<br />
public static MyType FromIntPtr(IntPtr ptr)<br />
{<br />
   MyType mt = (MyType)Marshal.PtrToStructure(ptr, typeof(MyType)); // because ptrtostructure returns an object :-\<br />
   //Marshal.FreeHGlobal(ptr); - only do this if you know you won't be using that IntPtr again<br />
   return mt;<br />
}<br />

byte[] buf = new byte[1000];
unsafe
{
  fixed (byte* b = buf)
  {
    Header *header = (Header *)b;
    Cmd1SpecificData* specdata = (Cmd1SpecificData *)(header + 1);
    header->cmd = 1;
    header->flags = 999;
    specdata->param1ForCommand1 = 123.456;

    APICALL(b);
  }
}