I'm working with TreeView Control in Windows Forms in C#.
Since actual population part of TreeView Control takes a lot of time it freezes the UI. So I'm attempting to do the population using PostMessage Win32 API from a background thread but I found that the Treeview isn't getting inserted with Items.
So I moved the code from background thread to main thread. But then also the Insert Item Code is not working. I got similar code working with TreeView in C++ and trying to do the same thing with C# using interop routines.
I'm not going the usual C# way of treeView1.Nodes.Add("...") because it freezes the UI even if I follow the Delegate method and BackgroundWorker method for populating UI controls from another thread. I'm giving the code I use below. Can some one please help to find the issue with the code.
Also Please note for the TreeView Control I'm using my own simple class derived from TreeView class, where I have overriden the WndProc method to verify the flow of Windows Messages and I can see the messages(TVM_INSERTITEM) are actually getting through but still the item is not getting populated
Also I have got similar interop code working fine from Background Thread for ListView Control but my attempts with TreeView haven't succeeded so far.
Form Class Code
using System;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;
namespace UpdateTreeViewFromAnotherThread
{
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
public struct TVITEM
{
public uint mask;
public IntPtr hItem;
public uint state;
public uint stateMask;
public IntPtr pszText;
public int cchTextMax;
public int iImage;
public int iSelectedImage;
public int cChildren;
public uint lParam;
}
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
public struct TVINSERTSTRUCT
{
public IntPtr hParent;
public IntPtr hInsertAfter;
public TVITEM item;
}
public enum TreeViewInsert
{
TVI_ROOT = -0x10000,
}
[Flags]
public enum TreeViewItemMask
{
TVIF_TEXT = 0x0001,
}
public partial class Form1 : Form
{
const int TV_FIRST = 0x1100;
IntPtr tvInsItemPtr;
TVINSERTSTRUCT tvins;
IntPtr handleTreeView;
[return: MarshalAs(UnmanagedType.Bool)]
[DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)]
static extern bool PostMessage(IntPtr hWnd, uint Msg, IntPtr wParam, IntPtr lParam);
[DllImport("user32.dll", CharSet = CharSet.Auto)]
public static extern IntPtr SendMessage(IntPtr hWnd, int Msg, int wParam, IntPtr lParam);
public enum TreeViewMessage
{
TVM_INSERTITEM = TV_FIRST + 50,
}
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
handleTreeView = treeView1.Handle;
//treeView1.Nodes.Add("hello");
PopulateTree(handleTreeView);
}
public void PopulateTree(IntPtr handle)
{
tvins = new TVINSERTSTRUCT();
tvins.item.mask = (uint)TreeViewItemMask.TVIF_TEXT;
// Set the text of the item.
string productName = "Product";
string value = productName;
byte[] buffer = new byte[100];
buffer = Encoding.Unicode.GetBytes(value + "\0");
tvins.item.pszText = Marshal.AllocHGlobal(buffer.Length);
Marshal.Copy(buffer, 0, tvins.item.pszText, buffer.Length);
tvins.hParent = IntPtr.Zero;
tvins.hInsertAfter = (IntPtr)(TreeViewInsert.TVI_ROOT);
tvInsItemPtr = Marshal.AllocHGlobal(Marshal.SizeOf(tvins));
Marshal.StructureToPtr(tvins, tvInsItemPtr, true);
PostMessage(treeView1.Handle, (uint)TreeViewMessage.TVM_INSERTITEM, IntPtr.Zero, tvInsItemPtr);
//SendMessage(treeView1.Handle, (int)TreeViewMessage.TVM_INSERTITEM, 0, tvInsItemPtr);
}
}
}
MyTreeView Class Code
using System.Windows.Forms;
using System.Runtime.InteropServices;
namespace UpdateTreeViewFromAnotherThread
{
class MyTreeView:TreeView
{
protected override void WndProc(ref Message m)
{
if (m.Msg == 0x1132)
{
TVINSERTSTRUCT anotherTVInsertStruct;
anotherTVInsertStruct = (TVINSERTSTRUCT)Marshal.PtrToStructure(m.LParam, typeof(TVINSERTSTRUCT));
string anotherNodeText = Marshal.PtrToStringAnsi(anotherTVInsertStruct.item.pszText);
}
if(m.Msg == 0x113F)
{
TVITEM anotherTVItem;
anotherTVItem = (TVITEM)Marshal.PtrToStructure(m.LParam, typeof(TVITEM));
string anotherNodeText = Marshal.PtrToStringAnsi(anotherTVItem.pszText);
}
base.WndProc(ref m);
//Trace.WriteLine(m.Msg.ToString() + ", " + m.ToString());
}
}
}
Update_1
Prevented NM_CUSTOMDRAW for Treeview using the below code. Thanks to the code atlink.
protected override void WndProc(ref Message m)
{
switch (m.Msg)
{
case WM_REFLECT + WM_NOTIFY:
{
NMHDR nmhdr = (NMHDR)m.GetLParam(typeof(NMHDR));
switch ((int)nmhdr.code)
{
case NM_CUSTOMDRAW:
NMTVCUSTOMDRAW nmTvDraw = (NMTVCUSTOMDRAW)m.GetLParam(typeof(NMTVCUSTOMDRAW));
switch (nmTvDraw.nmcd.dwDrawStage)
{
case CDDS_ITEMPREPAINT:
m.Result = (IntPtr)CDRF_DODEFAULT;
break;
}
Marshal.StructureToPtr(nmTvDraw, m.LParam, false);
return;
}
break;
}
}
base.WndProc(ref m);
}
So Now If I change my earlier PopulateTree function (note Thread.Sleep()) and its invocation to a background thread as below it will not freeze the UI during the population process
private void button1_Click(object sender, EventArgs e)
{
handleTreeView = treeView1.Handle;
Thread backgroundThread = new Thread(() => PopulateTree(handleTreeView));
backgroundThread.Start();
}
public void PopulateTree(IntPtr handle)
{
for(int i =0; i< 1000; i++)
{
tvins = new TVINSERTSTRUCT();
tvins.item.mask = (uint)TreeViewItemMask.TVIF_TEXT;
// Set the text of the item.
string productName = "Product_" + i.ToString();
string value = productName;
byte[] buffer = new byte[100];
buffer = Encoding.Unicode.GetBytes(value + "\0");
tvins.item.pszText = Marshal.AllocHGlobal(buffer.Length);
Marshal.Copy(buffer, 0, tvins.item.pszText, buffer.Length);
tvins.hParent = IntPtr.Zero;
tvins.hInsertAfter = (IntPtr)(TreeViewInsert.TVI_ROOT);
tvInsItemPtr = Marshal.AllocHGlobal(Marshal.SizeOf(tvins));
Marshal.StructureToPtr(tvins, tvInsItemPtr, true);
PostMessage(handle, (uint)TreeViewMessage.TVM_INSERTITEM, IntPtr.Zero, tvInsItemPtr);
Thread.Sleep(1000);
}
}
