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using System;
using System.ComponentModel;
using System.Windows.Forms;

namespace CustomTreeViewLabelEdit
{
  internal class TreeViewEx : TreeView
  {
    // Extending the LabelEdit functionality of a TreeView to include validation
    // http://cyotek.com/blog/extending-the-labeledit-functionality-of-a-treeview-to-include-validation

    #region Instance Fields

    private string _postEditText;

    #endregion

    #region Events

    [Category("Behavior")]
    public event EventHandler<NodeRequestTextEventArgs> RequestDisplayText;

    [Category("Behavior")]
    public event EventHandler<NodeRequestTextEventArgs> RequestEditText;

    [Category("Behavior")]
    public event EventHandler<NodeLabelEditEventArgs> ValidateLabelEdit;

    #endregion

    #region Overridden Members

    protected override void OnAfterLabelEdit(NodeLabelEditEventArgs e)
    {
      if (e.Label != null) // if the user cancelled the edit this event is still raised, just with a null label
      {
        NodeLabelEditEventArgs validateEventArgs;

        e.CancelEdit = true; // cancel the built in operation so we can substitute our own

        validateEventArgs = new NodeLabelEditEventArgs(e.Node, e.Label);

        this.OnValidateLabelEdit(validateEventArgs); // validate the users input

        if (validateEventArgs.CancelEdit)
        {
          // if the users input was invalid, enter edit mode again using the previously entered text to give them the chance to correct it
          _postEditText = e.Label;
          e.Node.BeginEdit();
        }
        else
        {
          // otherwise, continue with the edit
          NodeRequestTextEventArgs displayTextArgs;

          displayTextArgs = new NodeRequestTextEventArgs(e.Node, e.Label);
          this.OnRequestDisplayText(displayTextArgs);

          if (!displayTextArgs.Cancel)
            e.Node.Text = displayTextArgs.Label;
        }
      }

      base.OnAfterLabelEdit(e);
    }

    protected override void OnBeforeLabelEdit(NodeLabelEditEventArgs e)
    {
      NodeRequestTextEventArgs editTextArgs;

      // get the text to apply to the label
      editTextArgs = new NodeRequestTextEventArgs(e.Node, _postEditText ?? e.Node.Text);
      if (_postEditText == null)
        this.OnRequestEditText(editTextArgs);
      _postEditText = null;

      // cancel the edit if required
      if (editTextArgs.Cancel)
        e.CancelEdit = true;

      // apply the text to the EDIT control
      if (!e.CancelEdit)
      {
        IntPtr editHandle;

        editHandle = NativeMethods.SendMessage(this.Handle, NativeMethods.TVM_GETEDITCONTROL, IntPtr.Zero, IntPtr.Zero); // Get the handle of the EDIT control
        if (editHandle != IntPtr.Zero)
          NativeMethods.SendMessage(editHandle, NativeMethods.WM_SETTEXT, IntPtr.Zero, editTextArgs.Label); // And apply the text. Simples.
      }

      base.OnBeforeLabelEdit(e);
    }

    #endregion

    #region Members

    protected virtual void OnRequestDisplayText(NodeRequestTextEventArgs e)
    {
      EventHandler<NodeRequestTextEventArgs> handler;

      handler = this.RequestDisplayText;

      if (handler != null)
        handler(this, e);
    }

    protected virtual void OnRequestEditText(NodeRequestTextEventArgs e)
    {
      EventHandler<NodeRequestTextEventArgs> handler;

      handler = this.RequestEditText;

      if (handler != null)
        handler(this, e);
    }

    protected virtual void OnValidateLabelEdit(NodeLabelEditEventArgs e)
    {
      EventHandler<NodeLabelEditEventArgs> handler;

      handler = this.ValidateLabelEdit;

      if (handler != null)
        handler(this, e);
    }

    #endregion
  }
}