将FolderBrowserDialog搬进“下拉列表框”中！
前几天见有人问如何在ComboBox中加入复选框的问题，从那时起我就想在里面加点复杂点但有使用价值的东西，思来想去我决定将FolderBrowserDialog塞进去，因为我对系统提供的那个一直觉得有点麻烦！标题中之所以在下拉列表框加引号，是说它不是在ComboBox控件的基础上扩展，不是从Control扩展，只不过是外观类似ComboBox而已，所以该控件只能从下拉部分选择目录而不支持手动输入，当然了，因为那个标准的FBD（FolderBrowserDialog，下同）支持新建目录功能，所以这个自定义控件也支持新建，另外还可以将选定的目录在资源管理器中打开，本来我还打算加上对文件夹重命名的，但放弃了！咱这虽然有点山寨，但该有的还是不能缺！
效果就是下面两幅图片所示：
以下是步骤代码节选：
- 首先需要三个控件，一个是UserControl或Control，它负责会制ComboBox外观和绘制数据，另一个是TreeView，它负责显示本机的文件系统目录，但不能直接用，需要修理修理。最后一个就是负责承载TreeView的ToolStripDropDown，它就是平时不可见的下拉的那部分！、
- 添加引用(COM)：Shell32.dll;
- 对TreeView的修改：
//定义一个对象，负责加载目录.
Shell32.ShellClass shell = new Shell32.ShellClass();
// 获取或设置控件选择的路径
public string SelectedPath{get;set;}
//获取或设置控件使用的根目录。
public Environment.SpecialFolder Root{get;set;}
//隐藏Nodes属性，这步并非可有可无，是必须！
[Browsable(false)]
[EditorBrowsable( EditorBrowsableState.Never)]
[Localizable(false)]
[DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
public new TreeNodeCollection Nodes
{
get { return base.Nodes; }
}
//然后设置以下属性
ShowNodeToolTips = true;
ShowRootLines = false;
BeforeExpand += new TreeViewCancelEventHandler(EtFolderTreeView_BeforeExpand);
//使控件自绘制，
DrawMode = TreeViewDrawMode.OwnerDrawAll;
ImageList = new ImageList();//设置该属性但不向里面添加任何图片，目换是让TreeView在每个节点处留出绘制图标的位置。
DrawNode += new DrawTreeNodeEventHandler(FolderTreeView_DrawNode);
AfterSelect += new TreeViewEventHandler(EtFolderTreeView_AfterSelect);
FillNodesFor(null);//null参数表示当前添加的为要节点，但不限于Desktop，取决于Root属性的设置。
}
。。。。。。
//在当前选定节点下新建目录
public bool NewFolderInSelectedFolder(string name){}
//刷新指定节点，即重新加载其下子目录，然后使其展开
public void RefreshItem(TreeNode node)
{
FillNodesFor(node);
if (!node.IsExpanded) node.Expand();
}
// 在每次选中节点后检查其对应的是快捷方式还是目录，验证目录或快捷方式的目标位置的可用性并设置SelectedPath属性。
void EtFolderTreeView_AfterSelect(object sender, TreeViewEventArgs e)
{
PathEntry pe = (PathEntry)e.Node.Tag;
string path = pe.IsLink ? pe.LinkTarget : pe.Path;
if (Directory.Exists(path))
SelectedPath = path;
else
SelectedPath = "";
}
//为提高性能，设定在某节点展开前加载其对应目录的子目录
void EtFolderTreeView_BeforeExpand(object sender, TreeViewCancelEventArgs e)
{
FillNodesFor(e.Node);
}
void FolderTreeView_DrawNode(object sender, DrawTreeNodeEventArgs e)
{
if (!e.Node.IsVisible) return;
Rectangle rect = new Rectangle(e.Bounds.Location, new Size(16, 16));
int indent = this.Indent * e.Node.Level;
if (CheckBoxes) indent += this.Indent;
rect.Offset(indent + 1, 1);
Icon icon = null;
try
{
PathEntry pe = (PathEntry)e.Node.Tag;
if (pe.vDir.ToString() == "0") icon = PlatFormInformation.ThemesIcons.GetDesktopIcon(true);
if (icon == null)
{
//比用Path好，自动区分需要特殊处理的图标，与桌面上的我的文档和与其对应的物理目录
// 不应用同一图标。而当pe为指向某文件夹的快捷方式时，使用Path为的是显示箭头
string path =pe.IsLink?pe.Path: pe.vDir.ToString();
if (path != null)
{
Win32.Shell32Api.SHFILEINFO info = new Etonesoft.Win32.Shell32Api.SHFILEINFO();
Win32.Shell32Api.SHFILEINFOITEM item = Win32.Shell32Api.SHFILEINFOITEM.SHGFI_ICON | Etonesoft.Win32.Shell32Api.SHFILEINFOITEM.SHGFI_SMALLICON | Etonesoft.Win32.Shell32Api.SHFILEINFOITEM.SHGFI_ATTRIBUTES;
if (e.Node.IsExpanded) item |= Etonesoft.Win32.Shell32Api.SHFILEINFOITEM.SHGFI_OPENICON;
Win32.Shell32Api.SHGetFileInfo(path, Etonesoft.Win32.Shell32Api.SHFILEATTRIBUTE.FILE_ATTRIBUTE_DIRECTORY, ref info, item);
// 之所以进行如下代码的替换，是因为个别节点，如网上邻居下的整个网络，无法从其自身的Path属性获取图标，
//需要与其父节点的Path属性相结合，尽管如此，依然无法获取整个网络节点的各子节点图标，以后需改进！！
//if (info.hIcon != IntPtr.Zero) icon = Icon.FromHandle(info.hIcon);
TreeNode tn = e.Node;
while (info.hIcon==IntPtr.Zero && tn.Parent!=null)
{
path = ((PathEntry)e.Node.Parent.Tag).vDir + "//"+path;
Win32.Shell32Api.SHGetFileInfo(path, Etonesoft.Win32.Shell32Api.SHFILEATTRIBUTE.FILE_ATTRIBUTE_DIRECTORY, ref info, item);
tn = tn.Parent;
}
if (info.hIcon != IntPtr.Zero) icon = Icon.FromHandle(info.hIcon);
}
}
if (icon != null)
{
e.Graphics.DrawIcon(icon, rect);
icon.Dispose();
}
}
catch (InvalidCastException)
{ return; }
catch (NullReferenceException)
{
if (e.Node.Tag == null) return;
throw;
}
catch { throw; }
finally { e.DrawDefault = true; }
}
protected override void OnNodeMouseClick(TreeNodeMouseClickEventArgs e)
{
base.OnNodeMouseClick(e);
//注释：下句不可缺少，否则，如果之前该节点的某一子节点已处于
// 选中状态，则该节点不会因此次鼠标点击事件而引发AfterSelected事件。
this.SelectedNode = e.Node;
if(e.Node.Bounds.Contains(e.Location))e.Node.Toggle();
}
private void FillNodesFor(TreeNode treeNode)
{
try
{
PathEntry peRoot;
IEnumerable<TreeNode> nodes;
this.Cursor = Cursors.WaitCursor;
if (treeNode == null)
{//加载根目录
this.Nodes.Clear();
object vDir = Environment.GetFolderPath(Root);
switch (Root)
{
case Environment.SpecialFolder.MyComputer:
vDir = "::" + PlatFormInformation.CLSIDs.MyComputer;
break;
case Environment.SpecialFolder.MyDocuments:
vDir = "::" + PlatFormInformation.CLSIDs.MyDocuments;
break;
case Environment.SpecialFolder.Desktop://此处比较特殊，要想加载桌面，参数必须为0，而不是其物理目录。只有这样才会出现我的文档，我的电脑回收站及网上邻居等
vDir = 0;
break;
default:
break;
}
peRoot = GetPathEntry(null, (shell.NameSpace(vDir) as Shell32.Folder3).Self);
this.Nodes.Add(treeNode = GetTreeNodeFromFileItem(peRoot));
}
else
{
treeNode.Nodes.Clear();
peRoot = (PathEntry)treeNode.Tag;
// 拒绝回收站里被逻辑删除的文件，通过检查对目录里是否以回收站的CLSID确定。
if (peRoot.vDir.ToString().EndsWith(PlatFormInformation.CLSIDs.RecycleBin)) return;
}
Shell32.Folder folder = shell.NameSpace(peRoot.vDir);
if (folder == null) return;
nodes = from Shell32.FolderItem dir in folder.Items()
let pe = GetPathEntry(treeNode, dir)
where pe.Valid
select GetTreeNodeFromFileItem(pe);
treeNode.Nodes.AddRange(nodes.Where(x => (x != null)).ToArray());
}
catch (FileNotFoundException)
{
treeNode.Remove();
return;
}
catch (UnauthorizedAccessException){ return; }
catch(NotImplementedException){ return; }
catch (Exception ex)
{
MessageBox.Show(ex.ToString() + "/n" + treeNode.Name);
return;
}
finally { this.Cursor = Cursors.Default; }
}
//经过该判断，过滤出来的文件夹项只能是文件夹或快捷方式
private PathEntry GetPathEntry(TreeNode treeNode, Shell32.FolderItem x)
{
PathEntry entry = new PathEntry();
entry.vDir = entry.Path = x.Path;
entry.Title = x.Name;
Environment.SpecialFolder sf;
if (GetSpecialFolder(x.Path,out sf))
{
entry.IsSpecialFolder = true;
entry.SpecialFolder = sf;
if (treeNode==null || treeNode.Level ==0)
{
switch (sf)
{
case Environment.SpecialFolder.Desktop:
entry.vDir =0;
break;
case Environment.SpecialFolder.MyComputer:
entry.vDir = "::" + PlatFormInformation.CLSIDs.MyComputer;
break;
case Environment.SpecialFolder.MyDocuments:
entry.vDir = "::" + PlatFormInformation.CLSIDs.MyDocuments;
break;
default:
break;
}
}
}
try
{
entry.Local = true;
if (x.IsFolder)
{
entry.Valid= treeNode==null || !treeNode.Nodes.ContainsKey(x.Path);
//如果不作判断，则桌面上的“我的文档”的图标将被绘制为变通的文件夹！
if (x.Name == "我的文档")//该处判断不够合理，需要改进！！
{
entry.IsSpecialFolder = true;
entry.SpecialFolder= Environment.SpecialFolder.MyDocuments;
}
}
if (x.IsLink)
{
Shell32.ShellLinkObject link = x.GetLink as Shell32.ShellLinkObject;
if (link != null && File.Exists(x.Path) && Directory.Exists(link.Path))// &&
//上述条件最后两项之所以分别用Directory和File进行测试是针对快捷方式的特点，用File是测试快捷方式
//文件本身测试，这可以快捷方式文件本身的位置；用Directory是测试快捷方式所指向的目标文件夹
//是否对本机可见及目标位置是否是一个文件夹而不是一个文件，可避免目标位置无效的快捷方式出现在列表中。
{
entry.Valid= treeNode==null || !treeNode.Nodes.ContainsKey(link.Path);
entry.IsLink = true;
entry.vDir = entry.LinkTarget = link.Path;
}
}
return entry;
}
catch (FileNotFoundException) { return entry; }
catch { throw; }
}
//根据指定的路径确定当前是否是一个特殊文件夹，即Environment。SpecialFolder
//但这个地方我认为判定手段有点问题，但又想不到更好的
private bool GetSpecialFolder(string p, out Environment.SpecialFolder sf)
{
switch (p)
{
case "::" + PlatFormInformation.CLSIDs.MyComputer:
sf = Environment.SpecialFolder.MyComputer;
return true;
case "::" + PlatFormInformation.CLSIDs.MyDocuments:
sf = Environment.SpecialFolder.MyDocuments;
return true;
default:
Array array = Enum.GetValues(typeof(Environment.SpecialFolder));
foreach (Environment.SpecialFolder item in array)
{
if (p==Environment.GetFolderPath(item))
{
sf = item;
return true;
}
}
sf = Environment.SpecialFolder.Desktop;
return false;
}
}
//根据取得的PathEntry构造TreeNode,但每个新建的节点都要加一个空节点，目录嘛，就是让其首次出现时也会在左侧出现加号，只有这样才会有机会触发AfterExpend事件进而加载其下的子目录，虽然有 //的目录根本没有子目录
private TreeNode GetTreeNodeFromFileItem(PathEntry pe)
{
TreeNode node= new TreeNode { Text = pe.Title, Tag = pe };
node.Nodes.Add("");
return node;
}
//一个结构，包含构造树节点的必需信息
struct PathEntry
{
internal bool Valid;
internal bool IsSpecialFolder;
internal bool Local;
internal bool IsLink;
internal string LinkTarget;
internal object vDir;
internal string Title;
internal string Path;
internal Environment.SpecialFolder SpecialFolder;
}
//实现将选中的目录在系统Explorer中打开
internal void OpenFolder()
{ }
。。。。。。
4. 对UserControl的扩展
//EtComboBoxHost是从UserControl继承而来的，它里面定义了一个ToolStripDropDown的东西（本例中名称为controlDropDown）。只在放在里面的东西才会出现在下拉部分中，
//并且，还实现在弹出和隐藏的方法。
public partial class EtFolderSelector : EtComboBoxHost
{
//左侧的图像栏的宽度，因为有个TreeView在上面，想会制OFFICE2007中的效果，否则的话，如果里面只ToolStripMenuItem什么的，完全可以将controlDropDown改成ToolStripDropDownMenu
//，它可以实现左侧的边栏，现在我不想让TreeView也有边栏，只能扩展ToolStripDropDown以实现边栏了。
private const int IMAGEMARGIN = 26;
private EtFolderTreeView treeView = new EtFolderTreeView();
private ToolStripTextBox tstbxNewFolder = new ToolStripTextBox();
private ToolStripMenuItem tsmiSelectPath = new ToolStripMenuItem("选择文件夹");
ToolStripMenuItem tsmiOpenInExplorer = new ToolStripMenuItem("打开文件夹");
#region RootDirectory 属性定义
private event EventHandler e_RootDirectoryChanged;
/// <summary>
/// 当RootDirectory属性更改时发生。
/// </summary>
public event EventHandler RootDirectoryChanged
{
add { e_RootDirectoryChanged += value; }
remove { e_RootDirectoryChanged -= value; }
}
/// <summary>
/// 引发按控件的RootDirectory属性。
/// </summary>
/// <param name="e">包含事件所需要数据的事件参数对象。</param>
protected virtual void OnRootDirectoryChanged(EventArgs e)
{
if(this.ControlDropDown.Visible)this.HideDropDown();
treeView.Root = m_RootDirectory;
SelectedPath = Environment.GetFolderPath(m_RootDirectory);
//如果控件的RootDirectoryChanged事件不为空且委托链长度大于0，则引发该事件。
if (e_RootDirectoryChanged != null && e_RootDirectoryChanged.GetInvocationList().Length > 0)
{
e_RootDirectoryChanged(this, e);
}
}
private Environment.SpecialFolder m_RootDirectory = Environment.SpecialFolder.Desktop;
/// <summary>
/// 获取或设置控件的初始目录。
/// </summary>
[Category("扩展")]
[Browsable(true)]
[DefaultValue(typeof(Environment.SpecialFolder), "Desktop")]
[Description("获取或设置控件的初始目录。")]
public Environment.SpecialFolder RootDirectory
{
get
{
return m_RootDirectory;
}
set
{
if (m_RootDirectory == value) return;
m_RootDirectory = value;
OnRootDirectoryChanged(new EventArgs());
}
}
#endregion
#region SelectedPath 属性定义
public string SelectedPath{get;set;}
#endregion
public EtFolderSelector()
: base()
{
InitializeComponent();
base.RenderMode = ToolStripRenderMode.ManagerRenderMode;
treeView.BorderStyle = BorderStyle.None;
treeView.AfterSelect += new TreeViewEventHandler(treeView_AfterSelect);
treeView.HideSelection = false;
treeView.MinimumSize = new Size(200, 0);
tsmiSelectPath.Click += new EventHandler(tsmiSelectPath_Click);
tsmiOpenInExplorer.Click += new EventHandler(tsmiOpenInExpore_Click);
tsmiOpenInExplorer.Tag = "OPEN";
tstbxNewFolder.Tag = "NEW";
tsmiSelectPath.Tag = "SELECT";
tsmiSelectPath.TextAlign = ContentAlignment.MiddleLeft;
tsmiOpenInExplorer.TextAlign= ContentAlignment.MiddleLeft;
tstbxNewFolder.ToolTipText = "[新建文件夹]，要新建文件夹，请输入新文件夹名称后按回车";
tstbxNewFolder.KeyDown += new KeyEventHandler(tstbxNewFolder_KeyDown);
InitControlDropDown();
}
......
protected override void OnDropDownOpening(CancelEventArgs e)
{
base.OnDropDownOpening(e);
//设置下拉部分的最小尺寸
foreach (ToolStripItem item in ControlDropDown.Items)
{
ToolStripControlHost host = (item as ToolStripControlHost);
if (host != null)
host.Control.MinimumSize = new Size(this.Width - 2 * (IMAGEMARGIN + 2),host.Control==treeView?200:0);
}
}
protected override void OnDropDownClosed(EventArgs e)
{
base.OnDropDownClosed(e);
tstbxNewFolder.Text = "";
}
private void InitControlDropDown()
{
//PlatFormInformation.ShellStockIcons，在其他地方定义的类型，负责访问Shell32.dll里的图标，参数TRUE表示获取小图标，否则为大图标
ControlDropDown.ImageList = new ImageList { ColorDepth= ColorDepth.Depth32Bit};
ControlDropDown.ImageList.Images.Add("OPEN", PlatFormInformation.ShellStockIcons.GetFolderOpenned(true));
ControlDropDown.ImageList.Images.Add("NEW", PlatFormInformation.ShellStockIcons.GetNewFolder(true));
ControlDropDown.ImageList.Images.Add("SELECT", PlatFormInformation.ShellStockIcons.GetIconFor(110,true));
ControlDropDown.LayoutStyle = ToolStripLayoutStyle.VerticalStackWithOverflow;
ControlDropDown.Items.Add(new ToolStripControlHost(treeView));
ControlDropDown.Items.Add(new ToolStripSeparator());
ControlDropDown.Items.Add(tstbxNewFolder);
ControlDropDown.Items.Add(tsmiOpenInExplorer);
ControlDropDown.Items.Add(tsmiSelectPath);
ControlDropDown.Paint += new PaintEventHandler(ControlDropDown_Paint);
//为配合边栏，设置各项（除TreeView外）的Margin，让出左侧一定的宽度。
foreach (ToolStripItem item in ControlDropDown.Items)
{
if (item is ToolStripControlHost)
{
if ((item as ToolStripControlHost).Control == treeView)
continue;
else if (item is ToolStripTextBox)
{
item.Margin = new Padding(IMAGEMARGIN + 4,1, IMAGEMARGIN , 1);
continue;
}
}
item.Margin = new Padding(IMAGEMARGIN +2,1,2,1);
item.Padding = new Padding(1, 3, 1, 3);
}
}
void ControlDropDown_Paint(object sender, PaintEventArgs e)
{
//绘制左侧边栏
ControlDropDown.Renderer.DrawImageMargin(
new ToolStripRenderEventArgs(
e.Graphics,
ControlDropDown,
ControlDropDown.DisplayRectangle.LeftPart(IMAGEMARGIN),
SystemColors.Menu)
);
//绘制各项的图标，如果有。
foreach (ToolStripItem item in ControlDropDown.Items)
{
Rectangle rect = item.Bounds.LeftPart(IMAGEMARGIN);
rect.X = 0;
rect.Inflate((16-rect.Width) / 2, (16-rect.Height) / 2);
Image img = null;
if(item.Tag!=null)img=ControlDropDown.ImageList.Images[item.Tag.ToString()];
ControlDropDown.Renderer.DrawItemImage(new ToolStripItemImageRenderEventArgs(e.Graphics,item,img,rect));
}
}
//将用户选中的目录绘制到用户的客户区（ContentRect，在父类中定义！）
protected override void OnPaint(PaintEventArgs e)
{
base.OnPaint(e);
e.Graphics.DrawString(this.SelectedPath, this.Font, this.Focused ? SystemBrushes.HighlightText : SystemBrushes.ControlText, this.ContentRect, new StringFormat { Alignment = StringAlignment.Near, LineAlignment = StringAlignment.Near, Trimming = StringTrimming.EllipsisPath, FormatFlags = StringFormatFlags.NoClip | StringFormatFlags.NoWrap });
}
需要说明的是里面有几个东西是我在另的地方定义的，如PlatformImformation等。
