最近做Winform项目需要用到类似ComboBox的TreeView控件。
虽然各种第三方控件很多，但是存在各种版本不兼容问题。所以自己写了个简单的ComboTreeView控件。
下图是实现效果：
目前实现的比较简单，能满足我项目中的需求。
此处是项目中的代码简化后的版本，供大家参考。
using System;
using System.Collections.Generic;
using System.Windows.Forms; namespace CustomControl.Tree
{
public abstract class ComboTreeView<T> : ComboBox where T : class
{
protected const int WM_LBUTTONDOWN = 0x0201, WM_LBUTTONDBLCLK = 0x0203; protected TreeView treeView;
protected ToolStripControlHost treeViewHost;
protected ToolStripDropDown dropDown;
protected bool dropDownOpen = false;
protected TreeNode selectedNode;
protected T toBeSelected; public ComboTreeView(TreeView internalTreeView)
{
if (null == internalTreeView)
{
throw new ArgumentNullException("internalTreeView");
}
this.InitializeControls(internalTreeView);
} public event TreeNodeChangedEventHandler TreeNodeChanged; protected virtual void InitializeControls(TreeView internalTreeView)
{
this.treeView = internalTreeView;
this.treeView.BorderStyle = BorderStyle.FixedSingle;
this.treeView.Margin = new Padding();
this.treeView.Padding = new Padding();
this.treeView.AfterExpand += new TreeViewEventHandler(this.WhenAfterExpand); this.treeViewHost = new ToolStripControlHost(this.treeView);
this.treeViewHost.Margin = new Padding();
this.treeViewHost.Padding = new Padding();
this.treeViewHost.AutoSize = false; this.dropDown = new ToolStripDropDown();
this.dropDown.Margin = new Padding();
this.dropDown.Padding = new Padding();
this.dropDown.AutoSize = false;
this.dropDown.DropShadowEnabled = true;
this.dropDown.Items.Add(this.treeViewHost);
this.dropDown.Closed += new ToolStripDropDownClosedEventHandler(this.OnDropDownClosed); this.DropDownWidth = this.Width;
base.DropDownStyle = ComboBoxStyle.DropDownList;
base.SizeChanged += new EventHandler(this.WhenComboboxSizeChanged);
} public new ComboBoxStyle DropDownStyle
{
get { return base.DropDownStyle; }
set { base.DropDownStyle = ComboBoxStyle.DropDownList; }
} public virtual TreeNode SelectedNode
{
get { return this.selectedNode; }
private set { this.treeView.SelectedNode = value; }
} public virtual T SelectedNodeData
{
get { return (T)base.SelectedItem; }
set
{
this.toBeSelected = value;
this.UpdateComboBox(value);
}
} protected new int SelectedIndex
{
get { return base.SelectedIndex; }
set { base.SelectedIndex = value; }
} protected new object SelectedItem
{
get { return base.SelectedItem; }
set { base.SelectedItem = value; }
} public virtual string DisplayMember { get; set; } = "Name"; /// <summary>Gets the internal TreeView control.</summary>
public virtual TreeView TreeView => this.treeView; /// <summary>Gets the collection of tree nodes that are assigned to the tree view control.</summary>
/// <returns>A <see cref="T:System.Windows.Forms.TreeNodeCollection" /> that represents the tree nodes assigned to the tree view control.</returns>
public virtual TreeNodeCollection Nodes => this.treeView.Nodes; public new int DropDownHeight { get; set; } = ; public new int DropDownWidth { get; set; } = ; protected virtual void ShowDropDown()
{
this.dropDown.Width = this.Width;
this.dropDown.Height = this.DropDownHeight;
this.treeViewHost.Width = this.Width;
this.treeViewHost.Height = this.DropDownHeight;
this.treeView.Font = this.Font;
this.dropDown.Focus();
this.dropDownOpen = true;
this.dropDown.Show(this, , base.Height);
} protected virtual void HideDropDown()
{
this.dropDown.Hide();
this.dropDownOpen = false;
} protected virtual void ToggleDropDown()
{
if (!this.dropDownOpen)
{
this.ShowDropDown();
}
else
{
this.HideDropDown();
}
} protected override void WndProc(ref Message m)
{
if ((WM_LBUTTONDOWN == m.Msg) || (WM_LBUTTONDBLCLK == m.Msg))
{
if (!this.Focused)
{
this.Focus();
}
this.ToggleDropDown();
}
else
{
base.WndProc(ref m);
}
} protected override void Dispose(bool disposing)
{
if (disposing)
{
if (this.dropDown != null)
{
this.dropDown.Dispose();
this.dropDown = null;
}
}
base.Dispose(disposing);
} protected virtual void WhenTreeNodeChanged(TreeNode newValue)
{
if ((null != this.selectedNode) || (null != newValue))
{
bool changed;
if ((null != this.selectedNode) && (null != newValue))
{
changed = (this.selectedNode.GetHashCode() != newValue.GetHashCode());
}
else
{
changed = true;
} if (changed)
{
if (null != this.TreeNodeChanged)
{
try
{
this.TreeNodeChanged.Invoke(this, new TreeNodeChangedEventArgs(this.selectedNode, newValue));
}
catch (Exception)
{
// do nothing
}
} this.selectedNode = newValue;
this.UpdateComboBox(this.GetTreeNodeData(newValue));
}
}
} protected virtual void OnDropDownClosed(object sender, ToolStripDropDownClosedEventArgs e)
{
if (null == this.toBeSelected)
{
var selectedNode = this.treeView.SelectedNode;
this.WhenTreeNodeChanged(selectedNode);
}
} protected virtual void UpdateComboBox(T data)
{
base.DisplayMember = this.DisplayMember; // update DisplayMember
if (null != data)
{
this.DataSource = new List<T>() { data };
this.SelectedIndex = ;
}
else
{
this.DataSource = null;
}
} protected virtual void WhenAfterExpand(object sender, TreeViewEventArgs e)
{
if (null != this.toBeSelected)
{
if (this.SelectChildNode(e.Node.Nodes, this.toBeSelected))
{
this.toBeSelected = null;
}
}
} protected virtual void WhenComboboxSizeChanged(object sender, EventArgs e)
{
this.DropDownWidth = base.Width;
} public virtual bool SelectChildNode(TreeNodeCollection nodes, T data)
{
var node = this.FindChildNode(nodes, data);
if (null != node)
{
this.DoSelectTreeNode(node);
return true;
}
else
{
return false;
}
} protected abstract bool Identical(T x, T y); protected virtual void DoSelectTreeNode(TreeNode node)
{
this.SelectedNode = node;
this.ExpandTreeNode(node.Parent);
} public virtual TreeNode FindChildNode(TreeNodeCollection nodes, T data)
{
foreach (TreeNode node in nodes)
{
var nodeData = this.GetTreeNodeData(node);
if (this.Identical(nodeData, data))
{
return node;
}
} return null;
} public virtual void ExpandTreeNode(TreeNode node)
{
if (null != node)
{
node.Expand();
this.ExpandTreeNode(node.Parent);
}
} public abstract T GetTreeNodeData(TreeNode node);
}
}