我有一个包含组合框控件的表单。我已将下拉样式属性选择为 DropDown。我还将下拉宽度设置为 250。我将自动完成模式设置为建议，将自动完成源设置为列表项。当我单击下拉菜单时，它工作得非常好。但是当我输入一些东西时，自动完成模式会激活一个宽度较小的下拉菜单。
任何帮助表示赞赏。我想知道如何通过代码增加自动完成下拉菜单的宽度，以便正确查看列表项。我正在使用 C#。
几个月前我曾问过这个问题，但没有得到正确的答案。现在客户想要它不好:( ??
【问题讨论】：
标签： c# .net winforms visual-studio-2008 combobox
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Runtime.InteropServices;
using System.Text;
using System.Windows.Forms;
/// <summary>
/// Represents an ComboBox with additional properties for setting the
/// size of the AutoComplete Drop-Down window.
/// </summary>
public class ComboBoxEx : ComboBox
{
private int acDropDownHeight = 106;
private int acDropDownWidth = 170;
//<EditorBrowsable(EditorBrowsableState.Always), _
[Browsable(true), Description("The width, in pixels, of the auto complete drop down box"), DefaultValue(170)]
public int AutoCompleteDropDownWidth
{
get { return acDropDownWidth; }
set { acDropDownWidth = value; }
}
//<EditorBrowsable(EditorBrowsableState.Always), _
[Browsable(true), Description("The height, in pixels, of the auto complete drop down box"), DefaultValue(106)]
public int AutoCompleteDropDownHeight
{
get { return acDropDownHeight; }
set { acDropDownHeight = value; }
}
protected override void OnHandleCreated(EventArgs e)
{
base.OnHandleCreated(e);
ACWindow.RegisterOwner(this);
}
#region Nested type: ACWindow
/// <summary>
/// Provides an encapsulation of an Auto complete drop down window
/// handle and window proc.
/// </summary>
private class ACWindow : NativeWindow
{
private static readonly Dictionary<IntPtr, ACWindow> ACWindows;
#region "Win API Declarations"
private const UInt32 WM_WINDOWPOSCHANGED = 0x47;
private const UInt32 WM_NCDESTROY = 0x82;
private const UInt32 SWP_NOSIZE = 0x1;
private const UInt32 SWP_NOMOVE = 0x2;
private const UInt32 SWP_NOZORDER = 0x4;
private const UInt32 SWP_NOREDRAW = 0x8;
private const UInt32 SWP_NOACTIVATE = 0x10;
private const UInt32 GA_ROOT = 2;
private static readonly List<ComboBoxEx> owners;
[DllImport("user32.dll")]
private static extern bool EnumThreadWindows(int dwThreadId, EnumThreadDelegate lpfn, IntPtr lParam);
[DllImport("user32.dll")]
private static extern IntPtr GetAncestor(IntPtr hWnd, UInt32 gaFlags);
[DllImport("kernel32.dll")]
private static extern int GetCurrentThreadId();
[DllImport("user32.dll")]
private static extern void GetClassName(IntPtr hWnd, StringBuilder lpClassName, int nMaxCount);
[DllImport("user32.dll")]
private static extern bool SetWindowPos(IntPtr hWnd, IntPtr hWndInsertAfter, int X, int Y, int cx, int cy,
uint uFlags);
[DllImport("user32.dll")]
private static extern bool GetWindowRect(IntPtr hWnd, ref RECT lpRect);
#region Nested type: EnumThreadDelegate
private delegate bool EnumThreadDelegate(IntPtr hWnd, IntPtr lParam);
#endregion
#region Nested type: RECT
[StructLayout(LayoutKind.Sequential)]
private struct RECT
{
public readonly int Left;
public readonly int Top;
public readonly int Right;
public readonly int Bottom;
public Point Location
{
get { return new Point(Left, Top); }
}
}
#endregion
#endregion
private ComboBoxEx owner;
static ACWindow()
{
ACWindows = new Dictionary<IntPtr, ACWindow>();
owners = new List<ComboBoxEx>();
}
/// <summary>
/// Creates a new ACWindow instance from a specific window handle.
/// </summary>
private ACWindow(IntPtr handle)
{
AssignHandle(handle);
}
/// <summary>
/// Registers a ComboBoxEx for adjusting the Complete Dropdown window size.
/// </summary>
public static void RegisterOwner(ComboBoxEx owner)
{
if ((owners.Contains(owner)))
{
return;
}
owners.Add(owner);
EnumThreadWindows(GetCurrentThreadId(), EnumThreadWindowCallback, IntPtr.Zero);
}
/// <summary>
/// This callback will receive the handle for each window that is
/// associated with the current thread. Here we match the drop down window name
/// to the drop down window name and assign the top window to the collection
/// of auto complete windows.
/// </summary>
private static bool EnumThreadWindowCallback(IntPtr hWnd, IntPtr lParam)
{
if ((GetClassName(hWnd) == "Auto-Suggest Dropdown"))
{
IntPtr handle = GetAncestor(hWnd, GA_ROOT);
if ((!ACWindows.ContainsKey(handle)))
{
ACWindows.Add(handle, new ACWindow(handle));
}
}
return true;
}
/// <summary>
/// Gets the class name for a specific window handle.
/// </summary>
private static string GetClassName(IntPtr hRef)
{
var lpClassName = new StringBuilder(256);
GetClassName(hRef, lpClassName, 256);
return lpClassName.ToString();
}
/// <summary>
/// Overrides the NativeWindow's WndProc to handle when the window
/// attributes changes.
/// </summary>
protected override void WndProc(ref Message m)
{
if ((m.Msg == WM_WINDOWPOSCHANGED))
{
// If the owner has not been set we need to find the ComboBoxEx that
// is associated with this dropdown window. We do it by checking if
// the upper-left location of the drop-down window is within the
// ComboxEx client rectangle.
if ((owner == null))
{
Rectangle ownerRect = default(Rectangle);
var acRect = new RECT();
foreach (ComboBoxEx cbo in owners)
{
GetWindowRect(Handle, ref acRect);
ownerRect = cbo.RectangleToScreen(cbo.ClientRectangle);
if ((ownerRect.Contains(acRect.Location)))
{
owner = cbo;
break; // TODO: might not be correct. Was : Exit For
}
}
owners.Remove(owner);
}
if (((owner != null)))
{
SetWindowPos(Handle, IntPtr.Zero, -5, 0, owner.AutoCompleteDropDownWidth,
owner.AutoCompleteDropDownHeight, SWP_NOMOVE | SWP_NOZORDER | SWP_NOACTIVATE);
}
}
if ((m.Msg == WM_NCDESTROY))
{
ACWindows.Remove(Handle);
}
base.WndProc(ref m);
}
}
#endregion
}
这就是我所做的，实际上效果很好。很高兴最后找到答案:)
【讨论】：
此答案是对 reggie 答案的补充。
如果您希望用户能够调整自动完成下拉菜单的大小，请在 WndProc 方法中添加以下代码：
private const int WM_SIZING = 0x214;
if (m.Msg == WM_SIZING) {
if (owner != null) {
RECT rr = (RECT) Marshal.PtrToStructure(m.LParam, typeof(RECT));
owner.acDropDownWidth = (rr.Right - rr.Left);
owner.acDropDownHeight = (rr.Bottom - rr.Top);
}
}
【讨论】：
这样做是一个糟糕的设计决定。为什么不将其设置为静态大尺寸开始呢？您始终可以使用其中一个事件来获取文本宽度，然后使用它来设置组合框宽度。可能是onPaint？更简单的方法可能是创建您自己的从组合框继承的组合框类，然后自己重写方法来执行此操作。
【讨论】：