我在文本框上使用AutoComplete属性（实际上是ToolStripTextBox）。这工作正常，除非我输入至少一个字符才会显示。即使文本框为空，如何显示建议？
Mode = Suggest
Source = CustomSource
源设置为progamatically并限制为10个项目
或者，如果有人知道如何强制建议以编程方式显示可能是解决方案的OnEnter事件
答案 0 :(得分：4)
考虑到这是 hack 。我设法解决了这个问题，缺乏API功能，做了一件微不足道的事情。我会用代码告诉你：
dim source as AutoCompleteStringCollection = new AutoCompleteStringColection()
dim values() as String = new String() {" Monday", _
" Tuesday", _
" Wednesday", _
" Thursday", _
" Friday", _
" Saturday", _
" Sunday" }
TextBox1.AutoCompleteMode = AutoCompleteMode.SuggestAppend
TextBox1.AutoCompleteSource = AutoCompleteSource.CustomSource
TextBox1.AutoCompleteCustomSource = source
也就是说，在自动完成列表中的每个字符串前面加一个空格。然后，这是你对这一事实的了解，并将其用于您的方便目标。
例如，您可以在单击，聚焦等时在TextBox中添加空格。（请注意，这可以使用任何字符完成。想法是知道自动完成列表中的每个字符串都以相同的角色）
你必须要注意这一点。实际上，请考虑扩展TextBox表单并管理对输入字符串的正确修剪。
再一次，这个推荐或不推荐是由你自己决定的。这个答案倾向于做的是解决想要TextBox下降建议列表而不开始输入API限制的问题，也称为解决方法或丑陋黑客
答案 1 :(得分：3)
我不确定是否有任何解决方案，特别是因为如果您删除TextBox中的所有文字，建议框会自动关闭。
解决方法可能是ComboBox与TextBox重叠，您可以显示所有选项，但如果选择了其中一个选项，或者输入了某些内容，则会自动切换到{{1}并显示相反。
虽然我建议在这种情况下我可能会考虑完全摆脱TextBox而只是坚持TextBox，因为那就是它的用途。
要以ComboBox ComboBox查看SendMessage API和消息CB_SHOWDROPDOWN，以编程方式显示下拉列表（如果我没记错的话，您可以使用相同的API /消息，但参数不同如果需要的话，以编程方式关闭它。
答案 2 :(得分：2)
解决方案是直接包装并调用AutoSuggest WinShell函数。然后，您可以启用此功能而不必担心太多（甚至免费获得一些额外的帮助）。
下面是一个有效的示例，即使您在框中未键入任何内容（当用户按下向上/向下箭头时），您也可以显示AutoSuggest列表
与本要点中的代码相同：https://gist.github.com/sverrirs/e6a64faaab341882c3e801792f5e87ae
public void EnableAutoSuggest(TextBox tb, string[] suggestions) {
// Try to enable a more advanced settings for AutoComplete via the WinShell interface
try {
var source = new SourceCustomList() {StringList = suggestions.ToArray()};
// For options descriptions see:
// https://docs.microsoft.com/en-us/windows/desktop/api/shldisp/ne-shldisp-_tagautocompleteoptions
var options = AUTOCOMPLETEOPTIONS.ACO_UPDOWNKEYDROPSLIST | AUTOCOMPLETEOPTIONS.ACO_USETAB |
AUTOCOMPLETEOPTIONS.ACO_AUTOAPPEND | AUTOCOMPLETEOPTIONS.ACO_AUTOSUGGEST;
AutoCompleteExt.Enable(tb.Handle, source, options);
}
catch (Exception) {
// Incase of an error, let's fall back to the default
var source = new AutoCompleteStringCollection();
source.AddRange(suggestions);
tb.AutoCompleteMode = AutoCompleteMode.SuggestAppend;
tb.AutoCompleteSource = AutoCompleteSource.CustomSource;
tb.AutoCompleteCustomSource = source;
}
}
public void DisableAutoSuggest(TextBox tb) {
tb.AutoCompleteCustomSource = null;
AutoCompleteExt.Disable(tb.Handle);
}
以及AutoCompleteExt的实现
using System;
using System.Runtime.InteropServices;
/// <summary>
/// From: https://www.codeproject.com/Articles/3792/C-does-Shell-Part-4
/// Note: The UCOMIEnumString interface is deprecated in .NET as of 2018!
/// </summary>
public class AutoCompleteExt {
public static Guid CLSID_AutoComplete = new Guid("{00BB2763-6A77-11D0-A535-00C04FD7D062}");
private static object GetAutoComplete()
{
return Activator.CreateInstance(Type.GetTypeFromCLSID(CLSID_AutoComplete));
}
public static void Enable(IntPtr controlHandle, SourceCustomList items, AUTOCOMPLETEOPTIONS options) {
if (controlHandle == IntPtr.Zero)
return;
IAutoComplete2 iac = null;
try {
iac = (IAutoComplete2) GetAutoComplete();
int ret = iac.Init(controlHandle, items, "", "");
ret = iac.SetOptions(options);
ret = iac.Enable(true);
}
finally {
if (iac != null)
Marshal.ReleaseComObject(iac);
}
}
public static void Disable(IntPtr controlHandle) {
if (controlHandle == IntPtr.Zero)
return;
IAutoComplete2 iac = null;
try {
iac = (IAutoComplete2) GetAutoComplete();
iac.Enable(false);
}
finally {
if (iac != null)
Marshal.ReleaseComObject(iac);
}
}
}
/// <summary>
/// From https://www.pinvoke.net/default.aspx/Interfaces.IAutoComplete2
/// </summary>
[ComImport]
[InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
[Guid("EAC04BC0-3791-11D2-BB95-0060977B464C")]
public interface IAutoComplete2 {
[PreserveSig]
int Init(
// Handle to the window for the system edit control that is to
// have autocompletion enabled.
IntPtr hwndEdit,
// Pointer to the IUnknown interface of the string list object that
// is responsible for generating candidates for the completed
// string. The object must expose an IEnumString interface.
[MarshalAs(UnmanagedType.IUnknown)] object punkACL,
// Pointer to an optional null-terminated Unicode string that gives
// the registry path, including the value name, where the format
// string is stored as a REG_SZ value. The autocomplete object
// first looks for the path under HKEY_CURRENT_USER . If it fails,
// it then tries HKEY_LOCAL_MACHINE . For a discussion of the
// format string, see the definition of pwszQuickComplete.
[MarshalAs(UnmanagedType.LPWStr)] string pwszRegKeyPath,
// Pointer to an optional string that specifies the format to be
// used if the user enters some text and presses CTRL+ENTER. Set
// this parameter to NULL to disable quick completion. Otherwise,
// the autocomplete object treats pwszQuickComplete as a sprintf
// format string, and the text in the edit box as its associated
// argument, to produce a new string. For example, set
// pwszQuickComplete to "http://www. %s.com/". When a user enters
// "MyURL" into the edit box and presses CTRL+ENTER, the text in
// the edit box is updated to "http://www.MyURL.com/".
[MarshalAs(UnmanagedType.LPWStr)] string pwszQuickComplete
);
// Enables or disables autocompletion.
[PreserveSig]
int Enable(bool value);
// Sets the current autocomplete options.
[PreserveSig]
int SetOptions(AUTOCOMPLETEOPTIONS dwFlag);
// Retrieves the current autocomplete options.
[PreserveSig]
int GetOptions(out AUTOCOMPLETEOPTIONS pdwFlag);
}
/// <summary>
/// Specifies values used by IAutoComplete2::GetOptions and
/// "IAutoComplete2.SetOptions" for options surrounding autocomplete.
/// </summary>
/// <remarks>
/// [AUTOCOMPLETEOPTIONS Enumerated Type ()]
/// http://msdn.microsoft.com/en-us/library/bb762479.aspx
/// </remarks>
[Flags]
public enum AUTOCOMPLETEOPTIONS {
/// <summary>Do not autocomplete.</summary>
ACO_NONE = 0x0000,
/// <summary>Enable the autosuggest drop-down list.</summary>
ACO_AUTOSUGGEST = 0x0001,
/// <summary>Enable autoappend.</summary>
ACO_AUTOAPPEND = 0x0002,
/// <summary>Add a search item to the list of
/// completed strings. When the user selects
/// this item, it launches a search engine.</summary>
ACO_SEARCH = 0x0004,
/// <summary>Do not match common prefixes, such as
/// "www." or "http://".</summary>
ACO_FILTERPREFIXES = 0x0008,
/// <summary>Use the TAB key to select an
/// item from the drop-down list.</summary>
ACO_USETAB = 0x0010,
/// <summary>Use the UP ARROW and DOWN ARROW keys to
/// display the autosuggest drop-down list.</summary>
ACO_UPDOWNKEYDROPSLIST = 0x0020,
/// <summary>Normal windows display text left-to-right
/// (LTR). Windows can be mirrored to display languages
/// such as Hebrew or Arabic that read right-to-left (RTL).
/// Typically, control text is displayed in the same
/// direction as the text in its parent window. If
/// ACO_RTLREADING is set, the text reads in the opposite
/// direction from the text in the parent window.</summary>
ACO_RTLREADING = 0x0040,
/// <summary>[Windows Vista and later]. If set, the
/// autocompleted suggestion is treated as a phrase
/// for search purposes. The suggestion, Microsoft
/// Office, would be treated as "Microsoft Office"
/// (where both Microsoft AND Office must appear in
/// the search results).</summary>
ACO_WORD_FILTER = 0x0080,
/// <summary>[Windows Vista and later]. Disable prefix
/// filtering when displaying the autosuggest dropdown.
/// Always display all suggestions.</summary>
ACO_NOPREFIXFILTERING = 0x0100
}
/// <summary>
/// Implements the https://docs.microsoft.com/en-us/windows/desktop/api/objidl/nn-objidl-ienumstring
/// interface for autoccomplete
/// </summary>
public class SourceCustomList : UCOMIEnumString {
public string[] StringList;
private int currentPosition = 0;
public int Next(
int celt, // Number of elements being requested.
string[] rgelt, // Array of size celt (or larger) of the
// elements of interest. The type of this
// parameter depends on the item being
// enumerated.
out int pceltFetched) // Pointer to the number of elements actually
// supplied in rgelt. The Caller can pass
// in NULL if celt is 1.
{
pceltFetched = 0;
while ((currentPosition <= StringList.Length-1) && (pceltFetched<celt))
{
rgelt[pceltFetched] = StringList[currentPosition];
pceltFetched++;
currentPosition++;
}
if (pceltFetched == celt)
return 0; // S_OK;
else
return 1; // S_FALSE;
}
/// <summary>
/// This method skips the next specified number of elements in the enumeration sequence.
/// </summary>
/// <param name="celt"></param>
/// <returns></returns>
public int Skip(
int celt) // Number of elements to be skipped.
{
currentPosition += celt;
if (currentPosition <= StringList.Length-1)
return 0;
else
return 1;
}
// This method resets the enumeration sequence to the beginning.
public Int32 Reset()
{
currentPosition = 0;
return 0;
}
// This method creates another enumerator that contains the same enumeration
// state as the current one. Using this function, a client can record a
// particular point in the enumeration sequence and return to that point at a
// later time. The new enumerator supports the same interface as the original one.
public void Clone(
out UCOMIEnumString ppenum) // Address of the IEnumString pointer
// variable that receives the interface
// pointer to the enumeration object. If
// the method is unsuccessful, the value
// of this output variable is undefined.
{
SourceCustomList clone = new SourceCustomList {
currentPosition = currentPosition,
StringList = (String[]) StringList.Clone()
};
ppenum = clone;
}
}
答案 3 :(得分：1)
在.net api中没有这种可能性。在IAutoComplete shell接口中没有这种可能性.net正在内部使用。
所以你应该忍受它，或者在不使用默认行为的情况下实现你自己的自动完成行为。您可以按照之前的建议使用组合框下拉菜单，甚至可以创建自己的自动完成控件（在我的应用程序中，我选择了最后一个变体）。