C# AutoComplete
The existing AutoComplete functionality only supports searching by prefix. There doesn't seem to be any decent way to override the behavior.
Some people have implemented their own autocomplete functions by overriding the OnTextChanged event. That's probably your best bet.
For example, you can add a ListBox just below the TextBox and set its default visibility to false. Then you can use the OnTextChanged event of the TextBox and the SelectedIndexChanged event of the ListBox to display and select items.
This seems to work pretty well as a rudimentary example:
public Form1()
{
InitializeComponent();
acsc = new AutoCompleteStringCollection();
textBox1.AutoCompleteCustomSource = acsc;
textBox1.AutoCompleteMode = AutoCompleteMode.None;
textBox1.AutoCompleteSource = AutoCompleteSource.CustomSource;
}
private void button1_Click(object sender, EventArgs e)
{
acsc.Add("[001] some kind of item");
acsc.Add("[002] some other item");
acsc.Add("[003] an orange");
acsc.Add("[004] i like pickles");
}
void textBox1_TextChanged(object sender, System.EventArgs e)
{
listBox1.Items.Clear();
if (textBox1.Text.Length == 0)
{
hideResults();
return;
}
foreach (String s in textBox1.AutoCompleteCustomSource)
{
if (s.Contains(textBox1.Text))
{
Console.WriteLine("Found text in: " + s);
listBox1.Items.Add(s);
listBox1.Visible = true;
}
}
}
void listBox1_SelectedIndexChanged(object sender, System.EventArgs e)
{
textBox1.Text = listBox1.Items[listBox1.SelectedIndex].ToString();
hideResults();
}
void listBox1_LostFocus(object sender, System.EventArgs e)
{
hideResults();
}
void hideResults()
{
listBox1.Visible = false;
}
There's a lot more you could do without too much effort: append text to the text box, capture additional keyboard commands, and so forth.
If you decide to use a query that is based on user input make sure you use SqlParameters to avoid SQL Injection attacks
SqlCommand sqlCommand = new SqlCommand();
sqlCommand.CommandText = "SELECT Name from view_customers where Details LIKE '%" + @SearchParam + "%'";
sqlCommand.Parameters.AddWithValue("@SearchParam", searchParam);
Here's an implementation that inherits the ComboBox control class, rather than replacing the whole combo-box with a new control. It displays its own drop-down when you type in the text box, but clicking to show the drop-list is handled as before (i.e. not with this code). As such you get that proper native control and look.
Please use it, modify it and edit the answer if you would like to improve it!
class ComboListMatcher : ComboBox, IMessageFilter
{
private Control ComboParentForm; // Or use type "Form"
private ListBox listBoxChild;
private int IgnoreTextChange;
private bool MsgFilterActive = false;
public ComboListMatcher()
{
// Set up all the events we need to handle
TextChanged += ComboListMatcher_TextChanged;
SelectionChangeCommitted += ComboListMatcher_SelectionChangeCommitted;
LostFocus += ComboListMatcher_LostFocus;
MouseDown += ComboListMatcher_MouseDown;
HandleDestroyed += ComboListMatcher_HandleDestroyed;
}
void ComboListMatcher_HandleDestroyed(object sender, EventArgs e)
{
if (MsgFilterActive)
Application.RemoveMessageFilter(this);
}
~ComboListMatcher()
{
}
private void ComboListMatcher_MouseDown(object sender, MouseEventArgs e)
{
HideTheList();
}
void ComboListMatcher_LostFocus(object sender, EventArgs e)
{
if (listBoxChild != null && !listBoxChild.Focused)
HideTheList();
}
void ComboListMatcher_SelectionChangeCommitted(object sender, EventArgs e)
{
IgnoreTextChange++;
}
void InitListControl()
{
if (listBoxChild == null)
{
// Find parent - or keep going up until you find the parent form
ComboParentForm = this.Parent;
if (ComboParentForm != null)
{
// Setup a messaage filter so we can listen to the keyboard
if (!MsgFilterActive)
{
Application.AddMessageFilter(this);
MsgFilterActive = true;
}
listBoxChild = listBoxChild = new ListBox();
listBoxChild.Visible = false;
listBoxChild.Click += listBox1_Click;
ComboParentForm.Controls.Add(listBoxChild);
ComboParentForm.Controls.SetChildIndex(listBoxChild, 0); // Put it at the front
}
}
}
void ComboListMatcher_TextChanged(object sender, EventArgs e)
{
if (IgnoreTextChange > 0)
{
IgnoreTextChange = 0;
return;
}
InitListControl();
if (listBoxChild == null)
return;
string SearchText = this.Text;
listBoxChild.Items.Clear();
// Don't show the list when nothing has been typed
if (!string.IsNullOrEmpty(SearchText))
{
foreach (string Item in this.Items)
{
if (Item != null && Item.Contains(SearchText, StringComparison.CurrentCultureIgnoreCase))
listBoxChild.Items.Add(Item);
}
}
if (listBoxChild.Items.Count > 0)
{
Point PutItHere = new Point(this.Left, this.Bottom);
Control TheControlToMove = this;
PutItHere = this.Parent.PointToScreen(PutItHere);
TheControlToMove = listBoxChild;
PutItHere = ComboParentForm.PointToClient(PutItHere);
TheControlToMove.Show();
TheControlToMove.Left = PutItHere.X;
TheControlToMove.Top = PutItHere.Y;
TheControlToMove.Width = this.Width;
int TotalItemHeight = listBoxChild.ItemHeight * (listBoxChild.Items.Count + 1);
TheControlToMove.Height = Math.Min(ComboParentForm.ClientSize.Height - TheControlToMove.Top, TotalItemHeight);
}
else
HideTheList();
}
/// <summary>
/// Copy the selection from the list-box into the combo box
/// </summary>
private void CopySelection()
{
if (listBoxChild.SelectedItem != null)
{
this.SelectedItem = listBoxChild.SelectedItem;
HideTheList();
this.SelectAll();
}
}
private void listBox1_Click(object sender, EventArgs e)
{
var ThisList = sender as ListBox;
if (ThisList != null)
{
// Copy selection to the combo box
CopySelection();
}
}
private void HideTheList()
{
if (listBoxChild != null)
listBoxChild.Hide();
}
public bool PreFilterMessage(ref Message m)
{
if (m.Msg == 0x201) // Mouse click: WM_LBUTTONDOWN
{
var Pos = new Point((int)(m.LParam.ToInt32() & 0xFFFF), (int)(m.LParam.ToInt32() >> 16));
var Ctrl = Control.FromHandle(m.HWnd);
if (Ctrl != null)
{
// Convert the point into our parent control's coordinates ...
Pos = ComboParentForm.PointToClient(Ctrl.PointToScreen(Pos));
// ... because we need to hide the list if user clicks on something other than the list-box
if (ComboParentForm != null)
{
if (listBoxChild != null &&
(Pos.X < listBoxChild.Left || Pos.X > listBoxChild.Right || Pos.Y < listBoxChild.Top || Pos.Y > listBoxChild.Bottom))
{
this.HideTheList();
}
}
}
}
else if (m.Msg == 0x100) // WM_KEYDOWN
{
if (listBoxChild != null && listBoxChild.Visible)
{
switch (m.WParam.ToInt32())
{
case 0x1B: // Escape key
this.HideTheList();
return true;
case 0x26: // up key
case 0x28: // right key
// Change selection
int NewIx = listBoxChild.SelectedIndex + ((m.WParam.ToInt32() == 0x26) ? -1 : 1);
// Keep the index valid!
if (NewIx >= 0 && NewIx < listBoxChild.Items.Count)
listBoxChild.SelectedIndex = NewIx;
return true;
case 0x0D: // return (use the currently selected item)
CopySelection();
return true;
}
}
}
return false;
}
}