AutoComplete Textbox

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Introduction

During work on a project, I needed to use a control having auto complete facility in it as user types. I realized that we can make use of the textbox control or combobox control for this purpose. Both controls can be used to filter records as a drop down list to show the best matches. I will demonstrate it using VB.NET. If someone needs a C# version, an online converter can be used. I will be discussing the addition and removal of item from the drop down list.

Prerequisites

Before reading this article, we need to be aware of two properties and an enumeration introduced by Microsoft in the .NET Framework 2.0 which is AutoCompleteCustomSource property, AutoCompleteMode property and AutoCompleteSource enumeration.

We should also have a look at AutoCompleteStringCollection class.

Design

An auto complete source is binded to the textbox’s AutoCompleteCustomSource property. It will help to filter the best fit records in the suggestion list.

'Item is filled either manually or from database
Dim lst As New List(Of String)

'AutoComplete collection that will help to filter keep the records.
Dim MySource As New AutoCompleteStringCollection()

Implementation

I have filled the source from the list named ‘lst’ at Form1_Load event. This list can be populated by the database as well.

Private Sub Form1_Load(ByVal sender As System.Object, _
	ByVal e As System.EventArgs) Handles MyBase.Load

    'Manually added some items
    lst.Add("apple")
    lst.Add("applle")
    lst.Add("appple")
    lst.Add("appplee")
    lst.Add("bear")
    lst.Add("pear")

    'Records binded to the AutocompleteStringCollection.
    MySource.AddRange(lst.ToArray)

    'this AutocompleteStringcollection binded to the textbox as custom
    'source.
    TextBox1.AutoCompleteCustomSource = MySource

    'Auto complete mode set to suggest append so that it will sugesst one
    'or more suggested completion strings it has bith ‘Suggest’ and
    '‘Append’ functionality
    TextBox1.AutoCompleteMode = AutoCompleteMode.SuggestAppend

    'Set to Custom source we have filled already
    TextBox1.AutoCompleteSource = AutoCompleteSource.CustomSource
End Sub

Operations on AutoCompleteSource

As I have discussed earlier that we will see how to add/ remove entry from the source, we have binded to the Textbox’s source.

The event uses this task to achieve is KeyDown event.

Here is the source with explanation:

Private Sub TextBox1_KeyDown(ByVal sender As System.Object, _
ByVal e As System.Windows.Forms.KeyEventArgs) Handles TextBox1.KeyDown

If e.KeyCode = Keys.Enter Then   ' On enter I planned to add it the list
     If Not lst.Contains(TextBox1.Text) Then  ' If item not present already
        ' Add to the source directly
         TextBox1.AutoCompleteCustomSource.Add(TextBox1.Text)
     End If
ElseIf e.KeyCode = Keys.Delete Then 'On delete key, planned to remove entry

' declare a dummy source
Dim coll As AutoCompleteStringCollection = TextBox1.AutoCompleteCustomSource

' remove item from new source
coll.Remove(TextBox1.Text)

' Bind the updates
TextBox1.AutoCompleteCustomSource = coll

' Clear textbox
TextBox1.Clear()

End If                   ' End of ‘KeyCode’ condition

End Sub

Conclusion

There are more details as to how the whole thing works. I feel this is a viable solution for an Auto-Complete TextBox and I hope you find it interesting.