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Posted 8 Mar 2014

IntelliSense TextBox in C#

, 10 Mar 2014
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Taking as base from IntelliSense TextBox in C#, created by Anand Gunasekaran, I decided to create a new user control inherithed from TextBox that provides automatically an IntelliSense-Like function without calling any method.

Using the code

Building the control

The new control must have two important components: a list of strings for containing all the words we want for autocomplete and a ListBox that will show all the words in the list.

List<string> dictionary;
ListBox listbox;

Then, let's make a constructor for the class that allow us put the control in the UI designer and, of course, initialize the inner ListBox in the new IntelliSenseTextBox.

public IntelliSenseTextBox() : base()
    listbox = new ListBox();
    listbox.Parent = this;
    listbox.KeyUp += OnKeyUp;
    listbox.Visible = false;
    this.dictionary = new List<string>();

After, we will override some methods of the TextBox, specifically OnKeyPress and OnTextChanged

protected override void OnKeyPress(KeyPressEventArgs e)
    if (e.KeyChar == (char)Keys.Enter || e.KeyChar == (char)Keys.Down)
        if (listbox.Visible == true)
        e.Handled = true;
    else if (e.KeyChar == (char)Keys.Escape)
        listbox.Visible = false;
        e.Handled = true;

protected override void OnTextChanged(EventArgs e)
    Point cp;
    GetCaretPos(out cp);
    List<string> lstTemp = new List<string>();

    listbox.SetBounds(cp.X + this.Left, cp.Y + this.Top + 20, 150, 50);
    var TempFilteredList = dictionary.Where(
             n => n.StartsWith(GetLastString(this.Text).ToUpper())).Select(r => r);

    lstTemp = TempFilteredList.ToList<string>();
    if (lstTemp.Count != 0 && GetLastString(this.Text) != "")
        listbox.DataSource = lstTemp;

Finally we must create the method to handle the KeyUp of the ListBox

private void OnKeyUp(object sender, KeyEventArgs e)
    if (e.KeyCode == Keys.Enter)
        string StrLS = GetLastString(this.Text);
        int LIOLS = this.Text.LastIndexOf(StrLS);
        string TempStr = this.Text.Remove(LIOLS);
        this.Text = TempStr + ((ListBox)sender).SelectedItem.ToString();
        this.Select(this.Text.Length, 0);

Using the control

Now our IntelliSenseTextBox is complete but, we need to specify which words will be in the dictionary

public partial class Form1 : Form
    List<string> ISList = new List<string>(new string[]{ 

    public Form1()
        this.intelliSenseTextBox1.Dictionary = ISList;

Points of Interest

When I saw the work of Anand Gunasekaran I was very interested in the topic so I decided to create this control for my school projects, specifically for a compiler in which a friend and I are working.


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Alain Peralta
Mexico Mexico
Great things come from rare ideas. Wink | ;)

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Comments and Discussions

QuestionA screenshot would be nice! Pin
Dmitri Nеstеruk10-Mar-14 1:07
memberDmitri Nеstеruk10-Mar-14 1:07 
AnswerRe: A screenshot would be nice! Pin
thatraja10-Mar-14 1:21
protectorthatraja10-Mar-14 1:21 
AnswerRe: A screenshot would be nice! Pin
Alain Peralta10-Mar-14 11:27
memberAlain Peralta10-Mar-14 11:27 
Questionthere got a bug Pin
Cosmic_Spy9-Mar-14 7:16
memberCosmic_Spy9-Mar-14 7:16 
AnswerRe: there got a bug Pin
Alain Peralta9-Mar-14 7:30
memberAlain Peralta9-Mar-14 7:30 
GeneralRe: I found solution! Pin
zidanetan20-Aug-15 18:27
memberzidanetan20-Aug-15 18:27 

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