.Net – Type and Search ListBox

The Type and Search feature in not available out of the box for System.Windows.Forms.CheckedListBox or System.Windows.Forms.ListBox controls in .net. So, I thought to just share a simple trick with which this could be easily managed.

We can take two approaches to achieve this -

1. Either we can go for creating a Custom control for this.
2. And if this feature is not required at a general level, we can implement the functionality at the form/user control level.

Now, without talking much on this, I will take you straight away to the implementation -

The below is the code generated by the designer followed by the code to be written to make the type and search work -

partial class FrmTypeAndSearchListBox

  {

    /// <summary>

    /// Required designer variable.

    /// </summary>

    private System.ComponentModel.IContainer components = null;

    /// <summary>

    /// Clean up any resources being used.

    /// </summary>

    /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>

    protected override void Dispose(bool disposing)

    {

      if (disposing && (components != null))

      {

        components.Dispose();

      }

      base.Dispose(disposing);

    }

    #region Windows Form Designer generated code

    /// <summary>

    /// Required method for Designer support - do not modify

    /// the contents of this method with the code editor.

    /// </summary>

    private void InitializeComponent()

    {

      this.lstBxTypeNSearch = new System.Windows.Forms.ListBox();

      this.SuspendLayout();

      // 

      // lstBxTypeNSearch

      // 

      this.lstBxTypeNSearch.FormattingEnabled = true;

      this.lstBxTypeNSearch.Items.AddRange(new object[] {

            "Aashay",

            "Aashish",

            "Abdul-Azeez",

            "Abdul-Baari",

            "Abdullah",

            "Abeer",

            "Achal",

            "Achalendra",

            "Achintya",

            "Achyut",

            "Acyutaraya",

            "Adalarasu",

            "Adarsh",

            "Agrim",

            "Agriya",

            "Ahmad",

            "Ahsan",

            "Aja",

            "Ajaat",

            "Ajaatshatru",

            "Ajamil",

            "Akhil",

            "Akhilesh",

            "Akmal",

            "Akram",

            "Akroor",

            "Akshan",

            "Aloke",

            "Amal",

            "Amalendu",

            "Angad",

            "Angamuthu",

            "Anil",

            "Arivunambi",

            "Avinash",

            "Azhagar",

            "Azhar",

            "Azzam"});

      this.lstBxTypeNSearch.Location = new System.Drawing.Point(52, 47);

      this.lstBxTypeNSearch.Name = "lstBxTypeNSearch";

      this.lstBxTypeNSearch.Size = new System.Drawing.Size(146, 108);

      this.lstBxTypeNSearch.TabIndex = 14;

      this.lstBxTypeNSearch.KeyDown += new System.Windows.Forms.KeyEventHandler(this.lstBxTypeNSearch_KeyDown);

      // 

      // FrmTypeAndSearchListBox

      // 

      this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);

      this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;

      this.ClientSize = new System.Drawing.Size(292, 266);

      this.Controls.Add(this.lstBxTypeNSearch);

      this.Name = "FrmTypeAndSearchListBox";

      this.Text = "FrmTypeAndSearchListBox";

      this.ResumeLayout(false);

    }

    #endregion

    private System.Windows.Forms.ListBox lstBxTypeNSearch;

  }

public partial class FrmTypeAndSearchListBox : Form

  {

    DateTime lastKeyDownOnListBox; //DateTime of the last KeyDown on the ListBox.

    StringBuilder listBoxFindString; //String to find in the ListBox.

    int resetListBoxFindStringAfter; //Milliseconds after which the FindString should be reset.

    int findStartIndex; //Starting index from where to find from.

    public FrmTypeAndSearchListBox()

    {

      InitializeComponent();

      //Initializing with current DateTime.

      lastKeyDownOnListBox = DateTime.Now;

      //Initialising the FindString with Empty.

      listBoxFindString = new StringBuilder(string.Empty);

      //Setting 250ms as the reset interval.

      resetListBoxFindStringAfter = 250;

      //Setting to -1 to start from the begining.

      findStartIndex = -1;

    }

    private void lstBxTypeNSearch_KeyDown(object sender, KeyEventArgs e)

    {

      //Just incase the same handler is bound to multiple controls

      //inheriting from ListBox class.

      ListBox senderListBox = sender as ListBox;

      if (senderListBox != null)

      {

        switch (e.KeyData.ToString())

        {

          case "Down":

          case "Up":

          case "Right":

          case "Left":

            //Add on the cases for the keys which we do not want to handle.

            break;

          default:

            //Reset the FindString if the gap between two key strokes exceeds the specified limit.

            if (DateTime.Now.Subtract(lastKeyDownOnListBox).Milliseconds > resetListBoxFindStringAfter)

            { listBoxFindString.Clear(); }

            //Set the DateTime of the current key stroke.

            lastKeyDownOnListBox = DateTime.Now;

            //Prepare the Find String.

            listBoxFindString.Append(e.KeyData.ToString());

            //Find the matching index if any.

            int matchedIndex = senderListBox.FindString(listBoxFindString.ToString(),

                                                        findStartIndex);

            //Select the Item if a match is found.

            if (matchedIndex > 0)

            { senderListBox.SelectedIndex = matchedIndex; }

            break;

        } 

      }

    }

  }

The above code is well commented. Still, if I have missed anything please feel free to revert with your comment. Hope, this small trick will prove to be helpful.