Getting Started with Windows Forms ComboDropDown

18 Nov 201810 minutes to read

ComboDropDown can host any Windows Forms control in its drop-down area. This section explains how to get started with the WinForms ComboDropDown control by hosting a TreeView control in its drop-down, which is one of the most common use cases.

Assembly deployment

Refer to the Control Dependencies section for the list of assemblies and NuGet packages required to use the ComboDropDown control.

Refer to NuGet Packages to learn how to install NuGet packages in a Windows Forms application.

To install the required NuGet package using the NuGet Package Manager Console, run the following command:

Install-Package Syncfusion.Shared.Base

Adding ComboDropDown via Designer

  1. Add the Syncfusion.Shared.Base assembly reference to the project.

  2. Create a new Windows Forms application in Visual Studio. Then, drag a ComboDropDown control and a TreeView control from the Toolbox onto the form.

Create new application

Drag and drop ComboDropDown and TreeView controls

  1. Add a few TreeNode entries to the TreeView control, either through the Properties window or in code. Set the TreeView.HideSelection property to false so that the selected node remains highlighted when the TreeView loses focus.

Set HideSelection property to false

  1. Select the ComboDropDown control, and in the Properties window, set the PopupControl property to the TreeView control.

Set the PopupControl property to the TreeView

NOTE: To enable two-way interaction between the ComboDropDown and the TreeView controls, where selecting a node updates the text and editing the text selects a node, refer to Setting Interaction between ComboDropDown and TreeView.

Adding ComboDropDown through code

Add the ComboDropDown control programmatically by following the steps below.

  1. Add the Syncfusion.Shared.Base assembly reference to the project and include the Syncfusion.Windows.Forms.Tools namespace in the code.

    using Syncfusion.Windows.Forms.Tools;
    Imports Syncfusion.Windows.Forms.Tools

  2. Create an instance of the ComboDropDown control.

    private Syncfusion.Windows.Forms.Tools.ComboDropDown comboDropDown1;
    this.comboDropDown1 = new Syncfusion.Windows.Forms.Tools.ComboDropDown();
    Private comboDropDown1 As Syncfusion.Windows.Forms.Tools.ComboDropDown
    Me.comboDropDown1 = New Syncfusion.Windows.Forms.Tools.ComboDropDown()

  3. Initialize the TreeView control with sample nodes, and then assign it to the PopupControl property of the ComboDropDown control.

// Populate the TreeView with sample nodes
       this.treeView1.Nodes.Add("Root");
       this.treeView1.Nodes[0].Nodes.Add("Child 1");
       this.treeView1.Nodes[0].Nodes.Add("Child 2");
       this.treeView1.HideSelection = false;
   
       // Host the TreeView in the ComboDropDown's popup
       this.comboDropDown1.PopupControl = this.treeView1;
' Populate the TreeView with sample nodes
       Me.treeView1.Nodes.Add("Root")
       Me.treeView1.Nodes(0).Nodes.Add("Child 1")
       Me.treeView1.Nodes(0).Nodes.Add("Child 2")
       Me.treeView1.HideSelection = False
   
       ' Host the TreeView in the ComboDropDown's popup
       Me.comboDropDown1.PopupControl = Me.treeView1
  1. Add the ComboDropDown and TreeView controls to the form’s Controls collection.
this.Controls.Add(this.comboDropDown1);
       this.Controls.Add(this.treeView1);
Me.Controls.Add(Me.comboDropDown1)
       Me.Controls.Add(Me.treeView1)

Complete Code Example

The following example combines all the preceding steps into a single runnable application.

using Syncfusion.Windows.Forms.Tools;
   
   public partial class Form1 : Form
   {
       private Syncfusion.Windows.Forms.Tools.ComboDropDown comboDropDown1;
       private System.Windows.Forms.TreeView treeView1;
   
       public Form1()
       {
           InitializeComponent();
   
           this.comboDropDown1 = new Syncfusion.Windows.Forms.Tools.ComboDropDown();
           this.treeView1 = new TreeView();
   
           this.comboDropDown1.Location = new System.Drawing.Point(20, 20);
           this.comboDropDown1.Size = new System.Drawing.Size(200, 21);
   
           // Populate the TreeView with sample nodes
           this.treeView1.Nodes.Add("Root");
           this.treeView1.Nodes[0].Nodes.Add("Child 1");
           this.treeView1.Nodes[0].Nodes.Add("Child 2");
           this.treeView1.HideSelection = false;
   
           // Host the TreeView in the ComboDropDown's popup
           this.comboDropDown1.PopupControl = this.treeView1;
   
           this.Controls.Add(this.comboDropDown1);
           this.Controls.Add(this.treeView1);
       }
   }
Imports Syncfusion.Windows.Forms.Tools
   
   Public Partial Class Form1
       Inherits System.Windows.Forms.Form
   
       Private comboDropDown1 As Syncfusion.Windows.Forms.Tools.ComboDropDown
       Private treeView1 As System.Windows.Forms.TreeView
   
       Public Sub New()
           InitializeComponent()
   
           Me.comboDropDown1 = New Syncfusion.Windows.Forms.Tools.ComboDropDown()
           Me.treeView1 = New TreeView()
   
           Me.comboDropDown1.Location = New System.Drawing.Point(20, 20)
           Me.comboDropDown1.Size = New System.Drawing.Size(200, 21)
   
           ' Populate the TreeView with sample nodes
           Me.treeView1.Nodes.Add("Root")
           Me.treeView1.Nodes(0).Nodes.Add("Child 1")
           Me.treeView1.Nodes(0).Nodes.Add("Child 2")
           Me.treeView1.HideSelection = False
   
           ' Host the TreeView in the ComboDropDown's popup
           Me.comboDropDown1.PopupControl = Me.treeView1
   
           Me.Controls.Add(Me.comboDropDown1)
           Me.Controls.Add(Me.treeView1)
       End Sub
   End Class