How to set the Height of the Drop-Down List in the ComboBox in C#? - GeeksforGeeks

30 Jun, 2019
In Windows Forms, ComboBox provides two different features in a single control, it means ComboBox works as both TextBox and ListBox. In ComboBox, only one item is displayed at a time and the rest of the items are present in the drop-down menu. You are allowed to set the height in pixels of the drop-down list in your ComboBox by using the DropDownHeight Property. You can set this property using two different methods:
1. Design-Time: It is the easiest method to set the DropDownHeight property of the ComboBox control using the following steps:
Step 1: Create a windows form as shown in the below image:Visual Studio -> File -> New -> Project -> WindowsFormApp
Step 2: Drag the ComboBox control from the ToolBox and drop it on the windows form. You are allowed to place a ComboBox control anywhere on the windows form according to your need.
Step 3: After drag and drop you will go to the properties of the ComboBox control to set the DropDownHeight property of the ComboBox.Output:
Output:
2. Run-Time: It is a little bit trickier than the above method. In this method, you can set the height of the drop-down list in the ComboBox programmatically with the help of given syntax:
public int DropDownHeight { get; set; }
Here, the value of this property is of System.Int32 type. It will throw an ArgumentException if the value of this property is less than one. Following steps are used to set the DropDownHeight Property of the ComboBox elements:
Step 1: Create a combobox using the ComboBox() constructor is provided by the ComboBox class.// Creating ComboBox using ComboBox class
ComboBox mybox = new ComboBox();

// Creating ComboBox using ComboBox class
ComboBox mybox = new ComboBox();

Step 2: After creating ComboBox, set the DropDownHeight property of the ComboBox provided by the ComboBox class.// Set DropDownHeight property of the combobox
mybox.DropDownHeight = 26;

// Set DropDownHeight property of the combobox
mybox.DropDownHeight = 26;

Step 3: And last add this combobox control to form using Add() method.// Add this ComboBox to form
this.Controls.Add(mybox);
Example:using System;using System.Collections.Generic;using System.ComponentModel;using System.Data;using System.Drawing;using System.Linq;using System.Text;using System.Threading.Tasks;using System.Windows.Forms;  namespace WindowsFormsApp14 {  public partial class Form1 : Form {      public Form1()    {        InitializeComponent();    }      private void Form1_Load(object sender, EventArgs e)    {        // Creating and setting the properties of label        Label l = new Label();        l.Location = new Point(222, 80);        l.Size = new Size(99, 18);        l.Text = "Select Id";          // Adding this label to the form        this.Controls.Add(l);          // Creating and setting the properties of comboBox        ComboBox mybox = new ComboBox();        mybox.Location = new Point(327, 77);        mybox.Size = new Size(216, 26);        mybox.MaxLength = 3;        mybox.DropDownStyle = ComboBoxStyle.DropDown;        mybox.DropDownHeight = 26;        mybox.Items.Add(240);        mybox.Items.Add(241);        mybox.Items.Add(242);        mybox.Items.Add(243);        mybox.Items.Add(244);          // Adding this ComboBox to the form        this.Controls.Add(mybox);    }}}Output:Before setting drop-down height:After setting drop-down height:
// Add this ComboBox to form
this.Controls.Add(mybox);

Example:
using System;using System.Collections.Generic;using System.ComponentModel;using System.Data;using System.Drawing;using System.Linq;using System.Text;using System.Threading.Tasks;using System.Windows.Forms;  namespace WindowsFormsApp14 {  public partial class Form1 : Form {      public Form1()    {        InitializeComponent();    }      private void Form1_Load(object sender, EventArgs e)    {        // Creating and setting the properties of label        Label l = new Label();        l.Location = new Point(222, 80);        l.Size = new Size(99, 18);        l.Text = "Select Id";          // Adding this label to the form        this.Controls.Add(l);          // Creating and setting the properties of comboBox        ComboBox mybox = new ComboBox();        mybox.Location = new Point(327, 77);        mybox.Size = new Size(216, 26);        mybox.MaxLength = 3;        mybox.DropDownStyle = ComboBoxStyle.DropDown;        mybox.DropDownHeight = 26;        mybox.Items.Add(240);        mybox.Items.Add(241);        mybox.Items.Add(242);        mybox.Items.Add(243);        mybox.Items.Add(244);          // Adding this ComboBox to the form        this.Controls.Add(mybox);    }}}
Output:
Before setting drop-down height:
After setting drop-down height:
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