0201 Uso de combobox en Visual Studio

Crear el programa Esponja05, como aplicación de windows form, y soltar dos combobox en diseño como en a figura, luego en form load colocar el código de color rojo

using System.Data;
using System.Drawing;
using System.Linq;
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 Esponja05
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            this.Text = DateTime.Now.ToString();
            comboBox1.Items.Clear();
            comboBox2.Items.Clear();
            for (int a = 0; a < 27; a++)
                comboBox1.Items.Add(a.ToString());
            string cad = "aeiou";
            foreach(char c in cad)
                comboBox2.Items.Add(c.ToString());

        }
    }
}

Ejercicio 01: poner un tercer combo y colocar todas las letras del alfabeto 

Solución en comentario en el blog

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 Esponja05
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            this.Text = DateTime.Now.ToString();
            comboBox1.Items.Clear();
            comboBox2.Items.Clear();
            for (int a = 0; a < 27; a++)
                comboBox1.Items.Add(a.ToString());
            string cad = "aeiou";
            foreach(char c in cad)
                comboBox2.Items.Add(c.ToString());
            for (char c='a';c<='z';c++)
                comboBox3.Items.Add(c.ToString());
        }
    }
}

Ejercicio 02: poner un  cuarto combo y colocar la tabla de multiplicar del 9 

Solución:

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 Esponja05
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            this.Text = DateTime.Now.ToString();
            comboBox1.Items.Clear();
            comboBox2.Items.Clear();
            for (int a = 0; a < 27; a++)
                comboBox1.Items.Add(a.ToString());
            string cad = "aeiou";
            foreach(char c in cad)
                comboBox2.Items.Add(c.ToString());
            for (char c='a';c<='z';c++)
                comboBox3.Items.Add(c.ToString());
            for (char c = 'a'; c <= 'z'; c++)
                comboBox3.Items.Add(c.ToString());
            for (int b=1; b<11;b++)
                comboBox4.Items.Add(b.ToString()+" * 9 = "+(9*b).ToString());
        }
    }
}