C#

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Runtime.InteropServices;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

namespace Combo
{

    public class Combo //:IDisposable
    {
        private System.Windows.Forms.ComboBox li = new System.Windows.Forms.ComboBox(); //object
        public event EventHandler SelectedIndexChanged;
        private object[] eventObject;

        public void Addselect(Control FormName, string name, int top, int left, int width, int height, string Text)
        {
            li.Top = top;
            li.Left = left;
            li.Width = width;
            li.Height = height;
            li.Name = name;
            li.FlatStyle = FlatStyle.Flat;
            li.Text = Text;
            li.IntegralHeight = false;
            li.MaxDropDownItems = 5;
            li.DropDownStyle = ComboBoxStyle.DropDown;
            li.Size = new System.Drawing.Size(136, 81);
            li.BackColor = System.Drawing.Color.DarkGray;
            FormName.Controls.Add(li);
            eventObject = new object[] { this, "SelectedIndexChanged" };
            li.SelectedIndexChanged += new EventHandler(li_SelectedIndexChanged);
        }

        private void li_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (SelectedIndexChanged != null) //You must test this.
            {
                SelectedIndexChanged(eventObject, null);
            }
        }

        public bool Enabled
        {
            get { return li.Enabled; }
            set { li.Enabled = value; }
        }
        public bool Visible
        {
            get { return li.Visible; }
            set { li.Visible = value; }
        }
        public void Addtocombobox(string [] arguments )
        {
            li.Items.AddRange(arguments);
        }
        public int  sindex()
        {

            int index;
            index = li.SelectedIndex;
            return index;
            
       }
}
    }

public int  sindex()
       {

           int index;
           index = li.SelectedIndex;
           return index;

      }

Error	1	Since 'Combo.Combo.sindex()' returns void, a return keyword must not be followed by an object expression	F:\SelectboxLibrary\SelectboxLibrary\Class1.cs	65	13	SelectboxLibrary

public interface TheInterface
{
    string iText { get; set; }
}

public class SimpleClass : TheInterface
{
    public string iText { get; set; }
}

SomeOtherClass.SomeMethod(this, "some string");

public void SomeMethod(TheInterface iFace, string someText)
{ 
    // okay let's make it do something trivial
    iFace.iText = someText; 
}