C#

public class FormatProviderFormat : IFormatProvider, ICustomFormatter
    {
        public object GetFormat(Type formatType)
        {
            if (formatType == typeof(ICustomFormatter))
            {
                return this;
            }
            else
            {
                return null;
            }
        }

        public string Format(string format, object arg, IFormatProvider formatProvider)
        {
            switch (format)
            {
                case "A":
                    return "AA";
                case "B":
                    return "BB";
                default:
                    return "CC";
                    break;
            }
        }
    }

DateTime dt = DateTime.Now;
IFormatProvider fpFormat = new FormatProviderFormat();
Console.WriteLine(String.Format(fpFormat, "{0:A} {0:B} {0}", dt));

AA BB CC

public class FormatProviderToString: IFormatProvider, IFormattable
    {
        public object GetFormat(Type formatType)
        {
            if (formatType == typeof(IFormattable))
            {
                return this;
            }
            else
            {
                return null;
            }
        }

        public string ToString(string format, IFormatProvider formatProvider)
        {
            switch (format)
            {
                case "A":
                    return "AA";
                case "B":
                    return "BB";
                default:
                    return "CC";
                    break;
            }
        }
    }

int i = 123;
IFormatProvider fpToString = new FormatProviderToString();
Console.WriteLine(i.ToString("A", fpToString) + " " + i.ToString("B", fpToString) + " " + i.ToString(fpToString));

var dIndex = new Dictionary<int, int>()// the key is the id of the object and the value is the index of the object into the bindinglist;

int id = thisObject.ID;
if(dIndex.ContainsKey(id))
{
  data.RemoveAt(dIndex[id]);//this is removing the item from bindinglist
  _dIndex.remove(id);
  
  foreach(var key in dIndex.keys)
  {
     if(dIndex[key] > id)
     {
        dIndex[Key]--;
     }
  }
}

private void cboBox1_SelectedIndexChanged(object sender, EventArgs e)

private void pn.cboBox1_SelectedIndexChanged(object sender, EventArgs e)

string Files = ListBox1.SelectedValue;
            byte[] fileBytes = System.IO.File.ReadAllBytes(Files);

            WebClient User = new WebClient();
            byte[] FileBuffer = User.DownloadData(Files);

            if (FileBuffer != null)
            {
                System.Web.HttpContext context = System.Web.HttpContext.Current;
                context.Response.Clear();
                context.Response.ClearHeaders();
                context.Response.ClearContent();
                context.Response.ContentType = "application/octet-stream";
                context.Response.AddHeader("content-length", FileBuffer.Length.ToString());
                context.Response.AppendHeader("Content-Disposition", "attachment; filename=" + Path.GetFileName(Files));
                context.Response.BinaryWrite(FileBuffer);
                context.ApplicationInstance.CompleteRequest();