To bind the arraylist with dropdown open BindDdlWithArraylist.aspx.cs page and in pageload event add some items in arraylist which user need to bind with dropdown. Then add that arraylist with dropdown and debug the application.
Insert the following code in your code behind file to bind arraylist to dropdown.
protected void Page_Load(object sender, EventArgs e)
ArrayList Companies = new ArrayList();
Companies.Add("Tata Consultancy Services");
Companies.Add("Computer Science Corporation");
Companies.Add("Capgemini Pvt Ltd");
Companies.Add("Infosys India Pvt Ltd");
//This is optional if you want to add blank item at index 0.
ddlItCompanies.Items.Insert(0, new ListItem("", ""));
//Loop and add items from ArrayList.
foreach (object Company in Companies)
ddlItCompanies.Items.Add(new ListItem(Company.ToString(), Company.ToString()));
Now Debug the application and see the view,Here is the image for reference: