How to bind intellisense auto complete box with the list

namespace Auto
{
    public partial class AutoComplete : Form
    {
        public List str = new List();
        public AutoComplete()
        {
            str.Add("one");
            str.Add("two");
            str.Add("three");
            str.Add("four");
            str.Add("five");
            str.Add("six");
            InitializeComponent();
        }
    }
}

The above code should be in Auto.cs file

and where as in the Auto.designer.cs file you should do like this:
for (int i = 0; i < str.Count; i++)
            {
                this.textBox1.AutoCompleteCustomSource.Add(str[i]);
            }
            this.textBox1.AutoCompleteMode = System.Windows.Forms.AutoCompleteMode.Append;
            this.textBox1.AutoCompleteSource = System.Windows.Forms.AutoCompleteSource.CustomSource;
            this.textBox1.Location = new System.Drawing.Point(70, 12);
            this.textBox1.Name = "textBox1";
            this.textBox1.Size = new System.Drawing.Size(244, 20);
            this.textBox1.TabIndex = 0;

which should do the job?

this.textBox1.AutoCompleteCustomSource.AddRange(new string[] {
            "one",
            "two",
            "three",
            "four",
            "five",
            "six",
            "seven"});
            this.textBox1.AutoCompleteMode = System.Windows.Forms.AutoCompleteMode.Append;
            this.textBox1.AutoCompleteSource = System.Windows.Forms.AutoCompleteSource.CustomSource;

Instead of the string in the above code add  your list from which you want to get strings.