Hi Rajani Kanth,
You can handle BeforeAddItem event of AutoComplete and set the items of ListBox as shown below:
private void autoComplete1_BeforeAddItem(object sender, Syncfusion.Windows.Forms.Tools.AutoCompleteAddItemCancelEventArgs args)
{
this.listBox1.Items.AddRange (args.RowItem.ItemArray );
}
If you do not want the DropDownList in AutoSuggestMode or suppress the DropDown as you said,then you can set AutoCompleteModes to AutoAppend.
this.autoComplete1.SetAutoComplete(this.textBox1, Syncfusion.Windows.Forms.Tools.AutoCompleteModes.AutoAppend);
Please take a look at the sample attached and let me know if you need furthur assistance.
Sample
Thanks for your continued interest in Syncfusion products.
Regards,
Anu.