search data from data table using combobox

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C#

C#4.0

while key in a word, I want to bind the data from sql table and want to automatically come out the list on combobox

My code is here.Can't automatically show the list of data on combobox.
Help me.

 private void SearchItem(string item)
        { 
               DataSet data = new DataSet();
            DataTable table = new DataTable();
            data = logic.GetData_By_Desc("SearchbyProductDescription", item);
            table.Rows.Clear();            
            table = data.Tables[0];            
            cboSearch.DataSource = table;
            cboSearch.DisplayMember = "Description";
            cboSearch.ValueMember = "id";          
            cboSearch.DroppedDown = true;
}
private void cboSearch_KeyDown(object sender, KeyEventArgs e)
        {
            if (e.KeyValue == 13)
            {
                string item = cboSearch.Text;
                SearchItem(item);}

}

ttds