how to insert selected item from combobox to gridview or list view

[yousof]

i have web page that contian combobox filled from table

 If CtvAct.GetRecords("Fill_ActivityTb") = True Then
                AcivityCombo.DataSource = CtvAct.MainDataset.Tables("tbOLActivity").DefaultView
                AcivityCombo.DataTextField = "ActivityName"
                AcivityCombo.DataValueField = "ActivityId"
                AcivityCombo.DataBind()

i want to select an item from these combobox and pass it to gridview or listview
please help me how can i do these