如何设置Lookup字段的值, 首先我们同样需要了解SPFieldLookupValueCollection和SPFieldLookupValue, 这2个类的原理和之前所讲解到SPFieldUserValueCollection一样,这里就不多讲解

/// <summary>
        /// Convert dropdownList value to SPFieldLookupValue
        /// </summary>
        /// <param name="dropdownList">DropDownList Control</param>
        /// <returns>SPFieldLookupValue</returns>
        private SPFieldLookupValue setLookupValue(DropDownList dropdownList)
        {
            SPFieldLookupValue lookupValue = new SPFieldLookupValue(Convert.ToInt32(dropdownList.SelectedItem.Value), dropdownList.SelectedItem.Text);
            return lookupValue;
        }