c# - HiddenField.Value 在我的自定义控件内回发时是一个空字符串

Question

我有一个带有隐藏字段的自定义控件。回发时我想获取存储在其中的值，但它始终是一个空字符串。有什么想法吗？

我正在对隐藏字段值执行客户端操作，并在发出回发之前在 firebug 中验证字段是否正确

这是设置:

public class DualListPanel : SWebControl, INamingContainer

    {

        protected IList<DlpItem> UnassignedList { get; set; }
        protected IList<DlpItem> AssignedList { get; set; }
        private HiddenField assignedItemsField, unassignedItemsField;

        public DualListPanel()
        {
            CssClass = "DualListPanel";
            EnableViewState = true;
        }

        #region ViewState

        protected override void LoadViewState(object savedState)
        {
            var state = savedState as object[];
            UnassignedList =   state[0] as List<DlpItem>;
            AssignedList = state[1] as List<DlpItem>;
            base.LoadViewState(state[2]);
        }

        protected override object SaveViewState()
        {
            object[] state = new object[3];
            state[0] = UnassignedList;
            state[1] = AssignedList;
            state[2] = base.SaveViewState();
            return state;
        }

        #endregion

        #region WebControl Overrides


        protected override void OnInit(EventArgs e)
        {
            EnsureChildControls();
            GetUnassignedList(); //omitted method
            GetAssignedList(); //omitted method
            base.OnInit(e);
        }

        protected override void CreateChildControls()
        {          
            assignedItemsField = new HiddenField();
            assignedItemsField.ID = "HiddenAssignedItems";
            assignedItemsField.EnableViewState = true;

            unassignedItemsField = new HiddenField();
            unassignedItemsField.ID = "HiddenUnassignedItems";
            unassignedItemsField.EnableViewState = true;

            Controls.Add(assignedItemsField);
            Controls.Add(unassignedItemsField);
            base.CreateChildControls();
        }

        #endregion

        #region Item Lists Retrieval

        public string GetCommaDelimUnassignedItems()
        {
            return unassignedItemsField.Value;
        }

        public string GetCommaDelimAssignedItems()
        {
            return assignedItemsField.Value;
        }

        #endregion
    }

Answer 1

我认为隐藏字段的值在回发期间不会丢失，每当您初始化隐藏字段时，将您的代码放在 Ispostback 中。

protected override void CreateChildControls()         
{                      
 if(!ispostback){
 assignedItemsField = new HiddenField();     
 assignedItemsField.ID = "HiddenAssignedItems";
 assignedItemsField.EnableViewState = true;          
 unassignedItemsField = new HiddenField();           
 unassignedItemsField.ID = "HiddenUnassignedItems"; 
 unassignedItemsField.EnableViewState = true;      
 Controls.Add(assignedItemsField);             
 Controls.Add(unassignedItemsField);          
 base.CreateChildControls();      
}
 }