动态加载 web 用户控件时的问题

Question

网页用户控件：FilterLabel

<span style=" display:block; float:left; margin:5px; padding: 5px; border: 1px inset #000000; font-family: Tahoma; font-size: small;">
<asp:Label ID="lblFilterDisplay" runat="server" Text="Product/Service: This is a testing"></asp:Label>
&nbsp;
<asp:ImageButton ID="btnRemove" runat="server" ImageUrl="~/Images/remove.png" OnClick="btnRemove_Click" />

以及该网页用户控件的后台代码部分：

public event EventHandler RemoveClick;
......
public void btnRemove_Click(object sender, EventArgs e)
{
    if (RemoveClick != null)
        RemoveClick(this, EventArgs.Empty);
}

接下来，网络用户控件“FilterLabel”将用于另一个网络用户控件“FilterList”：

<%@ Register TagPrefix="uc" TagName="FilterLabel" Src="~/Controls/FilterLabel.ascx" %>
<asp:Panel ID="FilterList" runat="server" Width="100%" GroupingText="Filter List" CssClass="filterList">
</asp:Panel>

而这个网页用户控件背后的代码部分是：

protected override void OnInit(EventArgs e)
{
    if (IsPostBack)
    {
        BindFilters();
    }

}

public void BindFilters()
{
    List<FilterLabel> filters = Filters;
    foreach (FilterLabel filter in filters)
    {
        FilterList.Controls.Add(filter);
    }
}

public List<FilterLabel> Filters
{
    get
    {
        List<FilterLabel> filters = Session["Filters"] as List<FilterLabel>;
        if (filters == null)
        {
            filters = new List<FilterLabel>();
        }
        return filters;
    }
}

public void AddFilter(string filterName, string filterContent, string filterValue = null)
{
    FilterLabel filter = LoadControl("~/Controls/FilterLabel.ascx") as FilterLabel;
    filter.ID = "Filter";
    filter.FilterContent = filterContent;
    filter.FilterName = filterName;
    filter.Value = filterValue;
    filter.RemoveClick += new EventHandler(RemoveFilter);
    List<FilterLabel> filters = Filters;
    filters.Add(filter);
    Session["Filters"] = filters;
    BindFilters();
}

private void RemoveFilter(object sender, EventArgs e)
{
    //some handling codes
}

所以现在的问题是当我单击图像按钮“btnRemove”时，btnRemove_Click 事件没有被激活。

Answer 1

您应该尝试使用气泡事件。使用您的解决方案，您需要在每次回发时为现有过滤器的每个用户控件重新绑定事件处理程序

public int FilterCount 
{
    get{
        if(ViewState["filter_count"] == 0){
            FilterCount = 0;
        }
        return (int)ViewState["filter_count"];
    }
    set{
        ViewState["filter_count"] = value;
    }
}

protected void RecreateFilterControlls()
{
    for(int i =0; i < FilterCount; i++){
        FilterLabel filter = LoadControl("~/Controls/FilterLabel.ascx") as FilterLabel;
        FilterList.Controls.Add(filter);
        filter.RemoveClick += new EventHandler(RemoveFilter);
    }
}


protected override void OnInit(EventArgs e)
{
    if (IsPostBack)
    {
        RecreateFilterControlls();
    }

}
// this is for button which will add new FilterLabel UserControl
protected void AddNewFilter_Click(object sender, EventArgs e)
{
    // just create filter
    AddFilter(<FilterNameTextBox|combobox>, <FilterContentTextBox>, <filterValue>);
}


public void AddFilter(string filterName, string filterContent, string filterValue = null)
{
    FilterLabel filter = LoadControl("~/Controls/FilterLabel.ascx") as FilterLabel;
    filter.ID = "Filter";
    filter.FilterContent = filterContent;
    filter.FilterName = filterName;
    filter.Value = filterValue;
    filter.RemoveClick += new EventHandler(RemoveFilter);
    // increament filter count
    FilterCount++;

}

private void RemoveFilter(object sender, EventArgs e)
{
    //some handling codes
    //remove control which caused this event
    FilterList.Controls.Remove(sender); // or you will need to ask for IndexOf(sender);
    FilterCount--;
}

其余的将由 ViewState 自己处理，因此您不需要将数据绑定回 FilterLabel 回来