Question

我的页面顶部有两个按钮添加控制和清除控件。

单击“添加控件”将触发创建新Panel和新DropDownList的函数。

我为DropDownList指定了一个用于SelectedIndexChanged的Eventhandler。

我的想法是根据DropDownList中的选择，我将在该面板中创建另一个控件。

最终，该面板将包含一些我可以作为查询参数传递的字段。

我将面板存储在每个回发中重新创建的面板列表中。

我遇到的问题是我可以添加面板，删除面板并清除列表中的所有面板但是我似乎无法将SelectedIndexChanged触发器触发......它似乎永远不会被分配或者它每次回发都会丢失。

我已经用尽了谷歌的专业知识，我对自己感到非常沮丧。我愿意接受建议/修正。

谢谢。

List<Panel> persistControls = new List<Panel>();

protected override void OnInit(EventArgs e)
{
    if (Session["persistControls"] != null)
    {
        persistControls = (List<Panel>)Session["persistControls"];
        int count = 0;

        foreach (Panel dynamicControl in persistControls)
        {
            AddQuestionTypeDropDownList(count);
            dynamicControl.ID = "panel" + count;

            Button btnRemove = new Button();
            btnRemove.Click += new EventHandler(btnDelete_Click);
            btnRemove.Text = "Remove";
            btnRemove.CommandArgument = count.ToString();

            // Pushing to Placeholder
            myPlaceholder.Controls.Add(dynamicControl);
            myPlaceholder.Controls.Add(btnRemove);
            count++;
        }
    }
    base.OnInit(e);
}

// Calls three functions responsible for pulling from the Database and binding the Datagrid.
protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        GetClustersFromDatabase(userid);
        BindGrid();
        BindState();            
    }
}

private DropDownList AddQuestionTypeDropDownList(int count)
{
    DropDownList list = new DropDownList();

    list.ID = "list" + count;    
    list.Items.Add(new ListItem("--Select One--", ""));
    list.Items.Add(new ListItem("Title", "1"));
    list.Items.Add(new ListItem("Contact", "2"));
    list.Items.Add(new ListItem("Date Created", "3"));
    list.SelectedIndexChanged += new EventHandler(list_SelectedIndexChanged);
    list.AutoPostBack = true;

    return list;
}

private DropDownList AddQuestionTypeDropDownList()
{
    DropDownList list = new DropDownList();
    list.Items.Add(new ListItem("--Select One--", ""));
    list.Items.Add(new ListItem("Title", "1"));
    list.Items.Add(new ListItem("Contact", "2"));
    list.Items.Add(new ListItem("Date Created", "3"));
    list.SelectedIndexChanged += new EventHandler(list_SelectedIndexChanged);
    list.AutoPostBack = true;

    return list;
}

protected void btnAdd_Click(object sender, EventArgs e)
{
    try
    {
        Panel panelContainer = new Panel();
        panelContainer.ID = "panel" + persistControls.Count;

        panelContainer.Controls.Add(AddQuestionTypeDropDownList());

        Button btnRemove = new Button();
        btnRemove.Click += new EventHandler(btnDelete_Click);
        btnRemove.Text = "Remove";
        btnRemove.CommandArgument = persistControls.Count.ToString();

        myPlaceholder.Controls.Add(panelContainer); // Pushes the Panel to the page.
        persistControls.Add(panelContainer);// Adds our Panel to the Control list

        myPlaceholder.Controls.Add(btnRemove); // Pushes our Button to the page.
        Session["persistControls"] = persistControls; // put it in the session
    }
    catch
    {
        throw;
    }
}

private void list_SelectedIndexChanged(object sender, EventArgs e)
{
    //I have no code here but thats because I currently can't even get it to fire.
    try
    {

    }
    catch
    {
        throw;
    }
}

protected void btnClear_Click(object sender, EventArgs e)
{
    try
    {
        Session["persistControls"] = null;
        Response.Redirect(Request.Url.ToString());
    }
    catch
    {
        throw;
    }
}

protected void btnDelete_Click(object sender, EventArgs e)
{
    try
    {
        int deleteThisOne = int.Parse(((Button)sender).CommandArgument);
        persistControls.Remove(persistControls[deleteThisOne]);
        Session["persistControls"] = persistControls;          
        Response.Redirect(Request.Url.ToString());
    }
    catch
    {
        throw;
    }
}

Answer 1

我能够通过使用foreach遍历我的面板列表并使用嵌套的foreach迭代遍历该面板中的每个控件来解决问题。我检查控件的类型并在每次回发时修复eventhandler。

维护包含控件的Panel列表。丢失事件处理程序

1 个答案: