ASP.NET dynamically adding UserControl to PlaceHol

问题:

In my ASP.Net page I have PlaceHolder and Button. When user click on this button, I add some UserControls from my Interface method getControl to the PlaceHolder. Code:

    protected void ActionBtn_Click(object sender, EventArgs e)
    {
        if (provider != null)
        {
            actualObject = (PlaceHolder)provider.getControl();
            PlaceHolder1.Controls.Add(actualObject);
        }
    }

Method getControl:

    public object getControl()
    {
        ph = new PlaceHolder();

        exportInbBtn = new Button();
        exportInbBtn.Text = "Export Inventury";
        exportInbBtn.Click += new EventHandler(myButton_ServerClick);
        ph.Controls.Add(exportInbBtn);
        exportInbBtn.ID = "exportInbBtn";

        return ph;
    }

Methods Page_Load and Page_Init in ASP page are empty. Problem is, when the user click at the button exportInbBtn (with text: "Export Inventury"), the click event myButton_ServerClick will not rise. Only web page refresh. I ready some answers, but I can´t figure how easily solve this problem.

回答1:

If you fire *myButton_ServerClick* event, postback is invoked and ASP.Net want to fire called event, but your control is not added to the page, that's why ASP.Net ignore this event.

After postback and before event to be fired, you must add your control again and after them, event will be invoked.

Update

Something like this

Page:

<asp:Button runat="server" ID="btnTest" Text="Add control" OnClick="btnTest_Click"/>
<asp:Label runat="server" ID="result"></asp:Label>
<asp:HiddenField runat="server" ID="controlLoaded"/>
<asp:PlaceHolder runat="server" ID="phTest"></asp:PlaceHolder>

Code behind:

    protected void Page_Load(object sender, EventArgs e)
    {
        if (controlLoaded.Value == "1")
        {
            AddControl();
        }
    }

    protected void btnTest_Click(object sender, EventArgs e)
    {
        AddControl();
    }

    protected void myButton_ServerClick(object sender, EventArgs e)
    {
        result.Text = "OK";
    }

    public object getControl()
    {
        var ph = new PlaceHolder();

        var exportInbBtn = new Button();
        exportInbBtn.Text = "Export Inventury";
        exportInbBtn.Click += new EventHandler(myButton_ServerClick);
        ph.Controls.Add(exportInbBtn);
        exportInbBtn.ID = "exportInbBtn";

        return ph;
    }

    private void AddControl()
    {
        var actualObject = (PlaceHolder)getControl();
        phTest.Controls.Add(actualObject);
        controlLoaded.Value = "1";
    }

回答2:

Please note that UserControls are added by the below method - // First create the instance of user control var control = Page.LoadControl("~/folder1/UserControl1.ascx")

// Now add this control to placeholder as - placeHolder1.Controls.Add(control);

I hope this helps.

回答3:

page.aspx

<asp:PlaceHolder ID="PlaceHolder1" runat="server" ></asp:PlaceHolder>

page.aspx.vb

Private Sub CreateControl()
    Dim vw As Control
    vw = CType(LoadControl("~/View01.ascx"), View01)
    vw.ID = "View_Dyn"
    PlaceHolder1.Controls.Clear()
    PlaceHolder1.Controls.Add(vw)
End Sub

Recreate it every postback

Private Sub Page_Init(sender As Object, e As System.EventArgs) Handles Me.Init
    CreateControl()
End Sub