在自定义控件中事件不会触发

我试图创建一个简单的自定义控件,其中控件上有一个图像按钮和一个标签。

有人能告诉我是什么错误吗???

public override ControlCollection Controls
{
    get
    {
        EnsureChildControls();
        return base.Controls;
    }
}

protected override void RenderContents(HtmlTextWriter output)
{
    //CreateChildControls();
    AssociateValuesWithProperties();

    ibFirst.RenderControl(output);
    output.RenderEndTag();
}

protected override void CreateChildControls()
{
    Controls.Clear();

    // Set subcontrols behavior
    //adding the event handlers to the image buttons
    ibFirst.Click += new ImageClickEventHandler(ibFirst_Click);
}

private void AssociateValuesWithProperties()
{
    ibFirst.ImageUrl = FirstImageSrcNormal;
    ibFirst.AlternateText = FirstImageAltText;
    ibFirst.ToolTip = FirstImageAltText;
}

protected void ibNext_Click(object sender, ImageClickEventArgs e)
{
    this.CurrentPage++;
}

谢谢您。