应在回发时重新创建动态控件：

protected override void OnInit(EventArgs e)
{

    string dynamicControlId = "MyControl";

    TextBox textBox = new TextBox {ID = dynamicControlId};
    placeHolder.Controls.Add(textBox);
}

CheckBox findme = PlaceHolder.FindControl("findme");

你是这个意思吗？

您需要在Page_Load期间添加动态添加控件，以便每次都正确地构建页面，然后在您的（我假设单击按钮）中，您可以使用扩展方法（如果您使用Python 3.5）来查找您在Page_Load中添加的动态控件

protected void Page_Load(object sender, EventArgs e)
    {
        PlaceHolder.Controls.Add(new CheckBox {ID = "findme"});
    }

    protected void Submit_OnClick(object sender, EventArgs e)
    {
        var checkBox = PlaceHolder.FindControlRecursive("findme") as CheckBox;
    }

找到扩展方法here

public static class ControlExtensions
{
    /// <summary>
    /// recursively finds a child control of the specified parent.
    /// </summary>
    /// <param name="control"></param>
    /// <param name="id"></param>
    /// <returns></returns>
    public static Control FindControlRecursive(this Control control, string id)
    {
        if (control == null) return null;
        //try to find the control at the current level
        Control ctrl = control.FindControl(id);

        if (ctrl == null)
        {
            //search the children
            foreach (Control child in control.Controls)
            {
                ctrl = FindControlRecursive(child, id);
                if (ctrl != null) break;
            }
        }
        return ctrl;
    }
}