//控件代码
public partial class WebUserControl : System.Web.UI.UserControl
{
    public void TestMethod(string strID)
    {
        this.TextBox1.Text += " WebUserControl:" + strID;
        //其他相关操作
    }
}

//控件代码
public partial class WebUserControl2 : System.Web.UI.UserControl
{
    public void TestMethod(string strID)
    {
        this.TextBox1.Text += " WebUserControl2:" + strID;
        //根据传入参数进行其他相关操作
    }
}

//页面代码
public partial class Default1 : System.Web.UI.Page
{
    bool isShow = true;//是
    string strWebUserControls = "WebUserControl,WebUserControl2";
    protected void Page_Load(object sender, EventArgs e)
    {
        if (isShow)
        {
            string[] strUCs = strWebUserControls.Split(",".ToCharArray()[0]);
            for (int i = 0; i < strUCs.Length; i++)
            {
                string strUCName = strUCs[i].ToString();
                Control a = Page.LoadControl(strUCName+".ascx");
                a.ID = strUCName;
                this.Panel1.Controls.Add(a);
            }           
        } 
    }

    //页面按钮操作
    protected void Button1_Click(object sender, EventArgs e)
    {
        if (isShow)
        {
            string[] strUCs = strWebUserControls.Split(",".ToCharArray()[0]);
            for (int i = 0; i < strUCs.Length; i++)
            {
                string strUCName = strUCs[i].ToString();
                Type tc = this.Panel1.FindControl(strUCName).GetType();
                Control uc = this.Panel1.FindControl(strUCName);
                ////object o = System.Activator.CreateInstance(uc.GetType());
                System.Reflection.MethodInfo m = tc.GetMethod("TestMethod");
                object[] bjParas = new object[1];
                objParas[0] = "1";
                m.Invoke(uc, objParas);
                ////m.Invoke(a, null);
            }
        }
     }
}