How to remove ScriptManager from SharePoint Page via C#

Question

I am trying to remove the Scriptmanager from a SharePoint page in code so I can swap it with the Ajax toolkit. However, when I use the following code I get:

Only one instance of a ScriptManager can be added to the page

The code errors on the Add statement. This has to be done via code as access to modify the master page source is not an option.

The code from my webpart that needs to replace the scriptmanager:

protected void GroupCalenderSourceControl_Init(object sender, EventArgs e)
    {
        //throw new NotImplementedException();
        ScriptManager sm = ScriptManager.GetCurrent(Page);

        if (sm == null)
        {
            Page.Controls.Add(new AjaxControlToolkit.ToolkitScriptManager());
        }
        else
        {
            if (!(sm is AjaxControlToolkit.ToolkitScriptManager))
            {
                Page.Controls.Remove(Page.FindControl(sm.ID));
                Page.Master.Controls.Remove(Page.FindControl(sm.ID));
                sm = null;
                Page.Controls.Add(new AjaxControlToolkit.ToolkitScriptManager());
            }
        }
    }

Answer 1

The main problem is that the page needs to complete the post-back to fully unregister the original script manager. Doing it in the same code block isn't going to work too well.

However, having read around this subject it seems AJAX Control Toolkit controls work perfectly fine with the standard ASP.NET ScriptManager. Can you not stick with that instead?

Whilst ToolkitScriptManager is meant to improve some of the ScriptManager's behaviors in particular how it renders out behavior JS scripts ScriptManager will execute its requests as fast as ToolkitScriptManager

Source: http://blog.turlov.com/2008/05/scriptmanager-vs-toolkitscriptmanager.html

Answer 2

Try with this code

  foreach (Control ctr in Page.Form.Controls)
        {
            if (ctr.GetType() == typeof(System.Web.UI.ScriptManager))
            {
                Page.Form.Controls.Remove(ctr);
                break;
            }
        }
     if (ScriptManager.GetCurrent(this.Page) == null)
         {
             ScriptManager scriptManager = new ScriptManager();
             scriptManager .ID = "scriptManager" + RandomNo;
             Page.Form.Controls.AddAt(0, scriptManager );
         }