Additional code required when developing custom visual web part for anonymous access?

Question

I have a simple custom web part with three drop downs that reads from three different list. When the user tries to access this page they get prompted for password, if they don't enter any credentials they get a 401 error.

I have enabled anonymous access both in central admin and on the site itself, users can browse to the site and view it without getting prompted for password. I have made sure that anonymous user have "view" access to the lists in questions but they still can't view any page with a custom web part.

So is it a SharePoint setting or do I have to add something in my web part projects?

Thanks in advance.

Edit:

I call this method in page load and still get the same error

private void LoadImageGallery()
{
    SPSecurity.RunWithElevatedPrivileges(delegate()
    {
    SPSite oSiteCollection = SPContext.Current.Site;
    SPWebCollection collWebsites = oSiteCollection.AllWebs;
        DataTable dt = new DataTable();
        for (int i = 0; i < collWebsites.Count; i++)
        {
            using (SPWeb oWebsite = collWebsites[i])
            {
                if (oWebsite.Title == "People")
                {
                    SPList peopleList = oWebsite.Lists["Pages"];
                    if (peopleList != null)
                    {
                        SPListItemCollection collListItems = peopleList.Items;
                        dt = collListItems.GetDataTable();
                        // Include Surname to omit default/search page
                        dt = collListItems.GetDataTable();
                        rptImageGallery.DataSource = dt;
                        rptImageGallery.DataBind();
                    }
                }
            }
        }
    });
}

I also tried with

SPSite oSiteCollection = SPContext.Current.Site;
SPWebCollection collWebsites = oSiteCollection.AllWebs;

above runwithelevated..

I set system\sharepoint to have full control in the entire site

Answer 1

The custom page needs to meet two requirements so that the anonymous users can access it:

1. it needs to inherit from the class UnsecuredLayoutsPageBase,
2. the property AllowAnonymousAccess needs to be overridden to return true.

Answer 2

For anonymous access, you have to modified your code for access List to bind drop down list as below. Add you code in SPSecurity.RunWithElevatedPrivileges Delegate method.

       SPSecurity.RunWithElevatedPrivileges(delegate() {
          using (SPSite site = new SPSite(web.Site.ID))
          {            
             //ADD YOUR WEB PART Code HERE     
          }
       });

Important: You must create SharePoint Objects in this Delegate otherwise code will not run with Admin access.