how to authenticate and login to sharepoint 2010 programmatically?

Question

when you in the SharePoint site anonymously, easily you can click on Login link and base on your authentication type either you prompted for credentials or will redirect to the login page(if FBA authentication). let's say i have the hardcode credentials in my code and want to do the same programmatically.

if i want to start from the beginning:
one of the sharepoint weakness is that you cant act for anonymous users, for instance you cant change or remove the permissions of a ListItem.
so i came to conclusion to use a user with the limited access as possible like Guest and when anonymous users in some specific page which is my Webpart in it, i use a hardcode credentials to login and redirect them to a page.
i know about impersonation and other stuff like it which is use in code behind world and it's not what i meant.
so the question is very simple, How Can I Do That?

Answer 1

I believe that this "weakness" it is not SharePoint's and it is not a weakness. Is actually ASP.NET Membership model or classic Windows Authentication. Then you could always to create code to impersonate other accounts for specific functions only, to avoid internet bots performing changes anonymously, e.g. anonymous comment on blog entries.

To change programatically the AnonymousPermissionsMask use this

using System.Web.Configuration;
using Microsoft.SharePoint;
using Microsoft.SharePoint.Administration;

using (SPSite specifiedSite = new SPSite("You specified web url"))
{
    using (SPWeb specifiedWeb = specifiedSite.OpenWeb())
    {
        // Enable anonymous access on web application
        SPUrlZone urlZone = SPUrlZone.Default;
        SPWebApplication specifiedWebApplication = specifiedSite.WebApplication;
        SPIisSettings iisSettings = specifiedWebApplication.IisSettings[urlZone];
        iisSettings.AuthenticationMode = AuthenticationMode.Windows;
        iisSettings.AllowAnonymous = true;
        specifiedWebApplication.Update();

        // Enable anonymous access on website
        specifiedWeb.AnonymousState = SPWeb.WebAnonymousState.On;
        specifiedWeb.AnonymousPermMask64 = SPBasePermissions.Open |
            SPBasePermissions.ViewPages | SPBasePermissions.ViewListItems;
        specifiedWeb.Update();

        // Enable anonymous acces on list
        SPList specifiedList = specifiedWeb.GetList("You specified list url");
        specifiedList.AnonymousPermMask64 = SPBasePermissions.ViewListItems |
            SPBasePermissions.AddListItems | SPBasePermissions.EditListItems |
            SPBasePermissions.DeleteListItems;
        specifiedList.Update();
    }
}

Answer 2

First, you can change the permissions of the anonymous user. The AnonymousPermMask64 property of the SPWeb/SPList object controls what permissions the anonymous user has.

Second, if you want to programmatically log in to a site, you can do so with the System.Web.HttpWebRequest class. You will need a host to run your code, such as a WinForm or console application. If you wish to have code run in the browser and log in, you may run into some difficulties. (Most browsers run with the security credentials of the logged-in user.)

Answer 3

As you have hard coded your credentials for anonymous user, assign this Guest User to Readers Group so that he has permission for all List Items.