Checking permissions of a user with a site collection - sharepoint

Question

I want to check whether a user has permissions to a site collection. But i dono how to use SPSite.DoesUserHavePermissions().
What is SPReusableAcl? How can i get it for checking the permissions of the user?

Answer 1

Doesn't the MSDN article (SPWeb.DoesUserHavePermissions Method (String, SPBasePermissions)) help you? The example code can be used to check whether the user has access to a site collection:
using System;
using Microsoft.SharePoint;
namespace Test
{
class Program
{
static void Main(string[] args)
{
using (SPSite site = new SPSite("http://localhost"))
{
using (SPWeb web = site.OpenWeb())
{
// Make sure the current user can enumerate permissions.
if (web.DoesUserHavePermissions(SPBasePermissions.EnumeratePermissions))
{
// Specify the permission to check.
SPBasePermissions permissionToCheck = SPBasePermissions.ManageLists;
Console.WriteLine("The following users have {0} permission:", permissionToCheck);
// Check the permissions of users who are explicitly assigned permissions.
SPUserCollection users = web.Users;
foreach (SPUser user in users)
{
string login = user.LoginName;
if (web.DoesUserHavePermissions(login, permissionToCheck))
{
Console.WriteLine(login);
}
}
}
}
}
Console.ReadLine();
}
}
}
In the sample code above you would just have to change your Site URL and the Variable permissionToCheck. SPBasePermissions has a lot of possible permissions to check against, you can see the enumeration here (SPBasePermissions Enumeration).
Actually there are a lot of tutorials on how to check some user's permissions and you are not limited to DoesUserHavePermissions, see the following Google Search.

Answer 2

As usual, the MSDN examples provide nice textbook examples that do not always apply to real-life scenarios.
In the context of an application page running on SharePoint 2010, from what i understand this code needs to be wrapped in a call to RunWithElevatedPrivileges and even then, as my comment implies, it seems there is an implied catch-22 in the requirements. This works for me (the LoginName is just the FBA username or "domain\user" for AD user for the site - in our case an e-mail address is used):
SPSecurity.RunWithElevatedPrivileges(delegate()
{
using (SPSite elevatedSite = new SPSite(siteCollectionUrl))
{
foreach (SPSite siteCollection in elevatedSite.WebApplication.Sites)
{
using (SPWeb elevatedWeb = siteCollection.OpenWeb())
{
bool allowUnsafeUpdates = elevatedWeb.AllowUnsafeUpdates;
bool originalCatchValue = SPSecurity.CatchAccessDeniedException;
SPSecurity.CatchAccessDeniedException = false;
try
{
elevatedWeb.AllowUnsafeUpdates = true;
// You can't verify permissions if the user does not exist and you
// can't ensure the user if the user does not have access so we
// are stuck with a try-catch
SPUser innerUser = elevatedWeb.EnsureUser(loginName);
if (null != innerUser)
{
string splogin = innerUser.LoginName;
if (!string.IsNullOrEmpty(splogin) && elevatedWeb.DoesUserHavePermissions(splogin, SPBasePermissions.ViewPages))
{
// this user has permissions; any other login - particularly one that
// results in an UnauthorizedAccessException - does not
}
}
}
catch (UnauthorizedAccessException)
{
// handle exception
}
catch (Exception)
{
// do nothing
}
finally
{
elevatedWeb.AllowUnsafeUpdates = allowUnsafeUpdates;
// reset the flag
SPSecurity.CatchAccessDeniedException = originalCatchValue;
}
}
}
}
});

Answer 3

SPSite.DoesUserHavePermissions(SPReusableAcl, SPBasePermissions);