Q:

Remove SharePoint User with Only Partial Login Name

I have a need to remove a user's permissions from a site collection. The issue is that I do not have the entire loginName. Each user is given a unique loginName (e.g. DOMAIN/012345678.cnd) The 'cnd' portion can change per user and the numeric portion is always unique. 
So what I want to do is pass in a variable where only the numeric portion is known and and then based on that, it removes the user. 
I have the following code:
using (SPWeb oWebsiteRoot = SPContext.Current.Site.RootWeb){
            SPGroupCollection collGroups = oWebsiteRoot.SiteGroups;
            SPUser oUser = oWebsiteRoot.SiteUsers[""];
        }

So there need to be some way to set the oUser to be loginName given only the numeric part. I can always get the domain easily enough. It is the last part after the number sequence I cannot get.

A:

It's not a clean solution but it's a start:
           SPWeb oWebsiteRoot = SPContext.Current.Site.RootWeb;

            SPGroupCollection collGroups = oWebsiteRoot.SiteGroups;
            foreach(SPGroup group in collGroups)
            {
                for(int i=group.Users.Count; i>=0;i--)
                {
                    SPUser user = group.Users[i];
                    if (listOfDecimalsToBeDeleted.Contains(getUserDecimalPart(user.LoginName)))
                    {
                        group.RemoveUser(user);
                    }
                }
            }

