SharePoint : Add group of users to the user collection programmatically
The sample code as follows.
SPWeb web = new SPSite("Site URL").OpenWeb();
SPUserInfo[] userInfo = new SPUserInfo[1];
userInfo[0].Email = "email@microsoft.com";
userInfo[0].LoginName = @"domain\username";
userInfo[0].Name = "username";
userInfo[0].Notes = "Test";
web.Roles["Reader"].Users.AddCollection(userInfo);
