Programmatically how to assign user to SharePoint group

Assign a user to group:

In this example, i wanna show how to create group, assign role to the group and assign a user to the group.

            using (SPSite site = new SPSite("http://UKREDDY:6969/"))
            {
                using (SPWeb web = site.OpenWeb())
                {
                    web.AllowUnsafeUpdates = true;
                    web.SiteGroups.Add("UdayGroup", web.CurrentUser, web.CurrentUser, "This is Test Group for adding users to group.");
                    SPGroup group = web.SiteGroups["UdayGroup"];
                    SPRoleDefinition roleDefinition = web.RoleDefinitions.GetByType(SPRoleType.Contributor);
                    SPRoleAssignment roleAssigment = new SPRoleAssignment(group);
                    roleAssigment.RoleDefinitionBindings.Add(roleDefinition);
                    web.RoleAssignments.Add(roleAssigment);
                    web.Update();
                    SPUser spUser = web.EnsureUser("ukreddysykam\\urkeddy");
                    group.Users.Add(spUser.LoginName, spUser.Email, spUser.Name, spUser.Notes);
                    web.AllowUnsafeUpdates = false;
                }
            }