Create Security Groups and Assign Permissions in SharePoint 2013

Here is a fun little helper for creating security groups with a permission assignment.
I use the word fun because I have been working with SharePoint too long and my brain now works in reverse.

/// <summary>

    /// Security Helper

    /// </summary>

    public class SecurityHelper

    {

        public static bool GroupExists(SPGroupCollection groups, string name)

        {

            if (String.IsNullOrEmpty(name) || (name.Length > 255) ||(groups == null) || (groups.Count == 0))

            {

                return false;

            }

            return groups.Cast<SPGroup>().FirstOrDefault(t => t.Name == name) != null;

        }

        /// <summary>

        /// Creates a group if it does not exist.  It will also assign a permission level to the group.

        /// </summary>

        /// <param name="web"></param>

        /// <param name="groupName"></param>

        /// <param name="permissionLevel"></param>

        /// <param name="description"></param>

        /// <param name="owner"></param>

        /// <returns>The Group</returns>

        public static SPMember CreateGroup(SPWeb web, string groupName, string permissionLevel, string description, SPMember owner = null)

        {

            string uniqueGroupName = String.Format("{0} - {1}", web.Name, groupName);

            if (!GroupExists(web.SiteGroups, uniqueGroupName))

            {

                var role = web.RoleDefinitions.Cast<SPRoleDefinition>().FirstOrDefault(t => t.Name == permissionLevel);

                if (role == null)

                {

                    throw new KeyNotFoundException(String.Format("The Security Permission level {0} does not exist at web {1}.", permissionLevel, web.Url));

                }

                if (owner == null)

                {

                    owner = web.CurrentUser;

                }

                web.SiteGroups.Add(uniqueGroupName, owner, null, description);

                SPGroup group = web.SiteGroups.GetByName(uniqueGroupName);

                var assignment = new SPRoleAssignment(@group);

                assignment.RoleDefinitionBindings.Add(role);

                web.RoleAssignments.Add(assignment);

            }

            return web.SiteGroups.GetByName(uniqueGroupName);

        }

    }