C# StringExtensions Class

Garkbit.StringExtensions.cs

/**
 * C# String Extensions
 * Copyright (c) 2011 marlun78
 * MIT License, https://gist.github.com/marlun78/bd0800cf5e8053ba9f83
 */
using System;
using System.Collections.Generic;

namespace Garkbit {
    public static class StringExtensions {

        public static bool IsNotNullOrEmpty(this string _this) {
            return !String.IsNullOrEmpty(_this);
        }


        public static string Repeat(this string _this, int count) {
            return Repeat(_this, count, String.Empty);
        }
        public static string Repeat(this string _this, int count, string separator) {
            if (count <= 0 || String.IsNullOrEmpty(_this)) {
                return String.Empty;
            }
            else {
                List<string> list = new List<string>();
                for (int i = 0; i < count; i++) {
                    list.Add(_this);
                }
                return String.Join(separator, list);
            }
        }


        public static bool ContainsAll(this string _this, params string[] values) {
            if (_this == null) {
                throw new NullReferenceException("String.ContainsAll() can not be called on a null value.");
            }
            for (int i = 0, l = values.Length; i < l; i++) {
                if (!_this.Contains(values[i])) {
                    return false;
                }
            }
            return true;
        }
        public static bool ContainsAny(this string _this, params string[] values) {
            if (_this == null) {
                throw new NullReferenceException("String.ContainsAny() can not be called on a null value.");
            }
            for (int i = 0, l = values.Length; i < l; i++) {
                if (_this.Contains(values[i])) {
                    return true;
                }
            }
            return false;
        }
    }
}