urldecode解码方法

输入为带有urldecode转码文本，输出正常文本。

//20130625 by zhangyl
private string ConvertToString(string input)
        {
            input = input.Replace("\\\"", "\"");
            input = input.Replace("\\/", "/");
            string result;
            if (!input.Contains("\\u"))
            {
                result = input;
            }
            else
            {
                StringBuilder stringBuilder = new StringBuilder();
                if (input.IndexOf("\\u") > )
                {
                    stringBuilder.Append(input.Substring(, input.IndexOf("\\u")));
                    input = input.Substring(input.IndexOf("\\u"));
                }
                if (!string.IsNullOrEmpty(input))
                {
                    string[] array = input.Split(new string[]
                    {
                        "\\u"
                    }, StringSplitOptions.RemoveEmptyEntries);
                    string[] array2 = array;
                    for (int i = ; i < array2.Length; i++)
                    {
                        string text = array2[i];
                        if (text.Length > )
                        {
                            string arg = text.Substring();
                            stringBuilder.Append((char)int.Parse(text.Substring(, ), NumberStyles.HexNumber) + arg);
                        }
                        else
                        {
                            if (text.Length == )
                            {
                                stringBuilder.Append((char)int.Parse(text, NumberStyles.HexNumber));
                            }
                            else
                            {
                                if (text.Length <  && text.Length > )
                                {
                                    stringBuilder.Append(text);
                                }
                            }
                        }
                    }
                }
                result = stringBuilder.ToString();
            }
            return result;
        }