if (checkString.Length == Encoding.Default.GetByteCount(checkString)) { return true; } else { return false; }

if (2 * checkString.Length == Encoding.Default.GetByteCount(checkString)) { return true; } else { return false; }

#region 全角半角转换         /// <summary>         /// 转全角的函数(SBC case)         /// </summary>         /// <param name="input">任意字符串</param>         /// <returns>全角字符串</returns>         ///<remarks>         ///全角空格为12288，半角空格为32         ///其他字符半角(33-126)与全角(65281-65374)的对应关系是：均相差65248         ///</remarks>         public  static string ToSBC(string input)         {             //半角转全角：             char[] c=input.ToCharArray();             for (int i = 0; i < c.Length; i++)             {                 if (c[i]==32)                 {                     c[i]=(char)12288;                     continue;                 }                 if (c[i]<127)                     c[i]=(char)(c[i]+65248);             }             return new string(c);         }         /// <summary> 转半角的函数(DBC case) </summary>         /// <param name="input">任意字符串</param>         /// <returns>半角字符串</returns>         ///<remarks>         ///全角空格为12288，半角空格为32         ///其他字符半角(33-126)与全角(65281-65374)的对应关系是：均相差65248         ///</remarks>         public static string ToDBC(string input)         {             char[] c=input.ToCharArray();             for (int i = 0; i < c.Length; i++)             {                 if (c[i]==12288)                 {                     c[i]= (char)32;                     continue;                 }                 if (c[i]>65280 && c[i]<65375)                     c[i]=(char)(c[i]-65248);             }             return new string(c);         }         #endregion