How to judge a character in C # as a kanji

A small point of knowledge, but also the interview was asked, so summarize:

Enter a character char str

1. Use ASCII code to judge, English is 0-127, Chinese character >127

if ((int) str>127)---> is kanji

2. Using the Unicode encoding range of Chinese characters, the Unicode encoding of Chinese characters is 4E00-9FBB

if (STR>=4E00&&STR<=9FBB)----> is Kanji

3. Judging with regular expressions

if (Regex.IsMatch (str. ToString (), @ "[\u4e00-\u9fbb]+$"))--->true, is the kanji

How to judge a character in C # as a kanji