c＃如何检查用户在文本框中输入的字符串是否为中文？

// Warning, this code only works for common Han ideographs inside the BMP. (Surrogate code points will need special care, and additional ranges within the BMP contain rare, historic, and uncommon characters.)
const double hannessThreshold = 0.25d;
const char lowestHanCodepoint = \'\\u4E00\';
const char highestHanCodepoint = \'\\u9FFF\';
string text = myTextBox.Text;
int hanCharacterCount = 0;
foreach (char c in text)
    if (lowestHanCodepoint <= c && c <= highestHanCodepoint)
        hanCharacterCount++;
double hannessScore = (double)hanCharacterCount / text.Length;
if (hannessScore >= hannessThreshold)
    MessageBox.Show(\"You are typing in Chinese, Japanese, or Korean!\");