Why is Yongzheng called Ling Xuan?

According to the relevant information of the TV series "The Queen of the Palace", Ling Xuan is a character in the original TV series. Later, director Zheng Xiaolong adapted the TV series, and the story was adapted to the Yongzheng period of the Qing Dynasty. The hero is Yongzheng, and his name is Ling Xuan. Yongzheng emperor, the fourth son of the fifth emperor Kangxi of the Qing Dynasty, was born in Yonghe Palace in the Forbidden City in Beijing.