主题：判断与添空值

文本框输入问题

对于字符列

Dim a As String
IIF(bh.Text Is Nothing ," " ,a = bh.Text)没问题

但对于

Dim d As Double
IIF(yz.Text Is Nothing," ",d = yz.Text)

和

Dim q As Integer
IIF(nx.Text Is Nothing ," " ,q = nx.Text)

和

Dim o As Date
IIF(rz.Text Is Nothing ," " ,o = rz.Text)

都会报错，为什么