如何判断值是否为空
代码如下:
STR = "select * from wlxx order by KML asc"
SQLCMD = New SqlCommand(STR, CONN)
CONN.Open()
SQLDR = SQLCMD.ExecuteReader
While SQLDR.Read
TextBox2.Text = SQLDR.GetString(1).ToString
TextBox3.Text = SQLDR.GetString(2).ToString
TextBox4.Text = SQLDR.GetDecimal(3).ToString
End While
CONN.Close()
因为表wlxx有的字段可以为空,我如何判断这个字段为空?