这是程序中一个按纽中的代码，请高手帮助分析一下：
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        SqlCmdGR.Connection = SqlConnGR
        SqlCmdGR.CommandText = "SELECT DISTINCT XQ_Name FROM DangAn"

        Dim strTemp As String
        Dim reXQName As SqlDataReader

        SqlConnGR.Open()
        reXQName = SqlCmdGR.ExecuteReader()
        While reXQName.Read
            If reXQName.GetString(0) Then
                strTemp = reXQName.GetString(0).Trim & vbCrLf '由于SQL2000库中的段XQ_Name可以用空，故reXQName.GetString(0)的值为NULL时程序出错，怎样判断reXQName.GetString(0)是否为空，为空则跳过
                ListBoxXQ.Items.Add(strTemp)
            End If
        End While
        reXQName.Close()
        SqlConnGR.Close()

    End Sub