为什么我的计数器变量不在这个vb.net代码示例中递增?

我有以下代码

Protected Sub btnAdd_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnAdd.Click

    Dim counter As Integer = 0
    Dim t As DataTable = DirectCast(Session("MyDataTable"), DataTable)
    Dim row1 As DataRow = t.NewRow()



    If (isUnique(t) And counter < 30) Then
        row1("ID") = counter + 1
        row1("univirsityID") = ddlUnivs.SelectedValue
        row1("majorID") = ddlMajors.SelectedValue
        row1("UniName") = ddlUnivs.SelectedItem.Text
        row1("MajorName") = ddlMajors.SelectedItem.Text
        t.Rows.Add(row1)
        Session("MyDataTable") = t
        GridView1.DataSource = t
        GridView1.DataBind()
        lblMsg.Text = "تم اضافة الرغبة"
        counter = counter + 1

    Else
        lblMsg.Text = "سبق لك ادخال الرغبة"
    End If

End Sub

问题是row1(“id”)没有更改,它一直为添加到数据表的所有行获取1的值。 谢谢你的帮助 事先谢谢。