Asp.net 在初始化之后、页面加载之前运行

由于

ddlPlant\u SelectedIndexChanged

导致回发后，我需要设置set

HttpContext.Current.Session（“PlantNumber”）

。这需要在Site.Master中加载ddlPlant之后，但在Default.aspx中的代码需要该值之前发生

Public Class SiteMaster Inherits MasterPage
    Protected Sub Page_Init(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Init
        If (Not Page.IsPostBack) Then
            ddlPlant.DataSource = myDataSource
            ddlPlant.DataBind()
            ddlPlant.SelectedValue = "1"
        End If

        HttpContext.Current.Session("PlantNumber") = ddlPlant.SelectedValue  
    End Sub

    Protected Sub ddlPlant_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs) Handles ddlPlant.SelectedIndexChanged
    End Sub
End Class


Public Class _Default Inherits Page
    Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
        Dim units As New List(Of EquipmentModel)
        For Each unit As EquipmentModel In getUnits.Out.Results
            If (CStr(unit.Plant_ID) = HttpContext.Current.Session("PlantNumber")) Then
                units.Add(unit)
            End If
        Next

        gvEquipmentUnit.DataSource = units.OrderBy(Function(n) n.Equipment_ID)
        gvEquipmentUnit.DataBind()
End Sub

对于上面的代码，当回发后设置

会话（“PlantNumber”）

时，ddlPlant.SelectedIndex=Nothing，ddlPlant.SelectedValue为空字符串

---

我已尝试将

会话（“PlantNumber”）=ddlPlant.SelectedValue

行移动到Site.Master's Page\u加载，但在默认情况下需要加载后运行。aspx.vb

我查看了PreLoad，但显然它对Master Page不起作用

最终，我决定不使用会话变量，而是直接从任何需要加载该值的页面（几乎所有页面）调用控件：

---

对不起，这个坏建议。

DirectCast(Master.FindControl("ddlPlant"), DropDownList).SelectedValue