解决方法
使用自定义基本控制器并从中继承：
Public Class CustomBaseController
Inherits System.Web.Mvc.Controller
Protected Overrides Function View(ByVal viewName As String,ByVal masterName As String,ByVal model As Object) As System.Web.Mvc.ViewResult
Return MyBase.View(viewName,Session("MasterPage"),model)
End Function
End Class
我在global.asax Session_Start中设置了Session变量：
Sub Session_Start(ByVal sender As Object,ByVal e As EventArgs)
//programming to figure out your session
Session("MasterPage")="MyMasterPage"
End Sub
