的ObjectContext的實例已被設置，並且不再能夠用於添加額外下拉列表

Question

當我有以下代碼需要連接的操作：

If Page.IsPostBack = False Then 
     ' If prospect is coming from unique url 
     Dim prospect_url As String = Page.RouteData.Values("value") 
     ' Save prospect_url into session variable 
     Session("prospect_url") = prospect_url 
     Using dbContext As IRFEntities = New IRFEntities 
      ' Prepopulate the states dropdown. 
      Dim getStates = (From p In dbContext.IRF_States _ 
          Order By p.name _ 
          Select p) 
      ddlState.DataSource = getStates 
      ddlState.DataTextField = "name" 
      ddlState.DataValueField = "id" 
      ddlState.DataBind() 
      ' Grab info. about prospect based on unique url. 
      Dim getProspect = (From p In dbContext.IRF_Prospects _ 
           Where p.url = prospect_url _ 
           Select p).FirstOrDefault 
      ' If they have a record... 
      If getProspect IsNot Nothing Then 
       'If IsDBNull(getProspect.user_id) Then 
       If getProspect.user_id Is Nothing Then 
        ' Prepopulate the form with their information. 
        ' These must have a value, so we need to make sure that no column is null in the database. 
        txtFirst.Text = getProspect.first_name 
        txtLast.Text = getProspect.last_name 
        txtAddress.Text = getProspect.address 
        txtCity.Text = getProspect.city 
        ddlState.SelectedValue = getProspect.state 
        txtZip.Text = getProspect.zip 
        txtPhone.Text = getProspect.phone 
        txtEmail.Text = getProspect.email_address 
        txtYearEnrolling.Text = getProspect.enrolling_in 
       Else 
        ' Redirect them to login. 
        Response.Redirect("login.aspx") 
       End If 
      End If 
     End Using 
    End If 

我然後直接加入下面ddlState.DataBind（）在以下：

' Prepopulate the programs dropdown. 
      Dim getPrograms = (From p In dbContext.IRF_Program _ 
           Order By p.name _ 
          Select p) 
      ddlProgram.DataSource = getPrograms 
      ddlProgram.DataTextField = "name" 
      ddlProgram.DataValueField = "id" 
      ddlState.DataBind() 

現在我得到的錯誤：

The ObjectContext instance has been disposed and can no longer be used for operations that require a connection

如果我註釋掉櫻雪有用的代碼，代碼有效。爲什麼此代碼導致問題？

Answer 1

你已經失去了這個對象：

dbContext

也就是說已經處置和清理此對象的資源（包括連接操作）。如果您需要綁定另一個下拉列表，您可以重新創建該對象。

Dim dbContext as IRFEntities=Nothing 

Using dbContext= New IRFEntities 
    //perform first databind 
End Using 

Using dbContext = New IRFEntities 
    //code to perform second databind 
End Using