Francesco Geri

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Problemi con DropDownList e XMLDataSource creati dinamicamente

Oggi ho avuto dei problemi a collegare due dropdownlist a fonti dati basate su XML.
Andiamo per ordine.
Ho creato un'applicazione con 2 DropDownList, ciascuna collegata ad un XmlDataSource che si legge un suo file XML:
 
   1: <html xmlns="http://www.w3.org/1999/xhtml">
   2: <head runat="server">
   3:     <title>Untitled Page</title>
   4: </head>
   5: <body>
   6:     <form id="form1" runat="server">
   7:         <div>
   8:             <asp:DropDownList ID="DropDownList1" runat="server" Width="344px" DataSourceID="XmlDataSource1"
   9:                 DataTextField="key" DataValueField="key">
  10:             </asp:DropDownList><asp:XmlDataSource ID="XmlDataSource1" runat="server" DataFile="~/XML1.xml"
  11:                 XPath="//values/value"></asp:XmlDataSource>
  12:             <br />
  13:             <br />
  14:             <br />
  15:             <asp:DropDownList ID="DropDownList2" runat="server" DataSourceID="XmlDataSource2"
  16:                 DataTextField="key" DataValueField="key" Width="336px">
  17:             </asp:DropDownList><asp:XmlDataSource ID="XmlDataSource2" runat="server" DataFile="~/XML2.xml"
  18:                 XPath="//values/value"></asp:XmlDataSource>
  19:         </div>
  20:     </form>
  21: </body>
  22: </html>

I 2 file XML1.xml e XML2.xml contengono rispettivamente:

   1: <values>
   2:     <value key="Valore 1"/>
   3:     <value key="Valore 2"/>
   4:     <value key="Valore 3"/>
   5:     <value key="Valore 4"/>
   6: </values>

e

   1: <values>
   2:     <value key="Test 1"/>
   3:     <value key="Test 2"/>
   4:     <value key="Test 3"/>
   5: </values>

Tutto funziona perfettamente e le 2 DropDownList vengono popolate l'una con i valori "Valore 1", "Valore 2", etc e l'altra con i valori "Test 1", etc.

 

Ora voglio fare un passo avanti, voglio popolare le DropDownList a runtime, con delle XmlDataSource che creo al volo.

Ecco come diventa la mia form:

   1: <html xmlns="http://www.w3.org/1999/xhtml" >
   2: <head runat="server">
   3:     <title>Untitled Page</title>
   4: </head>
   5: <body>
   6:     <form id="form1" runat="server">
   7:             <asp:DropDownList ID="DropDownList1" style="width: 416px"  runat=server />
   8:             <br />
   9:             <br />
  10:             <br />
  11:             <asp:DropDownList ID="DropDownList2" style="width: 472px" runat=server />
  12:     </form>
  13: </body>
  14: </html>

Metto il contenuto dei 2 file XML in 2 risorse del progetto, chiamandole XML1 e XML2, e nel code behind della form scrivo quanto segue:

   1: Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
   2:     Dim ds As New XmlDataSource()
   3:     ds.XPath = "//values/value"
   4:     ds.Data = My.Resources.XML1
   5:     Me.DropDownList1.DataSource = ds
   6:     Me.DropDownList1.DataValueField = "key"
   7:     Me.DropDownList1.DataTextField = "key"
   8:     Me.DropDownList1.DataBind()
   9:     ds.Dispose()
  10:     ds = Nothing
  11:  
  12:     ds = New XmlDataSource()
  13:     ds.XPath = "//values/value"
  14:     ds.Data = My.Resources.XML2
  15:     Me.DropDownList2.DataSource = ds
  16:     Me.DropDownList2.DataValueField = "key"
  17:     Me.DropDownList2.DataTextField = "key"
  18:     Me.DropDownList2.DataBind()
  19:     ds.Dispose()
  20:     ds = Nothing
  21: End Sub

 

Lancio la mia pagina e mi ritrovo una brutta sorpresa.... entrambe le DropDownList contengono gli stessi dati!!!!

Mi arrovello per un po' e con l'aiuto del collega Alessio scopro (cioè è lui che lo scopre...) se cambio i nomi dei tag dell'XML2 (in modo che non siano gli stessi usati in XML1) succede qualcosa... succede che la seconda DropDownList non carica più niente....

 

Ci rinuncio e passo ad un workaround in perfetto stile volpe con l'uva... 

   1: Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
   2:  
   3:     Dim xmlDoc1 As New XmlDocument
   4:     Dim dtValues1 As New DataTable("values")
   5:     dtValues1.Columns.Add(New DataColumn("key", Type.GetType("System.String")))
   6:     xmlDoc1.LoadXml(My.Resources.XML1)
   7:     ' Cerca i nodi relativi ai valori
   8:     Dim xmlNodes1 As XmlNodeList = xmlDoc1.SelectNodes("//values/value")
   9:     If Not xmlNodes1 Is Nothing Then
  10:         For i As Integer = 0 To xmlNodes1.Count - 1
  11:             dtValues1.Rows.Add(New String() {xmlNodes1(i).Attributes("key").Value})
  12:         Next
  13:     End If
  14:     Dim dsValues1 As New DataSet
  15:     dsValues1.Tables.Add(dtValues1)
  16:     Me.DropDownList1.DataSource = dsValues1
  17:     Me.DropDownList1.DataMember = "values"
  18:     Me.DropDownList1.DataValueField = "key"
  19:     Me.DropDownList1.DataTextField = "key"
  20:     Me.DropDownList1.DataBind()
  21:     dsValues1.Dispose()
  22:     dsValues1 = Nothing
  23:  
  24:     Dim xmlDoc2 As New XmlDocument
  25:     Dim dtValues2 As New DataTable("values")
  26:     dtValues2.Columns.Add(New DataColumn("key", Type.GetType("System.String")))
  27:     xmlDoc2.LoadXml(My.Resources.XML2)
  28:     ' Cerca i nodi relativi ai valori
  29:     Dim xmlNodes2 As XmlNodeList = xmlDoc2.SelectNodes("//values/value")
  30:     If Not xmlNodes2 Is Nothing Then
  31:         For i As Integer = 0 To xmlNodes2.Count - 2
  32:             dtValues2.Rows.Add(New String() {xmlNodes2(i).Attributes("key").Value})
  33:         Next
  34:     End If
  35:     Dim dsValues2 As New DataSet
  36:     dsValues2.Tables.Add(dtValues2)
  37:     Me.DropDownList2.DataSource = dsValues2
  38:     Me.DropDownList2.DataMember = "values"
  39:     Me.DropDownList2.DataValueField = "key"
  40:     Me.DropDownList2.DataTextField = "key"
  41:     Me.DropDownList2.DataBind()
  42:     dsValues2.Dispose()
  43:     dsValues2 = Nothing
  44:  
  45: End Sub

Print | posted on giovedì 25 settembre 2008 06:51 | Filed Under [ ASP.NET 2.0 Tips ]

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