Urmatoarea situatie - System.NullReferenceException: Object reference not set to an instance of an object. :
Visual Studio 2005 ASP.Net urmatorul cod:
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
cs.Open()
sqlfltr = "select * from complet"
da = New SqlDataAdapter(sqlfltr, cs)
da.Fill(ds, sqlfltr)
dv = New DataView(ds.Tables(sqlfltr))
lstcomplete.DataSource = dv
lstcomplete.DataValueField = "nume"
lstcomplete.DataTextField = "nume"
lstcomplete.DataBind()
End Sub

Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
txtcomplet.Text = lstcomplete.SelectedItem.Value
End Sub

Se populeza cu datele din baza apoi da urmatoarea eroare:
Server Error in '/test' Application.
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Object reference not set to an instance of an object.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error:
Line 22:
Line 23: Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
Line 24: txtcomplet.Text = lstcomplete.SelectedItem.Value
Line 25: End Sub
Line 26:
Source File: C:\Inetpub\wwwroot\test\Default.aspx.vb Line: 24

Stack Trace:


[NullReferenceException: Object reference not set to an instance of an object.]
_Default.Button1_Click(Object sender, EventArgs e) in C:\Inetpub\wwwroot\test\Default.aspx.vb:24
System.Web.UI.WebControls.Button.OnClick(EventArgs e) +78
System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +100
System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +10
System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +13
System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +36
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2863




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Version Information: Microsoft .NET Framework Version:2.0.50727.3603; ASP.NET Version:2.0.50727.3082

Multumesc Anticipat ma doare capul de cateva zile si nu-i dau de cap.

P.S. Incepator in ale programatului

1. Trebuia sa pui if(Not Ispostback) in Page_load , altfel ti se incarca combo-ul de fiecare data

2. Daca nu ai nimic in lstcomplete , ce te faci ? ( sa zicem ca nu ai nimic in tabela complet)

if not (lstComplete.SelectedItem is nothing) then
txtcomplet.Text = lstcomplete.SelectedItem.Value
else
' ce pui acolo ?

---

Ignat Andrei
http://serviciipeweb.ro/iafblog

OK - multumesc mult (Incepator). Am pus conditia (Not IspostBAck) si functioneaza, insa daca selectez prima linie cu indexul i=0 nu se intampla nimic ca si cum nu as fi selectat nimic.

pai poti pune autopostback la true - ca sa faca postback

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Ignat Andrei
http://serviciipeweb.ro/iafblog

Am pus autopostback si aceiasi problema, nu pot selecta primul ITEM, index i=0. Multumesc pentru ajutor, in rest functioneza.
Daca populez LisBoxul - cu wizardul pus la bataie de VS se intampla acelasi lucru, item i=0 nu il pot selecta. Banuiesc ca este ceva de la mine.

Pai... habar nu am ce intelegi tu prin "nu pot selecta"....

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Ignat Andrei
http://serviciipeweb.ro/iafblog

scuze, m-am exprimat gresit

selectez primul item din lstComplete i=0 si
cand apelez
Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
txtcomplet.Text = lstcomplete.SelectedItem.Value
End Sub

rezulta
txtcomplet.Text nu afiseaza nimic ca si cum nu as fi selectat nimic, daca selectez al doilea sau urmatoarele totul este ok.

ce este in codul html(nu aspx!) la lstcomplete ?

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Ignat Andrei
http://serviciipeweb.ro/iafblog

td style="width: 151px" rowspan="3"
asp:Label ID="lblComplete" runat="server" Text="Lista complete"/asp:Label>
asp:ListBox ID="lstComplete" runat="server" Height="317px" Width="176px"/asp:ListBox /td
td style="width: 49px"


respectivul ListBox este pus intr-o celula a unui tabel daca conteaza asta

tocmai ti-am spus in html, nu in aspx ...
Ruleaza pagina in IE/FF  , da-i View=> Source si cauta lstComplete

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Ignat Andrei
http://serviciipeweb.ro/iafblog

multumesc mult pentru ajutor, problema era de la mine. Am pus o conditie (inainte sa pun If NOT ISpostBack) in cazul in care SelectedIndex = 0 sa-mi afiseze un mesaj ca sa pot vedea ce valoare are indexul, dupa ce m-ai ajuta am uitat sa scot acea conditie. Acum totul este OK. Multumesc inca o data