System.NullReferenceException

How must i declare my variables to have this code work. I get
system.nullreferenceexception every time i click button to add data to
datatable
here below is my code :
Dim wykszt as System.Data.DataTable
Dim zatru as System.Data.DataTable
Private Sub Page_Load(s As Object, e As EventArgs)
if Not IsPostBack Then
make_d_tables()
End if
End Sub
sub make_d_tables()
wykszt = New System.Data.DataTable("wykszt")
wykszt.Columns.Add("od_data", GetType(date))
wykszt.Columns.Add("do_data", GetType(date))
wykszt.Columns.Add("nazwa_szkoly", GetType(String))
wykszt.Columns.Add("nazwa_tytulu", GetType(String))
zatru = New System.Data.DataTable("zatr")
zatru.Columns.Add("od_data", GetType(date))
zatru.Columns.Add("do_data", GetType(date))
zatru.Columns.Add("nazwa_prac", GetType(String))
zatru.Columns.Add("nazwa_stan", GetType(String))
End sub
Sub Button2_Click(sender As Object, e As EventArgs)
row = wykszt.NewRow
row("od_data")=TextBox27.Text + "-01"
row("do_data")=TextBox28.Text + "-01"
row("nazwa_szkoly")=TextBox29.Text
row("nazwa_tytulu")=TextBox30.Text
wykszt.Rows.Add(row)
row = wykszt.NewRow
Mxdatagrid1.datasource=wykszt
Mxdatagrid1.databind
End Sub
Thanks
PatYou have to recreate your tables every time. So take out the if statement
from page_load.
"ven" <venome_@.poczta.onet.pl> wrote in message
news:cif6p8$sf3$1@.news.onet.pl...
> How must i declare my variables to have this code work. I get
> system.nullreferenceexception every time i click button to add data to
> datatable
> here below is my code :
> Dim wykszt as System.Data.DataTable
> Dim zatru as System.Data.DataTable
> Private Sub Page_Load(s As Object, e As EventArgs)
> if Not IsPostBack Then
> make_d_tables()
> End if
> End Sub
> sub make_d_tables()
> wykszt = New System.Data.DataTable("wykszt")
> wykszt.Columns.Add("od_data", GetType(date))
> wykszt.Columns.Add("do_data", GetType(date))
> wykszt.Columns.Add("nazwa_szkoly", GetType(String))
> wykszt.Columns.Add("nazwa_tytulu", GetType(String))
> zatru = New System.Data.DataTable("zatr")
> zatru.Columns.Add("od_data", GetType(date))
> zatru.Columns.Add("do_data", GetType(date))
> zatru.Columns.Add("nazwa_prac", GetType(String))
> zatru.Columns.Add("nazwa_stan", GetType(String))
> End sub
> Sub Button2_Click(sender As Object, e As EventArgs)
> row = wykszt.NewRow
> row("od_data")=TextBox27.Text + "-01"
> row("do_data")=TextBox28.Text + "-01"
> row("nazwa_szkoly")=TextBox29.Text
> row("nazwa_tytulu")=TextBox30.Text
> wykszt.Rows.Add(row)
> row = wykszt.NewRow
> Mxdatagrid1.datasource=wykszt
> Mxdatagrid1.databind
> End Sub
>
> Thanks
> Pat
>
Which line is throwing the exception?
Does the error only happen on postback?
I hope this helps,
Steve C. Orr, MCSD, MVP
http://Steve.Orr.net
"ven" <venome_@.poczta.onet.pl> wrote in message
news:cif6p8$sf3$1@.news.onet.pl...
> How must i declare my variables to have this code work. I get
> system.nullreferenceexception every time i click button to add data to
> datatable
> here below is my code :
> Dim wykszt as System.Data.DataTable
> Dim zatru as System.Data.DataTable
> Private Sub Page_Load(s As Object, e As EventArgs)
> if Not IsPostBack Then
> make_d_tables()
> End if
> End Sub
> sub make_d_tables()
> wykszt = New System.Data.DataTable("wykszt")
> wykszt.Columns.Add("od_data", GetType(date))
> wykszt.Columns.Add("do_data", GetType(date))
> wykszt.Columns.Add("nazwa_szkoly", GetType(String))
> wykszt.Columns.Add("nazwa_tytulu", GetType(String))
> zatru = New System.Data.DataTable("zatr")
> zatru.Columns.Add("od_data", GetType(date))
> zatru.Columns.Add("do_data", GetType(date))
> zatru.Columns.Add("nazwa_prac", GetType(String))
> zatru.Columns.Add("nazwa_stan", GetType(String))
> End sub
> Sub Button2_Click(sender As Object, e As EventArgs)
> row = wykszt.NewRow
> row("od_data")=TextBox27.Text + "-01"
> row("do_data")=TextBox28.Text + "-01"
> row("nazwa_szkoly")=TextBox29.Text
> row("nazwa_tytulu")=TextBox30.Text
> wykszt.Rows.Add(row)
> row = wykszt.NewRow
> Mxdatagrid1.datasource=wykszt
> Mxdatagrid1.databind
> End Sub
>
> Thanks
> Pat
>
Uytkownik "Steve C. Orr [MVP, MCSD]" <Steve@.Orr.net> napisa w wiadomoci
news:OkGuVzNnEHA.1304@.TK2MSFTNGP09.phx.gbl...
> Which line is throwing the exception?
> Does the error only happen on postback?
> --
> I hope this helps,
> Steve C. Orr, MCSD, MVP
> http://Steve.Orr.net
>
> "ven" <venome_@.poczta.onet.pl> wrote in message
> news:cif6p8$sf3$1@.news.onet.pl...
>
sorry i left behind that i have Dim row as System.Data.DataRow in my
declarations too
but exception is only when i post back and
on this line :
row = wykszt.NewRow
and a full stack :
Szczegy wyjtku: System.NullReferenceException: Odwoanie do obiektu nie
zostao ustawione na wystpienie obiektu.
Bd rda:
Wiersz 35: Sub Button2_Click(sender As Object, e As EventArgs)
Wiersz 36:
Wiersz 37: row = wykszt.NewRow
Wiersz 38: row("od_data")=TextBox27.Text + "-01"
Wiersz 39: row("do_data")=TextBox28.Text + "-01"
Plik rdowy: c:\inetpub\wwwroot\axell\forma.aspx Wiersz: 37
lad stosu:
[NullReferenceException: Odwoanie do obiektu nie zostao ustawione na
wystpienie obiektu.]
ASP.forma_aspx.Button2_Click(Object sender, EventArgs e) in
c:\inetpub\wwwroot\axell\forma.aspx:37
System.Web.UI.WebControls.Button.OnClick(EventArgs e) +108
System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePo
stBackEvent(String eventArgument) +58
System.Web.UI.Page. RaisePostBackEvent(IPostBackEventHandler
sourceControl, String eventArgument) +18
System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +33
System.Web.UI.Page.ProcessRequestMain() +1277
sorry for polish language
Thanks
Pat
In that case I agree with Marina.
You need to recreate your table upon each postback.
Right now you aren't doing that, so you can't add a row to a table that
doesn't exist, thus your error.
Remove the If statement in Page_Load.
I hope this helps,
Steve C. Orr, MCSD, MVP
http://Steve.Orr.net

> sorry i left behind that i have Dim row as System.Data.DataRow in my
> declarations too
> but exception is only when i post back and
> on this line :
> row = wykszt.NewRow
> and a full stack :
> Szczegy wyjtku: System.NullReferenceException: Odwoanie do obiektu nie
> zostao ustawione na wystpienie obiektu.
> Bd rda:
> Wiersz 35: Sub Button2_Click(sender As Object, e As EventArgs)
> Wiersz 36:
> Wiersz 37: row = wykszt.NewRow
> Wiersz 38: row("od_data")=TextBox27.Text + "-01"
> Wiersz 39: row("do_data")=TextBox28.Text + "-01"
>
> Plik rdowy: c:\inetpub\wwwroot\axell\forma.aspx Wiersz: 37
> lad stosu:
> [NullReferenceException: Odwoanie do obiektu nie zostao ustawione na
> wystpienie obiektu.]
> ASP.forma_aspx.Button2_Click(Object sender, EventArgs e) in
> c:\inetpub\wwwroot\axell\forma.aspx:37
> System.Web.UI.WebControls.Button.OnClick(EventArgs e) +108
> System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.Raise
Po
> stBackEvent(String eventArgument) +58
> System.Web.UI.Page. RaisePostBackEvent(IPostBackEventHandler
> sourceControl, String eventArgument) +18
> System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +33
> System.Web.UI.Page.ProcessRequestMain() +1277
> sorry for polish language
> Thanks
> Pat
>