Help on DataSets

22 Jul 2006 8:02 PM

Dot Net Daddy

Hello,

I am creating an application using asp.net 2.0. But I am stuck
somewhere. I want to get values from a DataSet one by one on every
Page_Load. So I wrote my code in Page_Load but it didnt work, giving a
warning. Here is my code:

[code]
    Protected Sub Page_Load(ByVal sender As Object, ByVal e As
System.EventArgs) Handles Me.Load
        Dim ds As DataSet1
        Dim test As String
        test = ds.Tables("pictureID").Rows(0)("pictureID").ToString
        Label1.Text = test
    End Sub
[/code]

And the Warning:

Variable 'ds' is used before it has been assigned a value. A null
reference exception could result at runtime.

How can I handle this warning. Did I wrote the code in wrong place?

I created my DataSet using the menu in Visual Web Developer (Visual
Studio 2005). So I did not write any code for it.

Am I assigning the ds right?
I also assigned it as DataSet1TableAdapter. But it didnt work also. I
am a rookie so any help is appreciated.

23 Jul 2006 5:02 AM

Cor Ligthert [MVP]

DotNetDaddy,

If you want to get individual results focus you than on the datatable. The
dataset is just a very extended wrapper arround that (and around the
relations to that).

Your error is because "ds" in your code is only a placeholder address for an
object which is not filled yet (Is Nothing). You have to set it to, to the
actual object as is created. (Or use that direct)

Cor

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"Dot Net Daddy" <cagrian***@gmail.com> schreef in bericht
news:1153598571.054394.64430@m73g2000cwd.googlegroups.com...
> Hello,
>
> I am creating an application using asp.net 2.0. But I am stuck
> somewhere. I want to get values from a DataSet one by one on every
> Page_Load. So I wrote my code in Page_Load but it didnt work, giving a
> warning. Here is my code:
>
> [code]
>    Protected Sub Page_Load(ByVal sender As Object, ByVal e As
> System.EventArgs) Handles Me.Load
>        Dim ds As DataSet1
>        Dim test As String
>        test = ds.Tables("pictureID").Rows(0)("pictureID").ToString
>        Label1.Text = test
>    End Sub
> [/code]
>
> And the Warning:
>
> Variable 'ds' is used before it has been assigned a value. A null
> reference exception could result at runtime.
>
>
> How can I handle this warning. Did I wrote the code in wrong place?
>
> I created my DataSet using the menu in Visual Web Developer (Visual
> Studio 2005). So I did not write any code for it.
>
> Am I assigning the ds right?
> I also assigned it as DataSet1TableAdapter. But it didnt work also. I
> am a rookie so any help is appreciated.
>

24 Jul 2006 2:30 AM

tomb

You need to make ds = New DataSet1, then populate the dataset with data.

T

Dot Net Daddy wrote:

Show quoteHide quote

>Hello,
>
>I am creating an application using asp.net 2.0. But I am stuck
>somewhere. I want to get values from a DataSet one by one on every
>Page_Load. So I wrote my code in Page_Load but it didnt work, giving a
>warning. Here is my code:
>
>[code]
>    Protected Sub Page_Load(ByVal sender As Object, ByVal e As
>System.EventArgs) Handles Me.Load
>        Dim ds As DataSet1
>        Dim test As String
>        test = ds.Tables("pictureID").Rows(0)("pictureID").ToString
>        Label1.Text = test
>    End Sub
>[/code]
>
>And the Warning:
>
>Variable 'ds' is used before it has been assigned a value. A null
>reference exception could result at runtime.
>
>
>How can I handle this warning. Did I wrote the code in wrong place?
>
>I created my DataSet using the menu in Visual Web Developer (Visual
>Studio 2005). So I did not write any code for it.
>
>Am I assigning the ds right?
>I also assigned it as DataSet1TableAdapter. But it didnt work also. I
>am a rookie so any help is appreciated.
>
>
>