Using the DataSet Namespace

[tina33]

Hi Good People

I'm a newbie in .NET and looking for help in getting my small project started. I'm using textbox controls on a form to capture some details and create an in-memory cache of my records before I eventually save the collection of records created to an XML file.

The form will also have commandbuttons to allow me to insert a new record, go next record, got first record, etc (similar to the methods of a recordset). Each time I navigate to a different record, the textbox contents on the form should reflect the change. A SUBMIT command button should write all these records in memory to an XML file.

How can I allow navigation from one record to another, as well as record changes just the way we do in VB6.0 using the Recordset object? I couldn't see any way of doing it. Which object(s) in the Dataset namespace can I use?

PLEASE HELP!! Here's a simplified version of my code snippet:

Public Shared Sub SaveRecordsInDatatable
CreateDataSet
'Add data to table
Dim i As Integer
For i = 0 To 10
dr = dt.NewRow
dr("name") = txtName.text
dr("surname") = txtSurname.text
dr("DOB") = txtDOB.text
dt.Rows.Add(dr)
Next i

End Sub

Public Shared Sub CreateDataset()
Dim dt As New DataTable
Dim dc As DataColumn
Dim dr As DataRow

' Create new DataRow objects
'create name column
dc = New DataColumn
dc.DataType = System.Type.GetType("System.String")
dc.ColumnName = "name"
dt.Columns.Add(dc)

' Create surname column.
dc = New DataColumn
dc.DataType = Type.GetType("System.String")
dc.ColumnName = "surname"
dt.Columns.Add(dc)

' Create Date Of Birth column.
dc = New DataColumn
dc.DataType = Type.GetType("System.String")
dc.ColumnName = "DOB"
dt.Columns.Add(dc)
End Sub


P/S - some code snippets would help. Thanks.

[Pirate]

http://www.vbforums.com/showthread.p...79#post1662879

[taxes]

Hi,

Looking at your code I think there are problems when you declare private objects within a Shared Sub. I also don't think that having declared the objects as private within a sub you can refer to them outside of that sub.

I personally have found it easier to use a DataTable to update tables, rather than a Dataset. I have also found navigation easier in a DataTable. But remember that you can use only one table in a DataTable and if you use an SQL query referring to more than one table, you have to use a DataSet.

Having relooked at your code I notice that you have not actually used a DataSet, even though you name your Sub that way!!!

I have to go and play tennis now. If you have not received more helpful responses I will revert leter.

[tina33]

Thanks taxes. You are right; with the way I wrote my code, it wouldn't work. I was trying to quickly explain my problem in a way that could be understod, but in the process I got sloppy.

I will be happy if you explain to me further.

[taxes]

Hi,

"How can I allow navigation from one record to another, as well as record changes just the way we do in VB6.0 using the Recordset object? I couldn't see any way of doing it. Which object(s) in the Dataset namespace can I use? "


I'll stick to this part of your posting - I'm not sure I quite understand your first part


Assuming your are accessing a single table on an Access database:

In the general section of your form;

Dim cn1 as New Oledb.OledbConnection
Dim da1 as New Oledb.OledbDataAdapter
Dim cb1 as New Oledb.OledbCommandBuilder
Dim dt1 as New DataTable
Dim iRowPosition as Integer=0
Dim rw1 as DataRow
Dim iCount as Integer


In the form Load event:

cn1.ConnectionString="Provider=Microsoft.Jet.oledb.4.0;Data Source=pathto database

cn1.Open

da1=New Oledb.OledbDataAdapter("Select * from tablename",cn1)

cb1= New Oledb.OledbCommandBuilder(da1)

da1.Fill(dt1)


You can now navigate through the DataTable using

rw1.Rows(iCount)

e.g. txt1.text=dt1.Rows((iCount)("FieldName").ToString()

Se how you get on with that (As I have spent so much time at tennis and on the internet, I now have to do penance in the garden)

EDIT: If you are familiar with Imports then you can cut down on the use of "Oledb"

[tina33]

Hi

Thanks for your advice. i'm afraid it's a bit more complicated than that. I'm not accessing any database but using XML, and I don't know how to bind my controls to the datatable.

Here's the process:
I'll create an in-memory blank DataTable first, add rows to the table, then send the result for processing via a message queue. The final message will consist of one message header and several transaction details (in this case the rows in my Datatable).

Before I send this message for processing, I need to be able to insert new rows, change any row details, delete any unwanted rows, etc (just like I do if I was using the recordset object).

Any advice? Thanks.

[taxes]

Hi,

Ah. Then as far as adding new rows, your code should work - provided you make the declaration amendments previously mentioned. Have you tried it? If so what errors?

You can navigate the table exactly as I posted and make the data visible in textBoxes etc by

txt1.text=dt.Rows(x)("Surname").ToString

x being the number of the row you want to view.

[tina33]

Thanks so much Taxes. It worked!!

Now all I have to do is see if I can add other functionality.

Cheers.