Trying again!!

[nacho2]

Hi everyone, I posted this question but got no answer, can somebody help me out!!??

I'm trying to update my xml database.

I have a table called Clients (columns: Id, Name,..., Erased), and I'm trying to modify the column Erased from False to True (yes it is a boolean column).

I only want to modify the dataset and then run dataset.writexml, there is no sql database or any other external database.

I know there is a command dataset.select() for selecting rows but isn't there anything for updating??? (changing one value of one column of one row)

Erasing a column and then adding the changed one won't work because the database won't let me because there are table relations and erasing one would be incoherent. And adding the row first and then erasing the old one won't work either because Id is a primary key and is unique.

Thanks for your help!!!

[nacho2]

Hi guys does anyone have any idea on how to do this?

Thanks

[Asgorath]

Hi Nacho2
I think you won't get much help from the forum because no one in its in right mind would consider xml as a database engine : use access, ms sql, msde,mysql, etc...

Anyway check the System.Xml.XmlDataDocument class that allows for xml node managment.

Regards
Jorge

[nacho2]

Ok, Jorge, you are probably right but I think it is basically the same. If I were using a SQL database I would fill my dataset and then make changes to it and afterwards send those changes to the database. So I don't think it makes a big difference where you are storing your data, the only differences are between the dataset and the database whereas my questions are about the 'space' between the dataset and the user. Does it make sense?

If you had a SQL and filled a Dataset, how would you retrieve data from the dataset to show the user? Using dataset.select(..)? And how would you make changes to the dataset?

[Asgorath]

Ok, this is how i make a update to a datarow. I have a datatable named m_DataTable with 3 datacollumn named 'Column0','Column1' and 'Column2'. I added to the datatable 3 datarows initially with the values (1,2,3), (4,9,12) and (77, 192,0).

        m_DataTable.AcceptChanges()
        '' update 1st row
        m_DataTable.Rows(0)("Column0") = "cat"
        m_DataTable.Rows(0)("Column1") = "dog"
        m_DataTable.Rows(0)("Column2") = "horse"
        '' update 2nd row
        m_DataTable.Rows(1)("Column0") = "cat"
        m_DataTable.Rows(1)("Column1") = "dog"
        m_DataTable.Rows(1)("Column2") = "horse"
        '' update 3rd row
        m_DataTable.Rows(2)("Column0") = "cat"
        m_DataTable.Rows(2)("Column1") = "dog"
        m_DataTable.Rows(2)("Column2") = "horse"

        Me.DataGrid1.DataSource = m_DataTable

Once you modified the datarows just update your xml files with the dataset.

Regards
Jorge

[nacho2]

Ok great that's what I needed.

Now one more thing, what if I don't know the row index? Let's say it is a table of customers having each customer an IdCustomer. How can I get the row index that corresponds to the row with the IdCustomer I have?

I've tried doing:

DataSchema1.Clientes.Select("IdCustomer=" & var)
DataSchema1.Clientes.Rows(0)("Name") = "NewName"
DataSchema1.WriteXml("..\Data.xml")

I did the select first thinking that that would leave DataSchema1.Clientes with only the row with IdCustomer= var but I guess I would have to store it somewhere, and not just the method.

So then I thought there may be some method to get the row index of certain row.

Any ideas?

Thanks

[Asgorath]

Ok great that's what I needed.

Now one more thing, what if I don't know the row index? Let's say it is a table of customers having each customer an IdCustomer. How can I get the row index that corresponds to the row with the IdCustomer I have?

I've tried doing:

DataSchema1.Clientes.Select("IdCustomer=" & var)
DataSchema1.Clientes.Rows(0)("Name") = "NewName"
DataSchema1.WriteXml("..\Data.xml")

I did the select first thinking that that would leave DataSchema1.Clientes with only the row with IdCustomer= var but I guess I would have to store it somewhere, and not just the method.

So then I thought there may be some method to get the row index of certain row.

Any ideas?

Thanks

Hi
Try this

Dim filter As String = "IdCustomer='" & var & "'"
Dim r As DataRow() = DataSchema1.Clientes.Select(filter)
For j As Integer = 0 To r.Length - 1
    MessageBox.Show(r(j).Item(1).ToString)
Next

Regards
Jorge

[nacho2]

Thanks Jorge,

I already figured out that there was no predefined function to get the row index so I wrote my own, which looks a lot like yours.

I really appreaciate your help, thank you very much.

Gracias!

Nacho

[Edneeis]

You can also use the Select method you mentioned before to get an array of datarows that meet your criteria and then change the value. That should be faster than looping to find it.

Dim dr() As DataRow=DataTable1.Select(String.Format("IdCustomer={0}",var))
If dr.Length > 0 Then
   dr(0)("Erased")=False
End If