databinding to hidden textbox

[escape0]

hi!

I've a problem binding a datafield to a textbox which has the property visible set to false. After reading the data from the database the textbox doesn't contain a value... if i set visible to true it work's.

I'm using the hidden textbox to store an ID-value for further db-operations (update, delete...) Is this a bug? How can i handle this problem?

thanks
Robert

[MrGTI]

Personally i never bind anything to a database, but i do i have a suggestion.

It sounds like a bug to me, so i would suggest you leave the TextBox visible, and in the form load event, just change the .Left property of the TextBox to be off the left side of the form (ie: a value of -100).

You might also want to turn off the tab ability for that control as well - just so the user can't get to it.

[Lunatic3]

Do not set the Visible Property to False Just hide that textbox on load event of form.
Textbox1.Hide()

[Pirate]

As another perfect option is : FORGET binding . It's messy . I've read a lot of articles say it's full of bugs . Another reason when you have your own code is to make your methods *reusable* .
Just a thought

[escape0]

forget binding... ok... that's an idea! in vb6-projects i never used databinding but in .net i never had problems with it. BUT i do not like it.

So what is the best way to 'forget it'?

onload:
- fill a dataset
- assign the values of the dataset to the textboxes (or whatever)

event - save:
- assign the valuse of the textboxes to to dataset
- update dataset

before closing a form i always check if changes are made but i think this will not be a problem because doing it without databinding i also can check the dataset.haschanges-property.

pirate you wrote about reusable methods... what do you mean with this?

[Pirate]

Originally posted by escape0
pirate you wrote about reusable methods... what do you mean with this?

When you make your code reusable it means you don't have to rewrite the code all over again (could be little changes) . Just build these functions in a class or module then you can export it to dll file , whenever you need it just call that file . This saves time and effort .

assigning values to db field/textbox is a peice of cake .See my exmple in this thread ...http://www.vbforums.com/showthread.p...hreadid=240656
hope that's clear !

[escape0]

you're right... it's much easier to use own code instead of databinding but there is one problem i mentioned above.

if the user quits the transaction (=form) i want to check if changes were made and ask the user if he want's to save them. i assign the values of the textboxes to the dataset-fields without checking whether the user changed them or not.

the dataset.haschanges-property is always true... i think .net sets this property if only a value is assigned to a field even if it is the same value.

anybody an idea how to solve this?

[Pirate]

Is your problem have to do with saving or editing data ?
I built this class which shows your how to save to db .
Put your verification and checking rules before updating it .

Public Class Class1
 
    'Libraries needed for running this Code
        Imports System.Data
        Imports System.Data.OleDb
 
    'open Connection to the Database with Password
    Dim MyPath As String = Application.StartupPath & "\__mydb__.mdb"
    Dim MyPassword As String = "passme"
    Dim StrSQL As String = "Select * From MyTable"
    Dim MyConnection As New 
OleDb.OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & 
MyPath & ";Jet OLEDB:Database Password=" & MyPassword)
        MyConnection.Open()
 
    'This Saves data to a DataSet and then uses update method
    'against Database Source File
    Dim MyCommand As New OleDbCommand(StrSQL, MyConnection)
    Dim MyDataset As DataSet = New DataSet()
    Dim MyAdapter As New OleDb.OleDbDataAdapter(StrSQL, MyConnection)
 
 
        MyAdapter.Fill(MyDataset, "MyTable")
    Dim MyDataRow As DataRow = MyDataset.Tables("MyTable").NewRow
    'Fill the data in Four Columns in the Database (Fields)
        MyDataRow("1_Column") = Textbox1.Text
        MyDataRow("2_Column") = Textbox2.Text
        MyDataRow("3_Column") = Textbox3.Text
        MyDataRow("4_Column") = Textbox4.Text
        MyDataset.Tables("MyTable").Rows.Add(MyDataRow)
        MyAdapter.Update(MyDataset, "MyTable")
        MessageBox.Show("Data Saved..", "Saved",
 
    'if you want to write the data as well to XML file then you
    'include(this)before update method
        MyDataset.WriteXml(Application.StartupPath & "\_MyXMLFile_.XML")
    End Sub
 
End Class
'''''''''''''''''''''
'By Pirate
'..............

[escape0]

the problem is to save the data... the user should only be asked to save if the data was changed.

i think i've to check whether the value of the datasetfield is different from that of the textbox and only assign if there is a difference.

in your example you add a row to the db... i do this in a similar way but i want to know which ID the added row gets from the db (autoimcrement field).

this is my coding... in austria we would say 'with the cross around the curch' (means not efficient or complicated). maybe there's a much easier way!?!? (look at the comments --->1 & 2)

Public Function addnew(ByVal iArt As Integer, _
                           ByVal iMandantID As Integer, _
                           ByVal iParentID As Integer) As dsBilanzaufbau
        Try
            Dim dr As SqlDataReader
 
            ' nächste freie SortID ermitteln
            Dim iNextSortID As Integer
            strSQL = "SELECT TOP 1 Sort_ID FROM tbl_cu_bilanzaufbau WHERE Mandant_ID = " & iMandantID & " AND Parent_ID = " & iParentID & " ORDER BY Sort_ID DESC"
            dr = objSQL.getDataReader(strSQL)
            If dr.Read() = True Then
                iNextSortID = CInt(dr.Item("Sort_ID")) + 1
            Else
                iNextSortID = 1
            End If
            objSQL.closeDataReader(dr)
 
            Dim dRow As DataRow
            dRow = ds.tbl_cu_bilanzaufbau.NewRow()
            objSQL.initDataRow(dRow)
 
            dRow.Item("ID") = 0
            dRow.Item("Mandant_ID") = iMandantID
            Select Case iArt
                Case 1
                    dRow.Item("Typ") = "O"
                    dRow.Item("Bezeichnung") = "neuer Ordner"
                Case 2
                    dRow.Item("Typ") = "K"
                    dRow.Item("Bezeichnung") = "neue Bilanzzeile"
            End Select
            dRow.Item("Parent_ID") = iParentID
            dRow.Item("Sort_ID") = iNextSortID
            dRow.Item("AendBenutzer") = aktBenutzer
            dRow.Item("AendTimestamp") = Format(DateTime.Now(), "dd.MM.yyyy") & " " & Format(DateTime.Now(), "HH:mm")
 
            ds.tbl_cu_bilanzaufbau.Rows.Add(dRow)
 
            strSQL = "SELECT TOP 1 * FROM tbl_cu_bilanzaufbau ORDER BY ID DESC"
            da = objSQL.configAdapter(strSQL)
            save()
            ds.Clear()
 
            ' --->1
            ' read ID of the row added before
            Dim iID As Integer
            iID = objSQL.getLastID(strTablename, "ID")
 
            ' --->2
            ' fill dataset with row added before
            ds = readByID(iMandantID, iID)
 
            Return ds
 
        Catch ex As Exception
            objError.raiseSysError("cls_sql_bilanzaufbau", "", "save", ex.Message, "")
        End Try
 
    End Function

As you see i have to read the row i added befor in a second step (ds = readByID(iMandantID,iID)). Is there a way to get the autoincremended ID-Value when updating the dataset?

I know that this has nothing to do with my original problem but maybe you also had this problem some time ago...

[Pirate]

Well , I don't know why I don't like autonumber field . It doesn't make any sense to me at least .

[escape0]

ok but without autonumber-filds you've the same problem as me.

my problem:
1. save row with id = 0
2. read row with highest id

your problem:
1. read row with highest id (=x)
2. save row with id = (x+1)

the time between step 1 and 2 are critical because in a multiuser-environment this could cause problems in the database. in my opinion this has to be a feature of ADO.NET in order to make such a db-operation secure.

BUT... that's another story.

thank you pirate for your help

[Pirate]

I'm still unable to well understand your problem (been working on such db apps more than 3years) . Establish your own rules of opening your database (for ex . exclusive use or not) and data entering (one or two or whatever at specific time with/out limited access ) . When you add new row , it will be added to the database (here you have to check first if it's existed already then prevent the user if not add new record ) . For me , I never consider what you posted as problem , never .