Auto update access tables Cells with random numbers from vb.net - vb.net

Question

I searched many forums but didn't find any solution. I want to update access table cells from Vb.net. My table has fields:
[PanelNumber],[Date], [PVValue]
In Panel number field, there is some text like "Panel 1", "Panel 2" etc..
from vb, i will select that "Panel 1" after clicking a button, i need to fill that "PVValue" field with random numbers in given range, plz check my code below, when i try with this code, i am always getting same number in all rows
but need separate number (may be repeated in some rows)
LogTable2 is my table name
Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
connString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=LoggedData.accdb;Jet OLEDB:Database Password=GodavarthiSuresh;"
myNewConnection.ConnectionString = connString
myNewConnection.Open()
Dim UpdateString As String = "update LogTable2 set [pvvalue]= #rndVal1 where panelnumber='" & panelnametxt.Text & "'"
Dim UpdateCmd As New OleDb.OleDbCommand(UpdateString, myNewConnection)
UpdateCmd.Parameters.Clear()
Randomize()
UpdateCmd.Parameters.AddWithValue("#rndVal1", GetRandom())
Try
UpdateCmd.ExecuteNonQuery()
UpdateCmd.Dispose()
myNewConnection.Close()
Catch ex As Exception
MsgBox(ex.Message)
End Try
End Sub
' this is the function to get random number in given range
Public Function GetRandom() As Integer
Static Generator As System.Random = New System.Random()
Return Generator.Next(825, 850)
End Function

Answer 1

If you have multiple rows for each panel and you want them to have different values, you need to update them individually. Its is not true that update command will be "called" 5 times if there are five rows associated. It will be executed once per click event.
To do what it sounds like you want, you need a unique identifier for each such as an AutoIncrement ID column.
Private RNG As New Random()
Private Sub btnUpdate_Click(etc...
Dim sql = "SELECT ID FROM LogTable2 WHERE panelnumber = #pnl"
Dim pnlList As New List(Of Int32)
Using con As OleDbConnection = GetACEConnection()
Using cmd As New OleDbCommand(sql, con)
con.Open()
cmd.Parameters.AddWithValue("#pnl", panelnametxt.Text)
' get affected row IDs into a list;
Using rdr As OleDbDataReader = cmd.ExecuteReader
While rdr.Read
pnlList.Add(Convert.ToInt32(rdr.Item("ID")))
End While
End Using ' close, dispose of reader
End Using ' dispose of cmd
' not sure you need a new command object
sql = "UPDATE LogTable2 SET pvvalue = #rVal WHERE ID = #id"
Using pcmd As New OleDbCommand(sql, con)
' loop thru ID list and update each row with
' new random value 825-849 inclusive
For n As Int32 = 0 To pnlList.Count - 1
pcmd.Parameters.AddWithValue("#rVal", RNG.Next(825, 850))
pcmd.Parameters.AddWithValue("#id", pnlList(n))
pcmd.ExecuteNonQuery()
' clear for next iteration
pcmd.Parameters.Clear()
Next
End Using ' close and dispose of pcmd
End Using ' close and dispose of connection
End Sub
I dont like scattering the connection string in every method which opens a connection, so a method for that is nice to have.
Notes:
This depends on a unique ID column which is AutoIncrement (PK). If you have some other unique identifier, use it but you have to have some way to identify rows individually.
Rather than a method to create a random value, since it is just one line, it might be easier to just use your RNG directly as shown.
I cant test the code, but it should be close.
Use Using blocks to close and dispose of DBObjects like connections, command and reader otherwise you can run out of resources.
You can also initialize Command objects with the SQL and COnnection when you declare it rather than setting them as properties. It makes the code a little more compact and less likely that you forget them.
Randomize does nothing - it is meant to be used with the old VB6 Rnd(). You only need to [Escape] keywords in SQL, not every column name and pvvalue is not a keyword.
A DataTable instead of a Reader could be used to get the rows but I am not sure it is any simpler.
Finally, elements of a SQL WHERE clause can also be parameterized; there is no need to concat them just because it is a where rather than a column value.

Answer 2

you can do this in database level,add auto increment value to database field