VB store list of records in a text file and read back - vb.net

Question

I have a VB program in VS2017. It reads many excel files and store relevant data in
Dim total_sessions As New List(Of Session_CSV_file)
The list is big (~10k), and includes about 20 fields each.
Is there a way in VB to store it in a file in one command and read it later on easily., without reading and writing each field?
Often I need to debug the later part. I prefer doing it without rerunning the whole first part.
Or is there a way in Visual Studio, to stop the run at a certain point, and store this point in a dump file, like simulators often do? (so they can run the simulation from this point later on)

Answer 1

Perhaps if you load your csv data into a DataTable instead:
Dim dt as New DataTable
dt.Columns.Add("Name")
dt.Columns.Add("Age", GetType(Int32))
For Each filepath in tenKFilePaths
For Each line in File.ReadAllLines(file)
Dim bits = line.Split(","c)
dt.Rows.Add(bits(0), Convert.ToInt32(bit(1))
Next line
Next filepath
Then you can save the whole lot to xml:
dt.WriteXml("c:\temp\my.xml")
Have a coffee, reboot etc the read them again and carry on where you left off:
Dim dt2 as New DataTable
dt2.ReadXml("c:\temp\my.xml")
Raw datatables are a bit difficult to work with because you end up accessing their rows and column data by string indexing and having to cast it a lot - fairly lame. There is a better way to use them, as visual studio can create custom classes that inherit from the base datatables and offer lots of functionality that does away with all the awkwardness of dealing with datatables as a very generic thing. Just like the forms designer creates a UI form that inherits from Form, the dataset designer creates custom datatables that inherit from the base
If you add a new DataSet type object to your project, double click it it opens something like a database designer. Right click that surface and choose Add DataTable, Add your Columns with their respective datatypes etc - this is the equivalent of your Session_Csv_File class, with its properties and fields. Double click on it and you can add code etc - if your session_csv_file has custom methods you can transfer their code to the custom data row
Imagine I created a new datatable in a DataSet and called it SessionCsvFiles. Imagine I added a Name and Age column, and I added a custom method called BlahBlah
I'd then be able to say in code things like:
Dim dt as New MyCustomDataSet.SessionCsvFilesDataTable
'it's like making a new SessionCsvFile
Dim r = dt.NewSessionCsvFilesRow()
'It's like setting your properties
r.Name = csvBits(0)
r.Age = Convert.ToInt32(csvBits(1))
'It's like adding your file to the List
dt.Add(r)
You now have virtually the same thing as you had before - a collection of objects that represents things about your csv files. The difference is with this route it has an already-built-in way of saving all the properties and the collection to xml and reading it back again

Answer 2

Add the Serializable attribute to the Class. I added a parameterized constructor for ease in building my list but you must provide a constructor without parameters for this to work. Thus, the empty Sub New.
<Serializable()>
Public Class Session_CSV_file
Public Property ID As Integer
Public Property Name As String
Public Property Type As String
Public Sub New()
End Sub
Public Sub New(SessID As Integer, SessName As String, SessType As String)
ID = SessID
Name = SessName
Type = SessType
End Sub
End Class
The add Imports System.Xml.Serialization to the top of the file.
Private Sub SaveList()
Dim serializer = New XmlSerializer(GetType(List(Of Session_CSV_file)))
Using writer As New StreamWriter("C:\Users\xxx\Documents\XMLtest.xml")
serializer.Serialize(writer, lst)
End Using
End Sub
I filled my list as follows but you can fill you list any way you choose.
Private lst As New List(Of Session_CSV_file)
Private Sub FillList()
Using cn As New SqlConnection(My.Settings.CoffeeConnection),
cmd As New SqlCommand("Select Top 10 * From Coffees;", cn)
cn.Open()
Dim reader = cmd.ExecuteReader
While reader.Read
Dim sess As New Session_CSV_file(reader.GetInt32(0), reader.GetString(1), reader.GetString(3))
lst.Add(sess)
End While
End Using
End Sub
To recreate the list... (OOps! forgot this)
Private RehydratedList As New List(Of Session_CSV_file)
Private Sub CreateListFromXML()
Dim serial As New XmlSerializer(GetType(List(Of Session_CSV_file)))
Using fs As New FileStream("C:\Users\maryo\Documents\XMLtest.xml", FileMode.Open)
RehydratedList = DirectCast(serial.Deserialize(fs), List(Of Session_CSV_file))
End Using
For Each item In RehydratedList
Debug.Print(item.ToString)
Next
End Sub