如何使用 Visual Studio 2019 (VB.NET) 按钮在 Access 数据库中创建新记录

Question

DISCLAIMER: I'm very new to coding and programming; sorry if the coding is subpar.

My goal is to have my Visual Studio 2019 project (named Detailing Error Log) add a new record/ row into my Microsoft Access Database table (accdb file named Database1, table named Data Collection) based on which checkboxes are checked. I would only like rows to be added, not deleted, whenever the "Import" button is clicked. The Database will then be saved and the checkboxes in my Visual Studio project unchecked. The Database will be used to store that data until it is used by a coordinating visual studio program to count the occurrences of specific text within a specific month. From there it will be displayed in graphs.

I had successfully done this using Excel; but experienced too much lag whenever there were multiple entries.

My problem is that I am getting this error from my " dsnewrow " variable:

System.NullReferenceException: 'Object reference not set to an instance of an object.' System.Data.DataTableCollection.this[string].get returned Nothing.

So I was looking around on Google and programming forums, and I didn't really find any posts that I believe matched what I'm trying to accomplish: the adding of a new record each time the "Import" button is clicked. Is my code to add a new record correct? I saw a couple of different ways new records were "added", but by looking at the similar posts I thought this one was my best option.

Below is my code, thanks for the help::

NEATOL = No Entries At the Time Of Log

Private Sub ConnectionPrep(sender As System.Object, e As System.EventArgs) Handles MyBase.Load

    Dim dbProvider As String
    Dim dbSource As String
    Dim sql As String
    Dim inc As Integer
    Dim MaxRows As Integer
    Dim con As New OleDb.OleDbConnection
    dbProvider = "PROVIDER=Microsoft.ACE.OLEDB.12.0;"
    dbSource = "Data Source = S:\software\Melton System\DPD & DEL (KPI)\Database1.accdb; Persist Security Info = False"
    con.ConnectionString = dbProvider & dbSource
    con.Open()
End Sub

Private Sub InputInformation(sender As System.Object, e As System.EventArgs) Handles ImporttBUT.Click
    Dim con As New OleDb.OleDbConnection
    Dim ds As New DataSet
    Dim da As OleDb.OleDbDataAdapter
    Dim cb As New OleDbCommandBuilder()
    Dim dsnewrow As DataRow
    dsnewrow = ds.Tables("Data Collection").NewRow()
    dsnewrow.Item("M/Y OF LOG") = Me.MonthList2021.SelectedItem
    dsnewrow.Item("TIME OF LOG") = DateTime.Now.ToString("MM/dd/yyyy HH:mm:ss")
    dsnewrow.Item("USER") = UserName
    dsnewrow.Item("STOCK NUMBER") = Me.StockNumberTXTB.Text
    If MissedPartCHKB.Checked = True Then
        dsnewrow.Item("MISSED PART") = Me.MissedPartCHKB.Text
    ElseIf MissedPartCHKB.Checked = False Then
        dsnewrow.Item("MISSED PART") = "NEATOL"
    End If
    If NotInEpicorCHKB.Checked = True Then
        dsnewrow.Item("NOT IN EPICOR") = Me.NotInEpicorCHKB.Text
    ElseIf NotInEpicorCHKB.Checked = False Then
        dsnewrow.Item("NOT IN EPICOR") = "NEATOL"
    End If
    If MissedBuyoutCHKB.Checked = True Then
        dsnewrow.Item("MISSED BUYOUT") = Me.MissedBuyoutCHKB.Text
    ElseIf MissedBuyoutCHKB.Checked = False Then
        dsnewrow.Item("MISSED BUYOUT") = "NEATOL"
    End If
    If NonStockCHKB.Checked = True Then
        dsnewrow.Item("MISSED NON STOCK ITEM") = Me.NonStockCHKB.Text
    ElseIf NonStockCHKB.Checked = False Then
        dsnewrow.Item("MISSED NON STOCK ITEM") = "NEATOL"
    End If
    If MissedSTKItemCHKB.Checked = True Then
        dsnewrow.Item("MISSED STOCK ITEM") = Me.MissedSTKItemCHKB.Text
    ElseIf MissedSTKItemCHKB.Checked = False Then
        dsnewrow.Item("MISSED STOCK ITEM") = "NEATOL"
    End If
    If MissedAutomatedPartCHKB.Checked = True Then
        dsnewrow.Item("MISSED AUTOMATED") = Me.MissedAutomatedPartCHKB.Text
    ElseIf MissedAutomatedPartCHKB.Checked = False Then
        dsnewrow.Item("MISSED AUTOMATED") = "NEATOL"
    End If
    If MissingPrintAfterQTYCHKB.Checked = True Then
        dsnewrow.Item("MISSING PRINTS AFTER QUANTITY") = Me.MissingPrintAfterQTYCHKB.Text
    ElseIf MissingPrintAfterQTYCHKB.Checked = False Then
        dsnewrow.Item("MISSING PRINTS AFTER QUANTITY") = "NEATOL"
    End If
    If MissedPrintsNOTSentChadCHKB.Checked = True Then
        dsnewrow.Item("MISSED PRINT NOT SENT TO CHAD") = Me.MissedPrintsNOTSentChadCHKB.Text
    ElseIf MissedPrintsNOTSentChadCHKB.Checked = False Then
        dsnewrow.Item("MISSED PRINT NOT SENT TO CHAD") = "NEATOL"
    End If
    If OtherCHKB.Checked = True Then
        dsnewrow.Item("OTHER") = Me.OtherTXTB.Text
    ElseIf OtherCHKB.Checked = False Then
        dsnewrow.Item("OTHER") = "NEATOL"
    End If
    If AddedMissingDimCHKB.Checked = True Then
        dsnewrow.Item("ADDED MISSING DIMENSION") = Me.AddedMissingDimCHKB.Text
    ElseIf AddedMissingDimCHKB.Checked = False Then
        dsnewrow.Item("ADDED MISSING DIMENSION") = "NEATOL"
    End If
    If FixedDimensionCHKB.Checked = True Then
        dsnewrow.Item("FIXED DIMENSION") = Me.FixedDimensionCHKB.Text
    ElseIf FixedDimensionCHKB.Checked = False Then
        dsnewrow.Item("FIXED DIMENSION") = "NEATOL"
    End If
    ds.Tables("Counting").Rows.Add(dsnewrow)
    da.Update(ds, "Counting")
    MsgBox("Entry succesfully added to database.")
    MissedPartCHKB.Checked = False
    MissedAutomatedPartCHKB.Checked = False
    NotInEpicorCHKB.Checked = False
    NonStockCHKB.Checked = False
    MissedSTKItemCHKB.Checked = False
    MissedBuyoutCHKB.Checked = False
    MissedPrintsNOTSentChadCHKB.Checked = False
    MissingPrintAfterQTYCHKB.Checked = False
    AddedMissingDimCHKB.Checked = False
    FixedDimensionCHKB.Checked = False
    OtherCHKB.Checked = False
    OtherTXTB.Text = ""
             MonthList2021.SelectedItem = False
End Sub

Answer 1

Ok, you are close.

So, data adaptor - you want to give it a VALID sql - not JUST a table name.

sqlCommand builder - you declarer it - but it is connected and associated with NOTHING ELSE!!

So, you need this:

Dim con As New OleDb.OleDbConnection(My.Settings.TestDB)

So, you created connect object - but did not provide details of the connection. I suggest you create that connections in the settings - use the connection builder.

Dim da As OleDb.OleDbDataAdapter

You create this adaptor - but NEEDS a connection and MORE important, it ALSO needs some sql.

because we are ONLY going to add rows, lets give the adaptor a sql statement - but one that returns NO records - but we STILL need to fill out this adaptor.

So, use this:

Dim da As OleDb.OleDbDataAdapter("SELECT * from [Data Collection] WHERE ID = 0",con)

Next up, you create a command builder (this is good), but you left out it being connected or assocated with ANY thing else, so you need/want this:

Dim cb As New OleDbCommandBuilder()

Becomes this:

Dim cb As New OleDbCommandBuilder(da)

When you execute the above, then the insert, delete, update and select commands will be built for you (nice.!).

Now, to add a new data row?

After we done all above, then we need to load up our datatable (again, it just sitting there - not connected to anything). So, do this:

However, you have

Dim ds As New DataSet

No, we dont' need a "set" of tables - you need ONE table.

So change above to

dim ds as New DataTable

Now, lets fill (and more imporant) associate our table with our data connciton objects.

da.Fill(ds)

Now you CAN edit rows in ds (but we don't' have any.!!).

Now we can create a whole new separate row object (as you did), but I tend to just do this:

With ds.Rows.Add
   .item("Some Field Name") = "your value goes here"
   .etc .etc
End With

But, you can if you wish create a whole new seperate row. Again that row can't just be "all by itself" here.

So, you create the blank row this way:

        Dim myRow As DataRow = rstTable.Rows.Add

Or in your case: dsnewrow = ds.Rows.Add

After you add one row, or several?

Then you have to send back these new rows to the database.

 da.Update(ds)

Now note how I am using "ds", but it is a datatable and not a dataset. You "can" use a dataset - but really, you don't need one.

Also, last but not least?

Well, the adaptor, the reader, the connection object and the sql?

You can use ONE object that contains ALL 3 of the above. This will save your fingers, and also several variables.

So, I suggest this setup - since connection object, and sql, and sql command are ALL in one object.

So, this is the 'template' I use:

   Using cmdSQL As New OleDbCommand("SELECT * from tblHotels WHERE ID = 0",
                    New OleDbConnection(My.Settings.TestDB))

        Dim da As New OleDbDataAdapter(cmdSQL)
        Dim sqlBuild As New OleDbCommandBuilder(da)

        Dim rstTable As New DataTable
        da.Fill(rstTable)

        With rstTable.Rows.Add
            .Item("HotelName") = "The zoo Hotel."
        End With

        ' add one more row - but with  row var
        Dim MyOneRow As DataRow = rstTable.Rows.Add

        MyOneRow("HotelName") = "The Barn Hotel"
        MyOneRow("City") = "My City"

        ' write BOTH ROWS back to database - all data rows were AND ARE added to rstTable

        da.Update(rstTable)


    End Using

Edit - answers to comments question

What do you dimension cmdSQL as?

I have either this:

    Dim cmdSQL As New OleDbCommand
    or I have this
    Dim cmdSQL As OleDbCommand = New OleDbCommand

The both amount to the same thing. Note in some cases I used OleDb.OleDbCommand, and in SOME cases I used OleDBcommand (I left out the OleDB)

I am ABLE to save some fingers and typing and not have to use the OleDB. as a prefix because at the top of the module (before any code) I have this:

Imports System.Data.OleDb

If I leave above out, then I HAVE to use OleDb., but with the above imports then I am free to leave out the OleDB. (OleDB(dot) prefix).

>>Fill" is not a member of OleDbDataAdapter(),

It should be. I assume you do this:

    Using cmdSQL As OleDbCommand = New OleDbCommand("SELECT * from tblHotels WHERE ID = 0",
                    New OleDbConnection(My.Settings.TestDB))


        Dim da As New OleDbDataAdapter(cmdSQL)

Of course th above (declares) a cmdSQL object in the "using". You can't thus use cmdSQL outside of that using/end using block.

>>getting many errors associated with my variable "da"; BC3031 Value of type 'OleDbDataAdapter()' cannot be converted to 'OleDbDataAdapter'

You are declaring da as

Note how in above I do get/have "fill" as a method of da in this case.

Since you note that the last "using" example of mine works, then something is messed up in your code.

For example, you have this:

Private Sub ConnectionPrep(.............

Ok, but that code is 100% separate and 100% isolated from the 2nd routine where your code is. The 2nd routine can't see, nor use (nor does it) have anything to do with that 2nd posted routine.

So how, when, where do you use the first routine?

And there is LITTLE need to put that connection string setup in code.

Use the project settings for this.

Eg this page:

So, when you use the above connection builder? Then all of the provider and settings are now available ANYWHERE in code.

You can use

My.Settings.TestDB 

The above thus will return a valid working connection string - in this case for oleDB.