How to make changes on one form that will change information on another form

[Srut]

I am trying to get column 6 in the data grid view to be subtracted by 1 when the save button is pressed. The problem is the data grid view of column 6 is on my book_table form and the save button that i will press to subtract 1 from the data grid view is on my transaction form.

I have written this bit of code but it does not seem to work. i created a variable called butclcik and set its return type as a boolean. (Public butclcik As Boolean) Then i made an instance of the Book table called boktble. (Dim boktble As Book_Table = New Book_Table) I then tried to subtract 1 from the datagridview column 6 like this

Double.Parse((boktble.Book_TableDataGridView.Columns(6).ValueType = boktble.Book_TableDataGridView.Columns(6).ValueType) - 1)

Dim boktble As Book_Table = New Book_Table
    Public butclcik As Boolean
    Private Sub SaveButton_Click(sender As Object, e As EventArgs) Handles SaveButton.Click
        butclcik = True
        Try
            If butclcik = True Then
                Double.Parse((boktble.Book_TableDataGridView.Columns(6).ValueType = boktble.Book_TableDataGridView.Columns(6).ValueType) - 1)
            End If
 
            Dim datatiercal As DataTier = New DataTier(Due_DateDateTimePicker.Value.Date, Return_DateDateTimePicker.Value.Date)
            CostTextBox.Text = String.Format("{0:c2}", datatiercal.finepreiceprocal)
            DayOverduetextbox.Text = datatiercal.Daysoverdueprocal
            Transaction_TableDataGridView.Columns(7).DefaultCellStyle.Format = "c"
            Me.Validate()
            Me.Transaction_TableBindingSource.EndEdit()
            Me.TableAdapterManager.UpdateAll(Me.LibrarymanagementDataSet2)
            CostTextBox.Text = String.Format("{0:c2}", datatiercal.finepreiceprocal)
            MsgBox("Transaction was saved")
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        End Try
    End Sub

This is all the code in my transaction form.

Public Class Transactions_Table
    Private Shared Instance As Transactions_Table
    Public Shared ReadOnly Property TransactionsTableInstance() As Transactions_Table
        Get
            If Instance Is Nothing Then
                Instance = New Transactions_Table
            End If
            Return Instance
        End Get
    End Property
    Private Sub Transaction_TableBindingNavigatorSaveItem_Click(sender As Object, e As EventArgs)
        Me.Validate()
        Me.Transaction_TableBindingSource.EndEdit()
        Me.TableAdapterManager.UpdateAll(Me.LibrarymanagementDataSet2)
 
    End Sub
 
    Private Sub Transactions_Table_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Me.Book_TableTableAdapter1.Fill(Me.LibrarymanagementDataSet2.Book_Table)
        'TODO: This line of code loads data into the 'LibrarymanagementDataSet2.Transaction_Table' table. You can move, or remove it, as needed.
        Me.Transaction_TableTableAdapter.Fill(Me.LibrarymanagementDataSet2.Transaction_Table)
    End Sub
 
 
    Dim boktble As Book_Table = New Book_Table
    Public butclcik As Boolean
    Private Sub SaveButton_Click(sender As Object, e As EventArgs) Handles SaveButton.Click
        butclcik = True
        Try
            If butclcik = True Then
                Double.Parse((boktble.Book_TableDataGridView.Columns(6).ValueType = boktble.Book_TableDataGridView.Columns(6).ValueType) - 1)
            End If
 
            Dim datatiercal As DataTier = New DataTier(Due_DateDateTimePicker.Value.Date, Return_DateDateTimePicker.Value.Date)
            CostTextBox.Text = String.Format("{0:c2}", datatiercal.finepreiceprocal)
            DayOverduetextbox.Text = datatiercal.Daysoverdueprocal
            Transaction_TableDataGridView.Columns(7).DefaultCellStyle.Format = "c"
            Me.Validate()
            Me.Transaction_TableBindingSource.EndEdit()
            Me.TableAdapterManager.UpdateAll(Me.LibrarymanagementDataSet2)
            CostTextBox.Text = String.Format("{0:c2}", datatiercal.finepreiceprocal)
            MsgBox("Transaction was saved")
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        End Try
    End Sub
 
    Private Sub Transactions_Table_FormClosing(sender As Object, e As FormClosingEventArgs) Handles MyBase.FormClosing
        Instance = Nothing
    End Sub
 
    Private Sub Transaction_TableBindingNavigatorSaveItem_Click_1(sender As Object, e As EventArgs) Handles Transaction_TableBindingNavigatorSaveItem.Click
        Me.Validate()
        Me.Transaction_TableBindingSource.EndEdit()
        Me.TableAdapterManager.UpdateAll(Me.LibrarymanagementDataSet2)
 
    End Sub
 
    Private Sub AddButton_Click(sender As Object, e As EventArgs) Handles AddButton.Click
        Try
            Dim datatiercal As DataTier = New DataTier(Due_DateDateTimePicker.Value.Date, Return_DateDateTimePicker.Value.Date)
            CostTextBox.Text = String.Format("{0:c2}", datatiercal.finepreiceprocal)
            Transaction_TableBindingSource.AddNew()
            DayOverduetextbox.Text = datatiercal.Daysoverdueprocal
            CostTextBox.Text = String.Format("{0:c2}", datatiercal.finepreiceprocal)
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        End Try
    End Sub
 
    Private Sub DeleteButton_Click(sender As Object, e As EventArgs) Handles DeleteButton.Click
        Try
            Dim result As Integer = MessageBox.Show("Are you sure you want to delete this Transaction", "Delete Transaction", MessageBoxButtons.YesNo)
            If result = DialogResult.No Then
                MessageBox.Show("Transaction was not deleted")
            ElseIf result = DialogResult.Yes Then
                Transaction_TableBindingSource.RemoveCurrent()
                MessageBox.Show("The Transaction was deleted")
            End If
 
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        End Try
    End Sub
 
    Private Sub UpdateButton_Click(sender As Object, e As EventArgs) Handles UpdateButton.Click
        Try
            Dim datatiercal As DataTier = New DataTier(Due_DateDateTimePicker.Value.Date, Return_DateDateTimePicker.Value.Date)
            CostTextBox.Text = String.Format("{0:c2}", datatiercal.finepreiceprocal)
            DayOverduetextbox.Text = datatiercal.Daysoverdueprocal
            Transaction_TableDataGridView.Columns(7).DefaultCellStyle.Format = "c"
            Me.Validate()
            Me.Transaction_TableBindingSource.EndEdit()
            Me.TableAdapterManager.UpdateAll(Me.LibrarymanagementDataSet2)
            CostTextBox.Text = String.Format("{0:c2}", datatiercal.finepreiceprocal)
            MsgBox("Transaction was Updated")
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        End Try
    End Sub
 
    Private Sub RenewButton_Click(sender As Object, e As EventArgs) Handles RenewButton.Click
        Try
            Due_DateDateTimePicker.Value = Due_DateDateTimePicker.Value.Date.AddDays(7)
            Return_DateDateTimePicker.Value = Due_DateDateTimePicker.Value.Date
            Dim datatiercal As DataTier = New DataTier(Due_DateDateTimePicker.Value.Date, Return_DateDateTimePicker.Value.Date)
            CostTextBox.Text = String.Format("{0:c2}", datatiercal.finepreiceprocal)
            DayOverduetextbox.Text = datatiercal.Daysoverdueprocal
            Transaction_TableDataGridView.Columns(7).DefaultCellStyle.Format = "c"
            Me.Validate()
            Me.Transaction_TableBindingSource.EndEdit()
            Me.TableAdapterManager.UpdateAll(Me.LibrarymanagementDataSet2)
            CostTextBox.Text = String.Format("{0:c2}", datatiercal.finepreiceprocal)
            MsgBox("The Book has Been Renews for a week")
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        End Try
    End Sub
 
    Private Sub FillByToolStripButton_Click(sender As Object, e As EventArgs)
        Try
            Me.Transaction_TableTableAdapter.FillBy(Me.LibrarymanagementDataSet2.Transaction_Table)
        Catch ex As System.Exception
            System.Windows.Forms.MessageBox.Show(ex.Message)
        End Try
 
    End Sub
 
    Private Sub IDToolStripButton_Click(sender As Object, e As EventArgs) Handles IDToolStripButton.Click
        Try
            Me.Transaction_TableTableAdapter.ID(Me.LibrarymanagementDataSet2.Transaction_Table, CType(Param1ToolStripTextBox.Text, Integer))
        Catch ex As System.Exception
            System.Windows.Forms.MessageBox.Show(ex.Message)
        End Try
 
    End Sub
 
 
    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Try
            Transaction_TableBindingSource.MovePrevious()
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try
    End Sub
 
    Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
        Try
            Transaction_TableBindingSource.MoveNext()
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try
    End Sub
End Class

[jmcilhinney]

Which forum creates and displays the other and how does it do it? I'm on a phone and there appears to be a lot of irrelevant code to look through to see whether you've included that.

[Srut]

I have a form called book management system which is a mdi container. from the book management form i can open the transaction _form and book_form. what i want to do is have the transaction form subtract a value from the data grid form on the Book_form. but the code i wrote to do this isn't working and i am unsure why.

[Srut]

Anyone else who reads this have any idea could use all the help i get

[wes4dbt]

This line has problems,

Double.Parse((boktble.Book_TableDataGridView.Columns(6).ValueType = boktble.Book_TableDataGridView.Columns(6).ValueType) - 1)

Your trying to subtract 1 from a dgv column ValueType, do you really want to change the columns value type?

It sounds like you want to change a value in the Books table after you have changed a value in the transaction table. If so, then work directly with the books table. then when you open the Books_Table form the value will already be correct.

[Srut]

i tired working with the book table directly but the butclick variable stay false when i check if the button was pressed. can you give me more detail about how to get it to work directly from the book_table

[wes4dbt]

i tired working with the book table directly but the butclick variable stay false when i check if the button was pressed. can you give me more detail about how to get it to work directly from the book_table

It's hard for me to even respond to this because it really doesn't make sense. At least not to me.
this code,

    Public butclcik As Boolean
    Private Sub SaveButton_Click(sender As Object, e As EventArgs) Handles SaveButton.Click
        butclcik = True
        Try
            If butclcik = True Then
                Double.Parse((boktble.Book_TableDataGridView.Columns(6).ValueType = boktble.Book_TableDataGridView.Columns(6).ValueType) - 1)
            End If

Doesn't make sense. butclcik is ALWAYS true when you click the Savebutton, it really doesn't serve any purpose.

I can't really help with working directly with the Book table without more information.

I am trying to get column 6 in the data grid view to be subtracted by 1 when the save button is pressed

I'm guessing that the dgv column 6 is bound to a field in the Book table. Are you saying you want to subtract 1 from the value in that field for EVERY row in that table? If so you can do that by manually cycling through the Me.LibrarymanagementDataSet2.Book_Table datatable using a For/Next loop or add an Update Query to the Book_TableTableAdapter in the LibrarymanagementDataSet2 dataset.

[Niya]

If you have an object on a Form, and you want to access that object from another Form, you must declare that object variable as a public variable, or use a public property to access the object if it's variable is private. It's no different to manipulating objects on any other class.

[jmcilhinney]

If you want one MDI child form to affect a change on another then the "proper" way is to do it without either knowing that the other exists. If child A is to make a change on child B then child A should raise an event, the parent form should handle that event and call a method of child B and then child B should make the change.

I'm guessing that you don't want to go that far though, so the options for child A getting direct access to child B are:

1. If child B is the default instance of it's type then child A can access it via the default instance.
2. Child A can use a loop or LINQ query to get a reference to child B from the MdiChildren collection of its MdiParent.
3. The parent form can pass a child B reference into child A.

You need to decide which way you want to go.

Once child A has a reference to child B, I would still very much suggest that child A simply calls a method and the actual change is made by child B to itself within that method.

[Srut]

It's hard for me to even respond to this because it really doesn't make sense. At least not to me.
this code,

    Public butclcik As Boolean
    Private Sub SaveButton_Click(sender As Object, e As EventArgs) Handles SaveButton.Click
        butclcik = True
        Try
            If butclcik = True Then
                Double.Parse((boktble.Book_TableDataGridView.Columns(6).ValueType = boktble.Book_TableDataGridView.Columns(6).ValueType) - 1)
            End If

Doesn't make sense. butclcik is ALWAYS true when you click the Savebutton, it really doesn't serve any purpose.

I can't really help with working directly with the Book table without more information.

I'm guessing that the dgv column 6 is bound to a field in the Book table. Are you saying you want to subtract 1 from the value in that field for EVERY row in that table? If so you can do that by manually cycling through the Me.LibrarymanagementDataSet2.Book_Table datatable using a For/Next loop or add an Update Query to the Book_TableTableAdapter in the LibrarymanagementDataSet2 dataset.

ok so i made a method in the book table called Copiescount()

Public Sub Copiescount()
        If Transactions_Table.butclcik = True Then
            CopiesTextBox.Text = Double.Parse((CopiesTextBox.Text = CopiesTextBox.Text) - 1)
            Me.TableAdapterManager.UpdateAll(Me.LibrarymanagementDataSet2)
            Me.Book_TableTableAdapter.Update(Me.LibrarymanagementDataSet2)
        End If
    End Sub

here i check to see if the butclcik is true in the transaction form before doing the calculations in the book form. when i check if the butclcik value is true it comes back correct so that part is fine. the problem is the calculation is not being made. p.s in changed it to the copiestextbox instead of the datagridview.

[Srut]

If you have an object on a Form, and you want to access that object from another Form, you must declare that object variable as a public variable, or use a public property to access the object if it's variable is private. It's no different to manipulating objects on any other class.

i did do this in the transaction table to get the value of butclcik in the Book_table and it works now thank you but the problem is getting the expression to make the subtraction from the values in the book_table after it checks if butclcik is true in the Transaction table.

Public Shared butclcik As Boolean
    Private Sub SaveButton_Click(sender As Object, e As EventArgs) Handles SaveButton.Click
        Try
            butclcik = True
 
 
            Dim datatiercal As DataTier = New DataTier(Due_DateDateTimePicker.Value.Date, Return_DateDateTimePicker.Value.Date)
            CostTextBox.Text = String.Format("{0:c2}", datatiercal.finepreiceprocal)
            DayOverduetextbox.Text = datatiercal.Daysoverdueprocal
            Transaction_TableDataGridView.Columns(7).DefaultCellStyle.Format = "c"
            Me.Validate()
            Me.Transaction_TableBindingSource.EndEdit()
            Me.Book_TableTableAdapter1.Update(Me.LibrarymanagementDataSet2)
            Me.TableAdapterManager.UpdateAll(Me.LibrarymanagementDataSet2)
            CostTextBox.Text = String.Format("{0:c2}", datatiercal.finepreiceprocal)
            MsgBox("Transaction was saved")
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        End Try
    End Sub

[Srut]

here is the book table where i am now working directly with as you guys suggested but the calculation are not being done

Public Class Book_Table
    Private Shared Instance As Book_Table
    Public Shared ReadOnly Property BoolTableInstance() As Book_Table
        Get
            If Instance Is Nothing Then
                Instance = New Book_Table()
            End If
            Return Instance
        End Get
    End Property
 
    Public Sub Copiescount()
        If Transactions_Table.butclcik = True Then
            CopiesTextBox.Text = Double.Parse((CopiesTextBox.Text = CopiesTextBox.Text) - 1)
            Me.TableAdapterManager.UpdateAll(Me.LibrarymanagementDataSet2)
            Me.Book_TableTableAdapter.Update(Me.LibrarymanagementDataSet2)
        End If
    End Sub
 
    Private Sub Book_TableBindingNavigatorSaveItem_Click(sender As Object, e As EventArgs) Handles Book_TableBindingNavigatorSaveItem.Click
        Me.Validate()
        Me.Book_TableBindingSource.EndEdit()
        Me.TableAdapterManager.UpdateAll(Me.LibrarymanagementDataSet2)
 
    End Sub
 
 
    Private Sub AddButton_Click(sender As Object, e As EventArgs) Handles AddButton.Click
        Try
            Book_TableBindingSource.AddNew()
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        End Try
    End Sub
 
    Private Sub SaveButton_Click(sender As Object, e As EventArgs) Handles SaveButton.Click
        Try
            Me.Validate()
            Me.Book_TableBindingSource.EndEdit()
            Me.TableAdapterManager.UpdateAll(Me.LibrarymanagementDataSet2)
            Book_NameTextBox.Select()
            MsgBox("Book Was Saved")
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        End Try
    End Sub
 
    Private Sub DeleteButton_Click(sender As Object, e As EventArgs) Handles DeleteButton.Click
        Try
            Dim result As Integer = MessageBox.Show("Are you sure you want to delete this Book", "Delete Book", MessageBoxButtons.YesNo)
            If result = DialogResult.No Then
                MessageBox.Show("Book was not deleted")
            ElseIf result = DialogResult.Yes Then
                Book_TableBindingSource.RemoveCurrent()
                MessageBox.Show("The Book was deleted")
            End If
 
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        End Try
 
    End Sub
 
    Private Sub Update_Book_Click(sender As Object, e As EventArgs) Handles Update_Book.Click
        Try
 
            Me.Validate()
            Me.Book_TableBindingSource.EndEdit()
            Me.TableAdapterManager.UpdateAll(Me.LibrarymanagementDataSet2)
            MsgBox("Book was updated")
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        End Try
 
    End Sub
 
    Private Sub Book_Table_FormClosing(sender As Object, e As FormClosingEventArgs) Handles MyBase.FormClosing
        Instance = Nothing
    End Sub
 
    Private Sub View_Books_Click(sender As Object, e As EventArgs) Handles View_Books.Click
        Dim ViewBooksub As ViewBook = ViewBook.ViewBookInstance
        ViewBooksub.Show()
        ViewBooksub.Focus()
    End Sub
 
    Private Sub Book_TableBindingNavigatorSaveItem_Click_1(sender As Object, e As EventArgs) Handles Book_TableBindingNavigatorSaveItem.Click
        Me.Validate()
        Me.Book_TableBindingSource.EndEdit()
        Me.TableAdapterManager.UpdateAll(Me.LibrarymanagementDataSet2)
 
    End Sub
 
    Private Sub Book_TableBindingNavigatorSaveItem_Click_2(sender As Object, e As EventArgs) Handles Book_TableBindingNavigatorSaveItem.Click
        Me.Validate()
        Me.Book_TableBindingSource.EndEdit()
        Me.TableAdapterManager.UpdateAll(Me.LibrarymanagementDataSet2)
 
    End Sub
 
    Private Sub Book_Table_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        'TODO: This line of code loads data into the 'LibrarymanagementDataSet2.Book_Table' table. You can move, or remove it, as needed.
        Me.Book_TableTableAdapter.Fill(Me.LibrarymanagementDataSet2.Book_Table)
        Validate()
        Book_TableBindingSource.EndEdit()
        TableAdapterManager.UpdateAll(Me.LibrarymanagementDataSet2)
    End Sub
 
    Private Sub Book_ID2ToolStripButton_Click(sender As Object, e As EventArgs) Handles Book_ID2ToolStripButton.Click
        Try
            Me.Book_TableTableAdapter.Book_ID2(Me.LibrarymanagementDataSet2.Book_Table, CType(Param1ToolStripTextBox.Text, Integer))
        Catch ex As System.Exception
            System.Windows.Forms.MessageBox.Show(ex.Message)
        End Try
 
    End Sub
 
    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Try
            Book_TableBindingNavigator.MovePreviousItem.PerformClick()
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try
    End Sub
 
 
 
    Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
        Try
            Book_TableBindingNavigator.MoveNextItem.PerformClick()
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try
    End Sub
 
    Private Sub CopiesTextBox_TextChanged(sender As Object, e As EventArgs) Handles CopiesTextBox.TextChanged
 
    End Sub
 
 
 
 
End Class

here is the transaction table.

Public Class Transactions_Table
    Private Shared Instance As Transactions_Table
    Public Shared ReadOnly Property TransactionsTableInstance() As Transactions_Table
        Get
            If Instance Is Nothing Then
                Instance = New Transactions_Table
            End If
            Return Instance
        End Get
    End Property
    Private Sub Transaction_TableBindingNavigatorSaveItem_Click(sender As Object, e As EventArgs)
        Me.Validate()
        Me.Transaction_TableBindingSource.EndEdit()
        Me.TableAdapterManager.UpdateAll(Me.LibrarymanagementDataSet2)
 
    End Sub
 
    Private Sub Transactions_Table_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Me.Book_TableTableAdapter1.Fill(Me.LibrarymanagementDataSet2.Book_Table)
        'TODO: This line of code loads data into the 'LibrarymanagementDataSet2.Transaction_Table' table. You can move, or remove it, as needed.
        Me.Transaction_TableTableAdapter.Fill(Me.LibrarymanagementDataSet2.Transaction_Table)
    End Sub
 
 
 
    Public Shared butclcik As Boolean
    Private Sub SaveButton_Click(sender As Object, e As EventArgs) Handles SaveButton.Click
        Try
            butclcik = True
 
 
            Dim datatiercal As DataTier = New DataTier(Due_DateDateTimePicker.Value.Date, Return_DateDateTimePicker.Value.Date)
            CostTextBox.Text = String.Format("{0:c2}", datatiercal.finepreiceprocal)
            DayOverduetextbox.Text = datatiercal.Daysoverdueprocal
            Transaction_TableDataGridView.Columns(7).DefaultCellStyle.Format = "c"
            Me.Validate()
            Me.Transaction_TableBindingSource.EndEdit()
            Me.Book_TableTableAdapter1.Update(Me.LibrarymanagementDataSet2)
            Me.TableAdapterManager.UpdateAll(Me.LibrarymanagementDataSet2)
            CostTextBox.Text = String.Format("{0:c2}", datatiercal.finepreiceprocal)
            MsgBox("Transaction was saved")
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        End Try
    End Sub

[Srut]

It's hard for me to even respond to this because it really doesn't make sense. At least not to me.
this code,

    Public butclcik As Boolean
    Private Sub SaveButton_Click(sender As Object, e As EventArgs) Handles SaveButton.Click
        butclcik = True
        Try
            If butclcik = True Then
                Double.Parse((boktble.Book_TableDataGridView.Columns(6).ValueType = boktble.Book_TableDataGridView.Columns(6).ValueType) - 1)
            End If

Doesn't make sense. butclcik is ALWAYS true when you click the Savebutton, it really doesn't serve any purpose.

I can't really help with working directly with the Book table without more information.

I'm guessing that the dgv column 6 is bound to a field in the Book table. Are you saying you want to subtract 1 from the value in that field for EVERY row in that table? If so you can do that by manually cycling through the Me.LibrarymanagementDataSet2.Book_Table datatable using a For/Next loop or add an Update Query to the Book_TableTableAdapter in the LibrarymanagementDataSet2 dataset.

?
ok i just read what you wrote completely if i make an update query and display this as a datagridview it will place the updated information for the number of copies after i have made a transaction in my transaction table?

[Srut]

It's hard for me to even respond to this because it really doesn't make sense. At least not to me.
this code,

    Public butclcik As Boolean
    Private Sub SaveButton_Click(sender As Object, e As EventArgs) Handles SaveButton.Click
        butclcik = True
        Try
            If butclcik = True Then
                Double.Parse((boktble.Book_TableDataGridView.Columns(6).ValueType = boktble.Book_TableDataGridView.Columns(6).ValueType) - 1)
            End If

Doesn't make sense. butclcik is ALWAYS true when you click the Savebutton, it really doesn't serve any purpose.

I can't really help with working directly with the Book table without more information.

I'm guessing that the dgv column 6 is bound to a field in the Book table. Are you saying you want to subtract 1 from the value in that field for EVERY row in that table? If so you can do that by manually cycling through the Me.LibrarymanagementDataSet2.Book_Table datatable using a For/Next loop or add an Update Query to the Book_TableTableAdapter in the LibrarymanagementDataSet2 dataset.

how would i go about subtracting 1 from the copies in the book table after i make a transaction in the transaction table and click save. i thought after i click save in the transaction table and make butclick true then it would preform the expression to subtract 1 from copies in the book table after it checks if butclcik is true. but you are telling me after i click it and butclick will alsway be true so i cant use it this way. how would i go about make it so every time i click save in the transaction table the expression to subtract 1 from copies is done in the book table.

[wes4dbt]

Here's an example, you will have to change the names to work with your system.

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click

        Dim row As DataRow = Me.BooksDBDataSet.Books.FindByBookId(3)
        If Not row Is Nothing Then
            row("copies") = CInt(row("copies")) - 1
            Me.BooksTableAdapter.Update(Me.BooksDBDataSet.Books)
        End If
    End Sub

You will have to replace Me.BooksDBDataSet.Books.FindByBookId(3) the "3" with the current BookId value in the transaction table.