Question

So – I have a MySQL db with one employee table, using Devart Linq to SQL (for MySQL)
It has a primary key in the DataContext,
I can load the gridview,
select a row,
set an instance of Staff = to the ID and Name or the row selected in the gridview
set a Textbox = to Name of Staff
change the textbox and set the object Staff.Name to the textbox…..

but I cant submit the change back to the db!!!! Probably a stupid thing I’m doing as a newbie.

Public Class Form1

    Dim db As New MydbContext.MydbDataContext
    Dim bs = New BindingSource
    Dim Staff As New MydbContext.Employee

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

        ' load employee data from MySQL db in datagrid

        Dim StaffQuery = From s In db.Employees Select s
        bs.DataSource = StaffQuery
        DataGridView1.DataSource = bs

        ' this works fine

    End Sub

    Private Sub DataGridView1_CellClick(ByVal sender As System.Object, ByVal e As System.Windows.Forms.DataGridViewCellEventArgs) Handles DataGridView1.CellClick

        'create an instance of the object Staff with the ID and Name from the datagrid
        'is there a better way to do this?

        Staff.EmployeeID = DataGridView1.Rows(e.RowIndex).Cells("EmployeeID").Value
        Staff.Name = DataGridView1.Rows(e.RowIndex).Cells("Name").Value
        MsgBox(Staff.EmployeeID & " " & Staff.Name)
        TextBox1.Text = Staff.Name

        'this works fine

    End Sub

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

        Staff.Name = TextBox1.Text   'edit the Name
        MsgBox(Staff.EmployeeID & " " & Staff.Name)  ' this works - shows new Staff.Name from textbox
        db.SubmitChanges()   ' this fails to make db changes

    End Sub

End Class

Answer 1

I believe you need to add db.Staffs.InsertOnSubmit(Staff)

Where Staffs is the name of the collection of Staff objects.

However, rather than keep the context and object around all the time, why not just create the new Staff object when the user presses the save button?

Finally, you can call GetChangeSet() on your db context to see what changes are pending. This can help you understand when something strange happens.