simple question - Form progression

[Lil Ms Squirrel]

This code was taken from a forms collection that I use to create multiple instances of a form. For example, the application allows several customer records to be opened at once, but only one instance of every customer. So the full version has a method that allows you to check the object stored in each form's tag property.

When I open a customer record, I store the datarow from the dataset (or you could store just the customer's id) in the tag property. Then, I have a method in the forms collection called IsInstanceInCollection which goes something like this:

Public Function IsInstanceInCollection(ByVal formName As String, ByVal row As DataRow) As Form
        Dim item As Form
        Dim formRow As DataRow
        Dim counter As Integer
        Try
            'loop through the forms collection
            For Each item In list
                If item.Name.ToLower = formName.ToLower Then
                    'if the form names match then retrieve the row
                    formRow = CType(item.Tag, DataRow)
                    'if the items in the left most columns match then return the form as the correct item
                    If formRow(0) = row(0) Then
                        Return item
                    End If
                End If
            Next
        Catch ex As Exception
            MessageBox.Show("Error locating the specified instance of " & formName)
            Return Nothing
        Finally
            formRow = Nothing
            item = Nothing
        End Try
    End Function

This returns the instance of the form if found.

The calling code is an If statement that checks to see if the method returns something and if not, will create a new instance to display to the user and stores the relevant data row in the tag property as the new form is loaded.

It is overloaded to work in a variety of different ways.

A cut down version of this to work with the code that staticbob wrote would go something like this:

Public Sub Remove(ByVal formTagObject As Object)
        Dim frm As Form
        For Each frm In MyBase.InnerList
            If frm.Tag = formTagObject Then
                MyBase.InnerList.Remove(frm)
                Exit For
            End If
        Next
    End Sub

To use this, I just created a unique string to store in each new form's tag object when instantiating and adding them to the collection.

Hope this clarifies things