quick question for any one reading this

quick question for any one reading this

i have main mdi parant with a function on it , which needs to access the value of a textbox on a child form so i added the form to a module and when i code to acess the form i get all the parameters fine, but when i run the app i get an error message saying "object reference not set not set to an instance of the object"

i normally access forms in this way but ive never actully accessed a child from a parant but i cant see if being that difficult

no code?

mdiparant code
==================
'function to control mdi forms
Public Sub ShowSingleInstance(ByVal childType As Type)
For Each child As Form In Me.MdiChildren
If child.GetType Is childType Then
child.Activate() 'already loaded so bring to foreground
Return
End If
Next
Dim frm As Form = Activator.CreateInstance(childType) 'not loaded yet so create
frm.MdiParent = Me
frm.Show()
End Sub
========= function that controls mdi childs
========= function that controls thr clicks on the toolbar

Private Sub toolbar1_ButtonClick(ByVal sender As System.Object, ByVal e As System.Windows.Forms.ToolBarButtonClickEventArgs) Handles ToolBar1.ButtonClick
Select Case ToolBar1.Buttons.IndexOf(e.Button)
Case 0
frmCustomer_Add.DoDataSave("Customer_Add")
Case 1
Case 2
Case 4
Case 6
Case 7
Case 8
Case 10
Case 12
Case 13
Case 14
End Select
End Sub
================================
case 0 the first button frmCustomer_ADD. is defined in my module

Public frmCustomer_Add As New Customer_Add

if i define the form as NEW then i dont get the error however i cant seem to pick up any text from the text boxes on the form
on my child form i have a button calling the same function and it works fine, so it looks like the toolbar button is getting confused

Where's the code for DoDataSave.

Public Function DoDataSave(ByVal ChildName As String)
Try
MsgBox(ChildName)
Dim Cmd As OleDbCommand = New OleDbCommand
Cmd.CommandType = CommandType.StoredProcedure
Cmd.Connection = MyConnection

Select Case LCase(ChildName)
Case LCase("Customer_Add")
MsgBox(frmCustomer_Add.txtFullName.Text & " here")
With Cmd
.CommandText = "InsNewCustomer"
.Parameters.Add("@FullName", frmCustomer_Add.txtFullName.Text)
.Parameters.Add("@Building", frmCustomer_Add.txtBuilding.Text)
.Parameters.Add("@Street", frmCustomer_Add.txtStreet.Text)
.Parameters.Add("@Street2", frmCustomer_Add.txtStreet2.Text)
.Parameters.Add("@Town", frmCustomer_Add.txtTown.Text)
.Parameters.Add("@County", frmCustomer_Add.txtCounty.Text)
.Parameters.Add("@Postcode", frmCustomer_Add.txtPostCode.Text)
.Parameters.Add("@Country", 1)
.Parameters.Add("@Company", frmCustomer_Add.txtCompany.Text)
.Parameters.Add("@vat", frmCustomer_Add.txtVatNumber.Text)

.Parameters.Add("@Tel", "")
.Parameters.Add("@Fax", "")
.Parameters.Add("@FirstEmail", "")
.Parameters.Add("@SecondEmail", "")
.Parameters.Add("@Mobile", "")
.Parameters.Add("@BillingAddress", 1)

End With
Case Else
MsgBox("No data matching this command")
End Select

MyConnection.Open()
Cmd.ExecuteNonQuery()
MyConnection.Close()
MsgBox("saved")
Catch er As Exception
MsgBox(er.ToString)
Finally
MyConnection.Close()
End Try
End Function

You can break out the ShowSingleInstance method into two. One that returns the single instance and one that shows it.

VB Code:

'function to return mdi child
    Public Function GetSingleInstance(ByVal childType As Type) As Form
        For Each child As Form In Me.MdiChildren
            If child.GetType Is childType Then
                Return child 'already loaded so return
            End If
        Next
        Dim frm As Form = Activator.CreateInstance(childType) 'not loaded yet so create
        Return frm
    End Function
 
    'function to show mdi forms
    Public Sub ShowSingleInstance(ByVal childType As Type)
        Dim child As Form = GetSingleInstance(childType)
        'make sure everything is set
        If child.MdiParent Is Nothing Then child.MdiParent = Me
        'didn't test the part below but it should work
        If Not child.Visible Then
            child.Show()
        Else
            child.Activate()
        End If
    End Sub
 
        'syntax for use
        Dim frm As Form1 = GetSingleInstance(GetType(Form1))
        'if you have option strict on use this
        'Dim frm As Form1 = CType(GetSingleInstance(GetType(Form1)), Form1)
        MsgBox(frm.TextBox1.Text)

VB Code:

Public Function DoDataSave(ByVal ChildName As String)
Try
MsgBox(ChildName)
Dim Cmd As OleDbCommand = New OleDbCommand
Cmd.CommandType = CommandType.StoredProcedure
Cmd.Connection = MyConnection
 
Select Case LCase(ChildName)
Case LCase("Customer_Add")
Dim frm As frmCustomer_Add=GetSingleInstance(gettype(frmCustomer_Add))
MsgBox(frm.txtFullName.Text & " here")
With Cmd
.CommandText = "InsNewCustomer"
.Parameters.Add("@FullName", frm.txtFullName.Text)
.Parameters.Add("@Building", frm.txtBuilding.Text)
.Parameters.Add("@Street", frm.txtStreet.Text)
.Parameters.Add("@Street2", frm.txtStreet2.Text)
.Parameters.Add("@Town", frm.txtTown.Text)
.Parameters.Add("@County", frm.txtCounty.Text)
.Parameters.Add("@Postcode", frm.txtPostCode.Text)
.Parameters.Add("@Country", 1)
.Parameters.Add("@Company", frm.txtCompany.Text)
.Parameters.Add("@vat", frm.txtVatNumber.Text)
 
.Parameters.Add("@Tel", "")
.Parameters.Add("@Fax", "")
.Parameters.Add("@FirstEmail", "")
.Parameters.Add("@SecondEmail", "")
.Parameters.Add("@Mobile", "")
.Parameters.Add("@BillingAddress", 1)
 
End With
Case Else
MsgBox("No data matching this command")
End Select
 
MyConnection.Open()
Cmd.ExecuteNonQuery()
MyConnection.Close()
MsgBox("saved")
Catch er As Exception
MsgBox(er.ToString)
Finally
MyConnection.Close()
End Try
End Function