TabPage selection, move the Focus to the previous ActiveControl when a TabPage is reselected

Question

I need some help to focus a particular control when a TabPage is revisited. I followed many other blogs, but I wasn't able to solve the problem myself.

I created the TabPages inside a MDIForm:

Public Sub Tab_Open(Of T As {Form, New})(name As String, NameofTab As String, Tabnumber As String)

    Dim _formByName As New Dictionary(Of String, Form)
    Dim Frm As Form = Nothing

    If Not _formByName.TryGetValue(name, Frm) OrElse _formByName(name).IsDisposed Then
        Frm = New T()
        _formByName(name) = Frm
    End If

    Dim childTab As TabPage = New TabPage With {
        .Name = NameofTab & " : " & Tabnumber,
        .Text = NameofTab & " : " & Tabnumber,
        .Tag = Frm.Name
    }

    Form1.tabForms.TabPages.Add(childTab)

    Frm.TopLevel = False
    Frm.FormBorderStyle = FormBorderStyle.None
    Frm.Parent = Form1.tabForms.TabPages(Form1.tabForms.TabCount - 1)
    Frm.Dock = DockStyle.Fill
    Frm.Show()
   
    Form1.tabForms.SelectedTab = childTab
    Form1.tabForms.Visible = True
End Sub

Let's assume that in first TabPage the Focus was on a TextBox (with TabIndex = 4), now I may be click on the second TabPage.
After some calculations, when I select the previous TabPage, the Focus should be set to the TextBox with TabIndex = 4 again, but that's not happening.

I tried to create a Dictionary in the MDIForm as:

Public Tab_Last_Focus_info As New Dictionary(Of String, String())

and in SelectedIndexChanged I have this code:

 Private Sub tabForms_SelectedIndexChanged(sender As Object, e As EventArgs) Handles tabForms.SelectedIndexChanged

    If Tab_Last_Focus_info.ContainsKey(tabForms.SelectedTab.Name) Then
        Dim FullTypeName1 As String = String.Format("{0}", Tab_Last_Focus_info.Item(tabForms.SelectedTab.Name))
        Dim Indxval As String = String.Format("{1}", Tab_Last_Focus_info.Item(tabForms.SelectedTab.Name))

        Dim FullTypeName As String = Application.ProductName & "." & FullTypeName1
        Dim FormInstanceType As Type = Type.GetType(FullTypeName, True, True)
        Dim frm As Form = CType(Activator.CreateInstance(FormInstanceType), Form)
        Dim Focus_on As Integer = Integer.Parse(Indxval)

        frm.Controls(Focus_on).Focus()
        ' Not working too =>
        ' frm.Controls(Focus_on).Select() 

        ' Invisible or disabled control cannot be activated =>
        ' ActiveControl = frm.Controls(Focus_on) 'System.ArgumentException: 
    End If
End Sub

In the Form, which is opened via a Menu, I have this code for the Control that's focused:

Private Sub All_Got_Focus(sender As Object, e As EventArgs) Handles TB_ImageLoc.GotFocus, TB_CompWebsite.GotFocus,
    TB_CompPinCD.GotFocus, TB_CompPAN.GotFocus, TB_CompName.GotFocus, TB_CompMobile.GotFocus,
    TB_CompMD.GotFocus, TB_CompLL.GotFocus, TB_CompGSTIN.GotFocus, TB_CompFax.GotFocus, TB_CompEmail.GotFocus,
    TB_CompCD.GotFocus, TB_CompAreaCity.GotFocus, RTB_CompADD.GotFocus, PB_Logo.GotFocus, DTP_CompEst.GotFocus, DGV_CompList.GotFocus,
    CHKB_CompIsRegTrans.GotFocus, CB_CompStateID.GotFocus, CB_CompDistrictID.GotFocus, But_Upd.GotFocus, But_SelectLogo.GotFocus,
    But_Search.GotFocus, But_Reset.GotFocus, But_Refresh.GotFocus, But_GridSelect.GotFocus, But_Exit.GotFocus, But_Edit.GotFocus,
    But_Del.GotFocus, But_Add.GotFocus
   
    If Form1.Tab_Last_Focus_info.ContainsKey(Form1.tabForms.SelectedTab.Name) Then
        Form1.Tab_Last_Focus_info.Remove(Form1.tabForms.SelectedTab.Name)
    End If

    Form1.Tab_Last_Focus_info.Add(Form1.tabForms.SelectedTab.Name, New String() {Me.Name, Me.ActiveControl.TabIndex})
End Sub

Now in TabIndexChange I'm getting a correct value from the Dictionary, but I'm not able to focus on the required tab.

Kindly help and let me know what I am missing or what need to taken care for this issue or please let me know any other better idea for the same.

Answer 1

Finally I solved the issue after struggling for 8 Days :)

As I mentioned earlier I Open the forms as tabs using the Sub Tab_Open mentioned in the question.

Defined or created a new dictionary in MDI form as

Public tabPagesActiveControl As New Dictionary(Of String, Control)

and defined a control variable as

Dim Sel_Control As Control

Now in each form when the control is focused I have the below code to assign the current control alone to the dictionary:

Private Sub All_Focus(sender As Object, e As EventArgs) Handles TBox_Reg_website.GotFocus,
        TBox_Reg_To.GotFocus, TBox_Reg_State.GotFocus, TBox_Reg_PinCD.GotFocus, TBox_Reg_PAN.GotFocus, TBox_Reg_office_num.GotFocus,
        TBox_Reg_mobile_num.GotFocus, TBox_Reg_GSTIN.GotFocus, TBox_Reg_fax_no.GotFocus, TBox_Reg_email.GotFocus, TBox_Reg_country.GotFocus,
        TBox_Reg_Company.GotFocus, TBox_Reg_City.GotFocus, TBox_Reg_Add2.GotFocus, TBox_Reg_Add1.GotFocus, TB_Curr_website.GotFocus,
        TB_Curr_state.GotFocus, TB_Curr_RegTo.GotFocus, TB_Curr_Pincd.GotFocus, TB_Curr_Pan.GotFocus, TB_Curr_office_num.GotFocus,
        TB_Curr_Mobile_num.GotFocus, TB_Curr_Gstin.GotFocus, TB_Curr_fax_no.GotFocus, TB_Curr_email.GotFocus, TB_Curr_country.GotFocus,
        TB_Curr_Company.GotFocus, TB_Curr_city.GotFocus, TB_Curr_add2.GotFocus, TB_Curr_add1.GotFocus,
        PICBox_Reg_Logo.GotFocus, MSP_Reg.GotFocus, Label9.GotFocus, Label8.GotFocus, Label7.GotFocus, Label6.GotFocus, Label5.GotFocus,
        Label4.GotFocus, Label3.GotFocus, Label2.GotFocus, Label15.GotFocus, Label14.GotFocus, Label13.GotFocus, Label12.GotFocus,
        Label11.GotFocus, Label10.GotFocus, Label1.GotFocus,
        ChkBx_Upd_Logo.GotFocus, Chkbox_NoLogo.GotFocus

        If Form1.tabPagesActiveControl.ContainsKey(Form1.TabControl1.SelectedTab.Name) Then
            Form1.tabPagesActiveControl.Remove(Form1.TabControl1.SelectedTab.Name)
        End If

        Form1.tabPagesActiveControl.Add(Form1.TabControl1.SelectedTab.Name, Me.ActiveControl)

    End Sub

and in the MDI form when tab select index changes having the below code:

Private Sub TabControl1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles TabControl1.SelectedIndexChanged

        If tabPagesActiveControl.ContainsKey(Me.TabControl1.SelectedTab.Name) Then
            
            Sel_Control = tabPagesActiveControl.Item(Me.TabControl1.SelectedTab.Name)
            
            Sel_Control.Focus()
            
        End If

    End Sub

Thanks :)