save treeview state and call from another form

  • Thread starter Thread starter Co
  • Start date Start date
C

Co

Hi All,

As a follow up of my previous question concerning calling functions
from another form I created this:

Public Class TreeViewState
Inherits Explorer1
Private tt As New Dictionary(Of String, Boolean)

Public Sub RestoreTreeViewExpandedState()

Dim i As Integer
For i = 0 To TreeView.Nodes.Count - 1

If tt.ContainsKey(TreeView.Nodes(i).Name) Then

If tt(TreeView.Nodes(i).Name) Then
TreeView.Nodes(i).Expand()
Else
TreeView.Nodes(i).Collapse()
End If
End If
Next
End Sub

Public Function SaveTreeState()

Dim i As Integer

For i = 0 To TreeView.Nodes.Count - 1

If TreeView.Nodes(i).Nodes.Count > 0 Then
tt.Add(TreeView.Nodes(i).Name, TreeView.Nodes
(i).IsExpanded)
End If
Next

Return tt
End Function

End Class

This class will save the status of the treeview on form Explorer1.
I want to call the functions in this class from another form,
frmZoeken:

Dim currentState As TreeViewState
currentState.SaveTreeState()
SaveQueryInTreeview()
currentUser.RestoreTreeViewExpandedState()

I get an error when I try this obect reference not set to an instance
of an object

Marco.
 
Hi All,

As a follow up of my previous question concerning calling functions
from another form I created this:

Public Class TreeViewState
Inherits Explorer1
Private tt As New Dictionary(Of String, Boolean)

Public Sub RestoreTreeViewExpandedState()

Dim i As Integer
For i = 0 To TreeView.Nodes.Count - 1

If tt.ContainsKey(TreeView.Nodes(i).Name) Then

If tt(TreeView.Nodes(i).Name) Then
TreeView.Nodes(i).Expand()
Else
TreeView.Nodes(i).Collapse()
End If
End If
Next
End Sub

Public Function SaveTreeState()

Dim i As Integer

For i = 0 To TreeView.Nodes.Count - 1

If TreeView.Nodes(i).Nodes.Count > 0 Then
tt.Add(TreeView.Nodes(i).Name, TreeView.Nodes
(i).IsExpanded)
End If
Next

Return tt
End Function

End Class

This class will save the status of the treeview on form Explorer1.
I want to call the functions in this class from another form,
frmZoeken:

Dim currentState As TreeViewState
currentState.SaveTreeState()
SaveQueryInTreeview()
currentUser.RestoreTreeViewExpandedState()

I get an error when I try this obect reference not set to an instance
of an object

Marco.
Click to expand...

This is exactly the same problem you had yesterday or the day before.
You are creating a variable (currentState) but not setting it to an
object. Also, again you are telling us about an error but not telling
us on which line the error occurs.

Any of these will create a new object:
Dim currentState As New TreeViewState

Dim currentState As TreeViewState = New TreeViewState

Dim currentState As TreeViewState
currentState = New TreeViewState

I don't like the fact that in this class you keep referring to an
object called "TreeView". It would be better if you added a parameter
to the New() of the TreeViewState class which is a reference to the
TreeView the class is to operate on. That way you could use this
class for any TreeView object.
 
Hi All,

As a follow up of my previous question concerning calling functions
from another form I created this:

Public Class TreeViewState
Inherits Explorer1
Private tt As New Dictionary(Of String, Boolean)

Public Sub RestoreTreeViewExpandedState()

Dim i As Integer
For i = 0 To TreeView.Nodes.Count - 1

If tt.ContainsKey(TreeView.Nodes(i).Name) Then

If tt(TreeView.Nodes(i).Name) Then
TreeView.Nodes(i).Expand()
Else
TreeView.Nodes(i).Collapse()
End If
End If
Next
End Sub

Public Function SaveTreeState()

Dim i As Integer

For i = 0 To TreeView.Nodes.Count - 1

If TreeView.Nodes(i).Nodes.Count > 0 Then
tt.Add(TreeView.Nodes(i).Name, TreeView.Nodes
(i).IsExpanded)
End If
Next

Return tt
End Function

End Class

This class will save the status of the treeview on form Explorer1.
I want to call the functions in this class from another form,
frmZoeken:

Dim currentState As TreeViewState
currentState.SaveTreeState()
SaveQueryInTreeview()
currentUser.RestoreTreeViewExpandedState()

I get an error when I try this obect reference not set to an instance
of an object

Marco.
Click to expand...

This is exactly the same problem you had yesterday or the day before.
You are creating a variable (currentState) but not setting it to an
object. Also, again you are telling us about an error but not telling
us on which line the error occurs.

Any of these will create a new object:
Dim currentState As New TreeViewState

Dim currentState As TreeViewState = New TreeViewState

Dim currentState As TreeViewState
currentState = New TreeViewState

I don't like the fact that in this class you keep referring to an
object called "TreeView". It would be better if you added a parameter
to the New() of the TreeViewState class which is a reference to the
TreeView the class is to operate on. That way you could use this
class for any TreeView object.
 
This is exactly the same problem you had yesterday or the day before.
You are creating a variable (currentState) but not setting it to an
object.  Also, again you are telling us about an error but not telling
us on which line the error occurs.

Any of these will create a new object:
        Dim currentState As New TreeViewState

        Dim currentState As TreeViewState = New TreeViewState

        Dim currentState As TreeViewState
        currentState = New TreeViewState

I don't like the fact that in this class you keep referring to an
object called "TreeView".  It would be better if you added a parameter
to the New() of the TreeViewState class which is a reference to the
TreeView the class is to operate on.  That way you could use this
class for any TreeView object.
Click to expand...

Jack,

could you please show me how this Sub New()
would look like and tell me how I can create a New object
for a Treeview which is shown on my Explorer1 form?

You know what I don't understand is why you just can't call
something which is already there. Why creating a new instance?
I mean when I create a new instance I will use that newly created
object
instead of the one already on Explorer1 form.

Marco
 
This is exactly the same problem you had yesterday or the day before.
You are creating a variable (currentState) but not setting it to an
object.  Also, again you are telling us about an error but not telling
us on which line the error occurs.

Any of these will create a new object:
        Dim currentState As New TreeViewState

        Dim currentState As TreeViewState = New TreeViewState

        Dim currentState As TreeViewState
        currentState = New TreeViewState

I don't like the fact that in this class you keep referring to an
object called "TreeView".  It would be better if you added a parameter
to the New() of the TreeViewState class which is a reference to the
TreeView the class is to operate on.  That way you could use this
class for any TreeView object.
Click to expand...

Jack,

could you please show me how this Sub New()
would look like and tell me how I can create a New object
for a Treeview which is shown on my Explorer1 form?

You know what I don't understand is why you just can't call
something which is already there. Why creating a new instance?
I mean when I create a new instance I will use that newly created
object
instead of the one already on Explorer1 form.

Marco
 
I presume that you have used the debugger to prove that the code in LoadTree
is being executed and that the new data is being included in the query and
is appearing in the dt.Rows.Add line and you can see it in dt when the
AddNodes method is executed. If not, then that is what you need to confirm.

If the new data is in dt and if the Select is returning the correct result
then your problem is that the line
AddNodes(TreeView.Nodes, dt.Select("ISNULL(IDParent, -1) =-1"))

is updating the wrong instance of a TreeView, and this comes back to the
core of your issues. It seems that you may not have a clear understanding
of the distinction between classes, instances of a class, and a variables.
In particular, that variables are not the same as a class instance, that
more than one variable can refer to the same class instance, that the
instance which a variable refers to can be changed, and that a variable may
refer to no instance. As an example, you are talking about creating an
object when I think you are actually wanting to create a reference to an
object - two very different things.

The debugging you need to do will probably come down to proving that the
AddNodes is insertng the data into the correct instance of your TreeView.

This is exactly the same problem you had yesterday or the day before.
You are creating a variable (currentState) but not setting it to an
object. Also, again you are telling us about an error but not telling
us on which line the error occurs.

Any of these will create a new object:
Dim currentState As New TreeViewState

Dim currentState As TreeViewState = New TreeViewState

Dim currentState As TreeViewState
currentState = New TreeViewState

I don't like the fact that in this class you keep referring to an
object called "TreeView". It would be better if you added a parameter
to the New() of the TreeViewState class which is a reference to the
TreeView the class is to operate on. That way you could use this
class for any TreeView object.
Click to expand...

Jack,

could you please show me how this Sub New()
would look like and tell me how I can create a New object
for a Treeview which is shown on my Explorer1 form?

You know what I don't understand is why you just can't call
something which is already there. Why creating a new instance?
I mean when I create a new instance I will use that newly created
object
instead of the one already on Explorer1 form.

Marco
 
I presume that you have used the debugger to prove that the code in LoadTree
is being executed and that the new data is being included in the query and
is appearing in the dt.Rows.Add line and you can see it in dt when the
AddNodes method is executed. If not, then that is what you need to confirm.

If the new data is in dt and if the Select is returning the correct result
then your problem is that the line
AddNodes(TreeView.Nodes, dt.Select("ISNULL(IDParent, -1) =-1"))

is updating the wrong instance of a TreeView, and this comes back to the
core of your issues. It seems that you may not have a clear understanding
of the distinction between classes, instances of a class, and a variables.
In particular, that variables are not the same as a class instance, that
more than one variable can refer to the same class instance, that the
instance which a variable refers to can be changed, and that a variable may
refer to no instance. As an example, you are talking about creating an
object when I think you are actually wanting to create a reference to an
object - two very different things.

The debugging you need to do will probably come down to proving that the
AddNodes is insertng the data into the correct instance of your TreeView.

This is exactly the same problem you had yesterday or the day before.
You are creating a variable (currentState) but not setting it to an
object. Also, again you are telling us about an error but not telling
us on which line the error occurs.

Any of these will create a new object:
Dim currentState As New TreeViewState

Dim currentState As TreeViewState = New TreeViewState

Dim currentState As TreeViewState
currentState = New TreeViewState

I don't like the fact that in this class you keep referring to an
object called "TreeView". It would be better if you added a parameter
to the New() of the TreeViewState class which is a reference to the
TreeView the class is to operate on. That way you could use this
class for any TreeView object.
Click to expand...

Jack,

could you please show me how this Sub New()
would look like and tell me how I can create a New object
for a Treeview which is shown on my Explorer1 form?

You know what I don't understand is why you just can't call
something which is already there. Why creating a new instance?
I mean when I create a new instance I will use that newly created
object
instead of the one already on Explorer1 form.

Marco
 
Jack,

could you please show me how this Sub New()
would look like and tell me how I can create a New object
for a Treeview which is shown on my Explorer1 form?

You know what I don't understand is why you just can't call
something which is already there. Why creating a new instance?
I mean when I create a new instance I will use that newly created
object
instead of the one already on Explorer1 form.

Marco
Click to expand...

If you already have an object, you use that object, you don't create a
new one. I never said you should create a New Treeview. As I showed
you in my previous message, the problem was with TreeViewState. You
never initialized the currentState variable. You either need to set
it to an existing TreeViewState object, or you need to create a new
one.
 
Jack,

could you please show me how this Sub New()
would look like and tell me how I can create a New object
for a Treeview which is shown on my Explorer1 form?

You know what I don't understand is why you just can't call
something which is already there. Why creating a new instance?
I mean when I create a new instance I will use that newly created
object
instead of the one already on Explorer1 form.

Marco
Click to expand...

If you already have an object, you use that object, you don't create a
new one. I never said you should create a New Treeview. As I showed
you in my previous message, the problem was with TreeViewState. You
never initialized the currentState variable. You either need to set
it to an existing TreeViewState object, or you need to create a new
one.
 
If you already have an object, you use that object, you don't create a
new one.  I never said you should create a New Treeview.  As I showed
you in my previous message, the problem was with TreeViewState.  You
never initialized the currentState variable.  You either need to set
it to an existing TreeViewState object, or you need to create a new
one.- Tekst uit oorspronkelijk bericht niet weergeven -

- Tekst uit oorspronkelijk bericht weergeven -
Click to expand...

Jack,

If I understand correctly I must create a reference to the
Treeview object. Which doesn't mean I'm creating a new Treeview.
I will still use the Treeview on the Explorer1 form.

The examples you gave me create a new object:

Dim currentState As New TreeViewState
Dim currentState As TreeViewState = New TreeViewState
Dim currentState As TreeViewState
currentState = New TreeViewState

Is that creating the reference I need?
Also what would the Sub New() look like?

Marco
 
If you already have an object, you use that object, you don't create a
new one.  I never said you should create a New Treeview.  As I showed
you in my previous message, the problem was with TreeViewState.  You
never initialized the currentState variable.  You either need to set
it to an existing TreeViewState object, or you need to create a new
one.- Tekst uit oorspronkelijk bericht niet weergeven -

- Tekst uit oorspronkelijk bericht weergeven -
Click to expand...

Jack,

If I understand correctly I must create a reference to the
Treeview object. Which doesn't mean I'm creating a new Treeview.
I will still use the Treeview on the Explorer1 form.

The examples you gave me create a new object:

Dim currentState As New TreeViewState
Dim currentState As TreeViewState = New TreeViewState
Dim currentState As TreeViewState
currentState = New TreeViewState

Is that creating the reference I need?
Also what would the Sub New() look like?

Marco
 
Co said:
Jack,

If I understand correctly I must create a reference to the
Treeview object. Which doesn't mean I'm creating a new Treeview.
I will still use the Treeview on the Explorer1 form.

The examples you gave me create a new object:

Dim currentState As New TreeViewState
Dim currentState As TreeViewState = New TreeViewState
Dim currentState As TreeViewState
currentState = New TreeViewState

Is that creating the reference I need?
Also what would the Sub New() look like?

Marco
Click to expand...

http://msdn.microsoft.com/en-us/library/2x7h1hfk.aspx


Armin
 
Co said:
Jack,

If I understand correctly I must create a reference to the
Treeview object. Which doesn't mean I'm creating a new Treeview.
I will still use the Treeview on the Explorer1 form.

The examples you gave me create a new object:

Dim currentState As New TreeViewState
Dim currentState As TreeViewState = New TreeViewState
Dim currentState As TreeViewState
currentState = New TreeViewState

Is that creating the reference I need?
Also what would the Sub New() look like?

Marco
Click to expand...

http://msdn.microsoft.com/en-us/library/2x7h1hfk.aspx


Armin
 
Jack,

If I understand correctly I must create a reference to the
Treeview object. Which doesn't mean I'm creating a new Treeview.
I will still use the Treeview on the Explorer1 form.

The examples you gave me create a new object:

Dim currentState As New TreeViewState
Dim currentState As TreeViewState = New TreeViewState
Dim currentState As TreeViewState
currentState = New TreeViewState

Is that creating the reference I need?
Also what would the Sub New() look like?

Marco
Click to expand...

That creates a new instance of TreeViewState. I guess I don't know
what TreeViewState is. I thought it was a stand-alone class, but now
I guess maybe it is not. I see that it inherits from Explorer1, which
apparently is a form. I don't understand why you would want to do
that.

I think you need to do some serious studying on how to use classes and
objects.
 
Jack,

If I understand correctly I must create a reference to the
Treeview object. Which doesn't mean I'm creating a new Treeview.
I will still use the Treeview on the Explorer1 form.

The examples you gave me create a new object:

Dim currentState As New TreeViewState
Dim currentState As TreeViewState = New TreeViewState
Dim currentState As TreeViewState
currentState = New TreeViewState

Is that creating the reference I need?
Also what would the Sub New() look like?

Marco
Click to expand...

That creates a new instance of TreeViewState. I guess I don't know
what TreeViewState is. I thought it was a stand-alone class, but now
I guess maybe it is not. I see that it inherits from Explorer1, which
apparently is a form. I don't understand why you would want to do
that.

I think you need to do some serious studying on how to use classes and
objects.
 
That creates a new instance of TreeViewState.  I guess I don't know
what TreeViewState is.  I thought it was a stand-alone class, but now
I guess maybe it is not.  I see that it inherits from Explorer1, which
apparently is a form.  I don't understand why you would want to do
that.

I think you need to do some serious studying on how to use classes and
objects.
Click to expand...

Thank you
 
That creates a new instance of TreeViewState.  I guess I don't know
what TreeViewState is.  I thought it was a stand-alone class, but now
I guess maybe it is not.  I see that it inherits from Explorer1, which
apparently is a form.  I don't understand why you would want to do
that.

I think you need to do some serious studying on how to use classes and
objects.
Click to expand...

Thank you
 
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