Wonder if someone can help me out here as I'm not making any progress with
this...
I have an application which uses an MDI window. When it is running, the
application creates an instance of a COM object, passes into it an instance
of a local .NET class from my application, and then calls a method of the
COM object.
The COM object uses a method (ShowInfoForm) in the provided .NET object to
display an information form within the MDI container. The ShowInfoForm
function itself calls a method on my MDI form (GetInfoForm) which actually
creates and displays the information form.
\\\ In my MDI form
'The GetInfoForm function opens and returns a new
'instance of the InfoForm
Public Function GetInfoForm() As InfoForm
Dim f As New InfoForm
f.MdiParent = Me
f.Show()
Return f
End Function
///
However, when the .NET class method is called from within the COM object, it
is running in a different thread to that of my main application (for reasons
I don't understand). This therefore leads to an error when my
MDI.GetInfoForm method tries to set the .MdiParent property of the
information form:
A first chance exception of type 'System.Argumen tException' occurred in
system.windows. forms.dll
Additional information: Controls created on one thread cannot be
parented
to a control on a different thread.
When I've had threading issues with forms before, I've always used the
Invoke method on the form to execute the code in the form's own thread. I
tried to do that here by using the following code:
\\\ In my .NET class:
'Create a delegate for the InfoForm function.
Public Delegate Function GetInfoForm_Del egate() As InfoForm
Public Function ShowInfoForm
Dim inf As InfoForm
Dim getInfoDelegate As GetInfoForm_Del egate
'Point the delegate to the GetInfoForm function in my
'MDI form object instance
getInfoDelegate = New GetInfoForm_Del egate(AddressOf
AppMDI.GetInfoF orm)
'*** Problem occurs on the next line ***
inf = DirectCast(AppM DI.Invoke(getIn foDelegate), InfoForm)
End Function
///
When the code gets to the point of executing the AppMDI.Invoke method
(indicated above), this call never returns. My application sits there
completely locked until I eventually click the Stop button in the IDE. If I
put a breakpoint in the MDI.GetInfoForm function, the breakpoint does not
get hit.
Does anyone have any suggestions or clues as to how I can get this to work?
I just cannot see what I'm doing wrong here.
My thanks in advance,
--
(O)enone
this...
I have an application which uses an MDI window. When it is running, the
application creates an instance of a COM object, passes into it an instance
of a local .NET class from my application, and then calls a method of the
COM object.
The COM object uses a method (ShowInfoForm) in the provided .NET object to
display an information form within the MDI container. The ShowInfoForm
function itself calls a method on my MDI form (GetInfoForm) which actually
creates and displays the information form.
\\\ In my MDI form
'The GetInfoForm function opens and returns a new
'instance of the InfoForm
Public Function GetInfoForm() As InfoForm
Dim f As New InfoForm
f.MdiParent = Me
f.Show()
Return f
End Function
///
However, when the .NET class method is called from within the COM object, it
is running in a different thread to that of my main application (for reasons
I don't understand). This therefore leads to an error when my
MDI.GetInfoForm method tries to set the .MdiParent property of the
information form:
A first chance exception of type 'System.Argumen tException' occurred in
system.windows. forms.dll
Additional information: Controls created on one thread cannot be
parented
to a control on a different thread.
When I've had threading issues with forms before, I've always used the
Invoke method on the form to execute the code in the form's own thread. I
tried to do that here by using the following code:
\\\ In my .NET class:
'Create a delegate for the InfoForm function.
Public Delegate Function GetInfoForm_Del egate() As InfoForm
Public Function ShowInfoForm
Dim inf As InfoForm
Dim getInfoDelegate As GetInfoForm_Del egate
'Point the delegate to the GetInfoForm function in my
'MDI form object instance
getInfoDelegate = New GetInfoForm_Del egate(AddressOf
AppMDI.GetInfoF orm)
'*** Problem occurs on the next line ***
inf = DirectCast(AppM DI.Invoke(getIn foDelegate), InfoForm)
End Function
///
When the code gets to the point of executing the AppMDI.Invoke method
(indicated above), this call never returns. My application sits there
completely locked until I eventually click the Stop button in the IDE. If I
put a breakpoint in the MDI.GetInfoForm function, the breakpoint does not
get hit.
Does anyone have any suggestions or clues as to how I can get this to work?
I just cannot see what I'm doing wrong here.
My thanks in advance,
--
(O)enone
Comment