TargetInvocationException

[tcomer]

Hello,

I'm receiving a "TargetInvocationException" on the follow line of
code:

datagridServers.Invoke(new
UpdateDisplayCallback(this.UpdateServerDisplay), new object[]
{ server });

The method:

private void AddServer(MyServerClass server){
if(server != null)
arraylistServers.Add(server);

if(datagridServers.InvokeRequired)
datagridServers.Invoke(new
UpdateDisplayCallback(this.UpdateServerDisplay), new object[]
{ server });
else
this.UpdateServerDisplay(server);
}

The signature for UpdateServerDisplay is "private void
UpdateServerDisplay(MyServerClass server)"
The signature for UpdateDisplayCallback is "private delegate void
UpdateDisplayCallback(MyServerClass server)"

In one of many attempts to solve the problem, I placed a breakpoint on
the line ("if(server != null)") and the 'server' instance contains
everything that it should contain, meaning that it is an instance of
MyServerClass. But when I compile and run the application, I get a
TargetInvocationException on the line I pointed out above, and the
InnerException says "Unable to cast object of type
'App.ServerInfoClass' to type 'App.MyServerClass'. It seems that it's
trying to cast a ServerInfoClass into a MyServerClass, for no reason?

I can't seem to find where I'm going wrong here. Stepping through the
program, I'm passing the correct type to the method, but it seems to
have a problem with the "datagridServers.Invoke...") line. I've been
trying to figure this out for a few days, at no avail ofcourse. Any
hints would be greatly appreciated. Thanks

[Peter Duniho]

On Wed, 12 Dec 2007 20:10:20 -0800, tcomer <tc****@gmail.comwrote:

[...]
In one of many attempts to solve the problem, I placed a breakpoint on
the line ("if(server != null)") and the 'server' instance contains
everything that it should contain, meaning that it is an instance of
MyServerClass.

The exception you describe (the inner one, that is) is specifically
telling you that it's _not_ an instance of MyServerClass, at least not of
the MyServerClass the method and delegate in question is expecting.

But when I compile and run the application, I get a
TargetInvocationException on the line I pointed out above, and the
InnerException says "Unable to cast object of type
'App.ServerInfoClass' to type 'App.MyServerClass'. It seems that it's
trying to cast a ServerInfoClass into a MyServerClass, for no reason?

My experience has been that the .NET runtime doesn't cast things "for no
reason".

In this particular case, _some_ cast has to occur, because the code
receiving the object only gets it as an instance of an "object". So
apparently, in spite of the instance looking a lot like what you know of
as a MyServerClass, it in fact is something else.

The cast doesn't happen "for no reason", and it fails because the object
isn't a type compatible with the desired type.

I can't seem to find where I'm going wrong here. Stepping through the
program, I'm passing the correct type to the method, but it seems to
have a problem with the "datagridServers.Invoke...") line. I've been
trying to figure this out for a few days, at no avail ofcourse. Any
hints would be greatly appreciated. Thanks

You'll probably need to post a concise-but-complete example of code that
reliably reproduces the problem.

The code you posted doesn't include any of the parts that would actually
be relevant. Looking at the line that generates the error is not enough
when the error is related to how the objects in question are created and
how their types are defined.

Obviously there's some sort of type incompatibility going on, and if I had
to guess I'd suspect types coming from two different assemblies. But
that's just a guess and there's no way to actually know what's going on
without more information.

Pete