Cannot pass %s as ref or out, because %s is a marshal-by-reference class

[Max]

public class Entity : System.Windows.Forms.Label
{
....
protected System.Drawing.Point lastMousePosition;
....
}

public class Flow : Entity
{
....
protected override void OnMouseMove( System.Windows.Forms.MouseEventArgs
e )
{
int deltaX = MousePosition.X - lastMousePosition.X;
int deltaY = MousePosition.Y - lastMousePosition.Y;
...
}
....
}

This code causes an error:

Cannot pass ...lastMousePosition as ref or out, because ...lastMousePosition
is a marshal-by-reference class

What does it mean? What is wrong with the code?

[Max]

The problem is solved by adding

protected System.Drawing.Size Delta
{
get
{
return new
System.Drawing.Size(MousePosition.X-lastMousePosition.X,MousePosition.Y-last
MousePosition.Y);
}
}

to Entity class and using this property in Flow.OnMouseMove.

But I still do not understanf what was wrong with the code as it was?
"Max" <Pl****@reply.to.news.group> wrote in message
news:uH****************@tk2msftngp13.phx.gbl...

public class Entity : System.Windows.Forms.Label
{
...
protected System.Drawing.Point lastMousePosition;
...
}

public class Flow : Entity
{
...
protected override void OnMouseMove( System.Windows.Forms.MouseEventArgs e )
{
int deltaX = MousePosition.X - lastMousePosition.X;
int deltaY = MousePosition.Y - lastMousePosition.Y;
...
}
...
}

This code causes an error:

Cannot pass ...lastMousePosition as ref or out, because ....lastMousePosition is a marshal-by-reference class

What does it mean? What is wrong with the code?

[Aravind C]

Hi Max,

I am not if I am missing something from your code snippet that could cause
the error, but I seem to be able to compile the same code correctly - The
compiler does not seem to complain if I use the below code snippets that you
posted.

public class Entity : System.Windows.Forms.Label
{
protected System.Drawing.Point lastMousePosition;
}

public class Flow : Entity
{
protected override void OnMouseMove(System.Windows.Forms.MouseEventArgs e)
{
int deltaX = MousePosition.X - lastMousePosition.X;
int deltaY = MousePosition.Y - lastMousePosition.Y;
}
}

Let me know and we can look into the issue a little more.

Regards,
Aravind C
"Max" <Pl****@reply.to.news.group> wrote in message
news:uH**************@tk2msftngp13.phx.gbl...

public class Entity : System.Windows.Forms.Label
{
...
protected System.Drawing.Point lastMousePosition;
...
}

public class Flow : Entity
{
...
protected override void OnMouseMove( System.Windows.Forms.MouseEventArgs e )
{
int deltaX = MousePosition.X - lastMousePosition.X;
int deltaY = MousePosition.Y - lastMousePosition.Y;
...
}
...
}

This code causes an error:

Cannot pass ...lastMousePosition as ref or out, because ....lastMousePosition is a marshal-by-reference class

What does it mean? What is wrong with the code?

[Max]

Thank you for trying.

Probably it depends on the version of Visual Studio or .NET framework.
I am using Visual Studio 2002 (and framework 1.0) and you?
I did not check it in framework 1.1.

Anyway, by now the problem is "academic" only. I've just rewritten the code
in another way and got rid of the error.
"Aravind C" <ar***********@nospam.hotmail.com> wrote in message
news:eo**************@TK2MSFTNGP12.phx.gbl...

Hi Max,

I am not if I am missing something from your code snippet that could cause
the error, but I seem to be able to compile the same code correctly - The
compiler does not seem to complain if I use the below code snippets that you posted.

public class Entity : System.Windows.Forms.Label
{
protected System.Drawing.Point lastMousePosition;
}

public class Flow : Entity
{
protected override void OnMouseMove(System.Windows.Forms.MouseEventArgs e) {
int deltaX = MousePosition.X - lastMousePosition.X;
int deltaY = MousePosition.Y - lastMousePosition.Y;
}
}

Let me know and we can look into the issue a little more.

Regards,
Aravind C
"Max" <Pl****@reply.to.news.group> wrote in message
news:uH**************@tk2msftngp13.phx.gbl...

public class Entity : System.Windows.Forms.Label
{
...
protected System.Drawing.Point lastMousePosition;
...
}

public class Flow : Entity
{
...
protected override void OnMouseMove(

System.Windows.Forms.MouseEventArgs

e )
{
int deltaX = MousePosition.X - lastMousePosition.X;
int deltaY = MousePosition.Y - lastMousePosition.Y;
...
}
...
}

This code causes an error:

Cannot pass ...lastMousePosition as ref or out, because

...lastMousePosition

is a marshal-by-reference class

What does it mean? What is wrong with the code?

[Aravind C]

Hi Max,

Yes, that could possibly be a reason.
I am on .NET 1.1.

Regards,
Aravind C
"Max" <Pl****@reply.to.news.group> wrote in message
news:eM**************@TK2MSFTNGP12.phx.gbl...

Thank you for trying.

Probably it depends on the version of Visual Studio or .NET framework.
I am using Visual Studio 2002 (and framework 1.0) and you?
I did not check it in framework 1.1.

Anyway, by now the problem is "academic" only. I've just rewritten the code in another way and got rid of the error.
"Aravind C" <ar***********@nospam.hotmail.com> wrote in message
news:eo**************@TK2MSFTNGP12.phx.gbl...

Hi Max,

I am not if I am missing something from your code snippet that could cause the error, but I seem to be able to compile the same code correctly - The compiler does not seem to complain if I use the below code snippets that you

posted.

public class Entity : System.Windows.Forms.Label
{
protected System.Drawing.Point lastMousePosition;
}

public class Flow : Entity
{
protected override void

OnMouseMove(System.Windows.Forms.MouseEventArgs e)

{
int deltaX = MousePosition.X - lastMousePosition.X;
int deltaY = MousePosition.Y - lastMousePosition.Y;
}
}

Let me know and we can look into the issue a little more.

Regards,
Aravind C
"Max" <Pl****@reply.to.news.group> wrote in message
news:uH**************@tk2msftngp13.phx.gbl...

public class Entity : System.Windows.Forms.Label
{
...
protected System.Drawing.Point lastMousePosition;
...
}

public class Flow : Entity
{
...
protected override void OnMouseMove(

System.Windows.Forms.MouseEventArgs

e )
{
int deltaX = MousePosition.X - lastMousePosition.X;
int deltaY = MousePosition.Y - lastMousePosition.Y;
...
}
...
}

This code causes an error:

Cannot pass ...lastMousePosition as ref or out, because

...lastMousePosition

is a marshal-by-reference class

What does it mean? What is wrong with the code?