activeX array transfer

[Owen Woo]

My activeX control developped in VC++ has following method:
void AppendData(double* databuf)
How can I call this method in C# and transfer the databuf parameter to it?

[Nicholas Paldino [.NET/C# MVP]]

This should be declared as:

void AppendData(double[] databuf);

The reason it should be declared like this is because if you declare it
as "ref double" then it will pass only the first item of the array.

If the method modifies the array in any way, then this won't work
either. Because this is a C-style array, it doesn't know what was modified
in the unmanaged realm (SAFEARRAYs don't have this problem) and can't just
marshal all of the memory in the array back.

If the contents are modified, then you will have to declare databuf as
an IntPtr and then allocate the memory yourself (using the static Alloc*
methods on the Marshal class). Then you write to the unmanaged memory block
and pass it to the method. On return from the method, you have to read the
unmanaged memory back from the unmanaged memory block (and free the memory
block as well).

Hope this helps.
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard.caspershouse.com

"Owen Woo" <wo*****@163.net> wrote in message
news:uQ**************@TK2MSFTNGP12.phx.gbl...

My activeX control developped in VC++ has following method:
void AppendData(double* databuf)
How can I call this method in C# and transfer the databuf parameter to it?

[Owen Woo]

I compiled the control in VC++ and import the OCX into C#, the method was
defined by the system as following:
void AppendData(ref double databuf)
How can I declare the method by myself in C#?

"Nicholas Paldino [.NET/C# MVP]" <mv*@spam.guard.caspershouse.com> дÈëÏûÏ¢
ÐÂÎÅ:eK**************@tk2msftngp13.phx.gbl...

This should be declared as:

void AppendData(double[] databuf);

The reason it should be declared like this is because if you declare it as "ref double" then it will pass only the first item of the array.

If the method modifies the array in any way, then this won't work
either. Because this is a C-style array, it doesn't know what was modified in the unmanaged realm (SAFEARRAYs don't have this problem) and can't just
marshal all of the memory in the array back.

If the contents are modified, then you will have to declare databuf as
an IntPtr and then allocate the memory yourself (using the static Alloc*
methods on the Marshal class). Then you write to the unmanaged memory block and pass it to the method. On return from the method, you have to read the unmanaged memory back from the unmanaged memory block (and free the memory
block as well).

Hope this helps.
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard.caspershouse.com

"Owen Woo" <wo*****@163.net> wrote in message
news:uQ**************@TK2MSFTNGP12.phx.gbl...

My activeX control developped in VC++ has following method:
void AppendData(double* databuf)
How can I call this method in C# and transfer the databuf parameter to it?