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.NET Forum / .NET Framework / Interop / April 2007

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const void*

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Sajan@community.nospam - 18 Apr 2007 23:41 GMT
From C# I am trying to call the following API
(http://msdn2.microsoft.com/en-us/library/ms684063.aspx)

JET_ERR JET_API JetSetColumn(
 JET_SESID sesid,
 JET_TABLEID tableid,
 JET_COLUMNID columnid,
 const void* pvData,
 unsigned long cbData,
 JET_GRBIT grbit,
 JET_SETINFO* psetinfo
);

To make the long story short, I need help with passing in the value for
"const void* pvData". Following is my function prototype

Thanks for your help
Sajan
Mattias Sjögren - 19 Apr 2007 05:45 GMT
>To make the long story short, I need help with passing in the value for
>"const void* pvData". Following is my function prototype

Looks like you forgot to include it.

Generally you can use whatever type is appropriate for pvData.

Mattias

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Mattias Sjögren [C# MVP]  mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.

Sajan@community.nospam - 19 Apr 2007 06:38 GMT
Oh sorry, here it is

public static extern int JetSetColumn(
         int sesid,
         int tableid,
         int columnid,
         IntPtr pvData,
         int cbData,
         int grbit,
         ref JET_SETINFO psetinfo);

> >To make the long story short, I need help with passing in the value for
>>"const void* pvData". Following is my function prototype
[quoted text clipped - 4 lines]
>
> Mattias
Walter Wang [MSFT] - 19 Apr 2007 08:51 GMT
Hi Sajan,

According to the documentation of the API JetSetColumn, pvData is an input
pointer to an allocated memory.

You could use Marshal.AllocHGlobal to allocate a block of memory and use
Marshal.Write* members to write data into the memory block.

After calling the API, don't forget to use Marshal.FreeHGlobal to free the
memory.

#Marshal Members (System.Runtime.InteropServices)
http://msdn2.microsoft.com/en-us/library/system.runtime.interopservices.mars
hal_members.aspx

Please feel free to reply here is there's anything unclear.

Sincerely,
Walter Wang (wawang@online.microsoft.com, remove 'online.')
Microsoft Online Community Support

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Sajan@community.nospam - 22 Apr 2007 06:57 GMT
Thanks Walter.

Sajan

> Hi Sajan,
>
[quoted text clipped - 40 lines]
> This posting is provided "AS IS" with no warranties, and confers no
> rights.

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