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Fixed size structure in C#

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Join Date: Jul 2008

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niketan

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Fixed size structure in C#

Jun 26th, 2009

Hello,
How can I define fixed size of structure in c#..
e.g.

 Help with Code Tags 
 C# Syntax (Toggle Plain Text) 
struct xyz{
char localc[12];
short localshort;
};
 
I had made a c# structure like this 
[StructLayout(LayoutKind.Sequential,  Pack = 2,CharSet=CharSet.Ansi, Size = 14)]
struct xyz{
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 12)]
public char[] localc;
short localshort;
}
 
xyz abc = new xyz();
struct xyz{
char localc[12];
short localshort;
};

I had made a c# structure like this 
[StructLayout(LayoutKind.Sequential,  Pack = 2,CharSet=CharSet.Ansi, Size = 14)]
struct xyz{
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 12)]
public char[] localc;
short localshort;
}

xyz abc = new xyz();

Here i am not able to get the sizeof abc as 14 ..and got error while mashal.sizeof(abc);
How should i preallocate memory of size of structure ?
I can easily does that in c/c++ by just declaring it .. how to make this possible in c#?
and i can initialise the structure using memset in c .. whats its alternative in c#?

It will be helpful to get the solution

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Join Date: Dec 2007

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VIeditorlover VIeditorlover is offline

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Re: Fixed size structure in C#

Jun 26th, 2009

I am not sure about that, but unsafe could do the trick...

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Join Date: Oct 2008

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adatapost

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Posting Maven

Re: Fixed size structure in C#

Jun 26th, 2009

Import - using System.Runtime.InteropServices;

 Help with Code Tags 
 C# Syntax (Toggle Plain Text) 
 xyz p = new xyz();
 MessageBox.Show(Marshal.SizeOf(p).ToString());
 xyz p = new xyz();
 MessageBox.Show(Marshal.SizeOf(p).ToString());

Read this http://msdn.microsoft.com/en-us/libr...ya(VS.80).aspx

Last edited by adatapost; Jun 26th, 2009 at 9:08 am.

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sknake

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.NET Enthusiast

Re: Fixed size structure in C#

Jun 26th, 2009

In .NET the char data type is is 16bit, most other languages it is 8bit. You will also need to watch out for that.

Scott Knake
Custom Software Development
Apex Software, Inc.

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Join Date: Oct 2008

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adatapost

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Posting Maven

Re: Fixed size structure in C#

Jun 27th, 2009

Because of this unmanaged attribute a size of char is 8 bits.

 Help with Code Tags 
 C# Syntax (Toggle Plain Text) 
 [StructLayout(LayoutKind.Sequential, Pack = 2, CharSet = CharSet.Ansi, Size = 14)]
        struct xyz
        {
            [MarshalAs(UnmanagedType.ByValArray, SizeConst = 12)]
            public char[] localc;
            short localshort;
        }
  ...
  ...
xyz p = new xyz();
int size=Marshal.SizeOf(p);
..
 [StructLayout(LayoutKind.Sequential, Pack = 2, CharSet = CharSet.Ansi, Size = 14)]
        struct xyz
        {
            [MarshalAs(UnmanagedType.ByValArray, SizeConst = 12)]
            public char[] localc;
            short localshort;
        }
  ...
  ...
xyz p = new xyz();
int size=Marshal.SizeOf(p);
..