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Jun 26th, 2009

Fixed size structure in C#

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

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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niketan

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Jun 26th, 2009

Re: Fixed size structure in C#

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

VIeditorlover

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Jun 26th, 2009

Re: Fixed size structure in C#

Import - using System.Runtime.InteropServices;

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.

adatapost

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Posting Genius

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Jun 26th, 2009

Re: Fixed size structure in C#

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

sknake

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Jun 27th, 2009

Re: Fixed size structure in C#

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

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);
..

So the size of struct is 14 bytes.

adatapost

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