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How to copy a String into a struct using C#

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10 Jun 2004 108.1K   17   17
How to copy a String into a struct using C#

Introduction

This article show a simple code snippet using which you can copy a string into a struct.

Using the code

C#
using System;
using System.Runtime.InteropServices;
using System.Text;

class Class1
{

    [StructLayout(LayoutKind.Sequential, CharSet=CharSet.Unicode)]
    public struct MyStruct
    {
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst=4)] public string fname;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst=4)] public string lname;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst=7)] public string phone;
    }
    
    public static void Main()
    {
        string buffer = "abcdefgh2223333";
        IntPtr pBuf = Marshal.StringToBSTR(buffer);
        MyStruct ms = (MyStruct)Marshal.PtrToStructure(pBuf,typeof(MyStruct));
        Console.WriteLine("fname is: {0}",ms.fname);
        Console.WriteLine("lname is: {0}",ms.lname);
        Console.WriteLine("phone is: {0}",ms.phone);
        Marshal.FreeBSTR(pBuf);
    }
}

License

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Comments and Discussions

 
GeneralMarshalling BSTR * Pin
buratino224-Jun-07 21:48
buratino224-Jun-07 21:48 
GeneralMixed structures Pin
Mancunian21-Apr-06 3:00
Mancunian21-Apr-06 3:00 
QuestionIs it possible to create a function of this? Pin
Anonymous7-Apr-05 17:37
Anonymous7-Apr-05 17:37 
AnswerRe: Is it possible to create a function of this? Pin
dgiljr8-Apr-05 4:16
dgiljr8-Apr-05 4:16 
GeneralRe: Is it possible to create a function of this? Pin
Anonymous26-Apr-05 15:08
Anonymous26-Apr-05 15:08 
Generalpointless Pin
leppie10-Jun-04 7:12
leppie10-Jun-04 7:12 
GeneralRe: pointless Pin
dgiljr10-Jun-04 8:35
dgiljr10-Jun-04 8:35 
GeneralRe: pointless Pin
soumyasg28-Oct-06 18:12
soumyasg28-Oct-06 18:12 
GeneralGood, but... Pin
casperOne10-Jun-04 2:15
casperOne10-Jun-04 2:15 
GeneralRe: Good, but... Pin
dgiljr10-Jun-04 4:32
dgiljr10-Jun-04 4:32 
GeneralRe: Good, but... Pin
casperOne10-Jun-04 6:21
casperOne10-Jun-04 6:21 
GeneralRe: Good, but... Pin
dgiljr10-Jun-04 8:32
dgiljr10-Jun-04 8:32 
GeneralRe: Good, but... Pin
casperOne10-Jun-04 8:52
casperOne10-Jun-04 8:52 
GeneralRe: Good, but... Pin
Mark Abela10-Jun-04 12:21
Mark Abela10-Jun-04 12:21 
Diego,

I think you should be congratulated for, as we say in the land of OZ, "having a go". This topic is of interest to me and is far from "pointless" when you have to interact with existing systems.

I took a different approach to resolve the moving field issue, using individual Marshal calls and an enum to define the field positions.

public class SomePacket<br />
{<br />
enum Fields {<br />
	PktLength,<br />
	PktLenghByte2,		// Pad out the length with additional fields<br />
	Command,<br />
	CommandByte2,<br />
	CommandByte3,<br />
	CommandByte4,<br />
	SmallIntData,<br />
	SmallIntDataByte2,<br />
	Last<br />
}<br />
<br />
private Int16 m_smallData;<br />
<br />
public int ToBuffer(Byte [] buf, int offset /* offset to start writing buffer*/)<br />
{<br />
	Marshal.WriteInt16(buf, offset + (int)Fields.PktLength], (int_Fields.Last);<br />
	Marshal.WriteInt32(buf, offset + (int)Fields.Command], 1234);<br />
	Marshal.WriteInt16(buf, offset + (int)Fields. SmallIntData], m_smallData);<br />
}<br />
} 

Another issue with you approach is the extra marshal into a string, what happens is the data contains a null, not to mention the overhead of an extra copy.

Cheers,
Mark Abela



Mark Abela
Software Engineer
Inner Range
GeneralRe: Good, but... Pin
dgiljr11-Jun-04 3:57
dgiljr11-Jun-04 3:57 
GeneralRe: Good, but... Pin
Mark Abela14-Jun-04 11:42
Mark Abela14-Jun-04 11:42 
GeneralRe: Good, but... Pin
dgiljr15-Jun-04 3:46
dgiljr15-Jun-04 3:46 

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