调用非托管函数返回的char *烧焦 [英] calling unmanaged function char returns char *

问题描述

我在非托管的C / C ++ code（DLL）中的函数，返回包含字符数组的结构。我创建了C＃结构来接收这个返回值uppon调用该函数。而uppon调用这个函数时得到System.Runtime.InteropServices.MarshalDirectiveException

这是C声明：

  typedef结构T_SAMPLE_STRUCT {
INT NUM;
字符文本[20];
} SAMPLE_STRUCT;SAMPLE_STRUCT sampleFunction（SAMPLE_STRUCT SS）;
 

这是C＃声明：

 结构SAMPLE_STRUCT
{
    公众诠释NUM;
    公共字符串文本;
}类Dllwrapper
{
    函数[DllImport（samplecdll.dll）]
    公共静态外部SAMPLE_STRUCT sampleFunction（SAMPLE_STRUCT SS）;}
 

我使用1个字节的ASCII码。

有没有人有一个提示或如何做到这一点的解决方案？

解决方案

诀窍转换C数组成员使用的MarshalAs（UnmanagedType.ByValTStr）。这可以用来告诉CLR到阵列编组作为一个内嵌部件相对于一个正常的非内嵌阵列。试试下面的签名。

<$p$p><$c$c>[System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential,字符集= System.Runtime.InteropServices.CharSet.Ansi）
公共结构T_SAMPLE_STRUCT {    /// INT
    公众诠释NUM;    ///的char [20]
    [System.Runtime.InteropServices.MarshalAsAttribute(System.Runtime.InteropServices.UnmanagedType.ByValTStr, SizeConst = 20）]
    公共字符串文本;
}公共部分类NativeMethods {    ///返回类型：SAMPLE_STRUCT-＆GT; T_SAMPLE_STRUCT
    /// SS：SAMPLE_STRUCT-＆GT; T_SAMPLE_STRUCT
    [System.Runtime.InteropServices.DllImportAttribute（＆所述;未知＆gt;中，入口点=sampleFunction）]
公共静态外部T_SAMPLE_STRUCT sampleFunction（T_SAMPLE_STRUCT SS）;}

这签名是由PInovke互操作助理（链接）在$ C $提供赞助商CPLEX。它可以从本地code最PInvoke的签名会自动转换成C＃或VB.Net。

I have a function in unmanaged C/C++ code (dll) that returns a structure containing a char array. I created C# struct to receive this return value uppon calling the function. And uppon calling this function i get 'System.Runtime.InteropServices.MarshalDirectiveException'

This is C declaration:

typedef struct T_SAMPLE_STRUCT {
int num;
char text[20];
} SAMPLE_STRUCT;

SAMPLE_STRUCT sampleFunction( SAMPLE_STRUCT ss );

This is C# declaration:

struct SAMPLE_STRUCT
{
    public int num;
    public string text;
}

class Dllwrapper
{
    [DllImport("samplecdll.dll")]
    public static extern SAMPLE_STRUCT sampleFunction(SAMPLE_STRUCT ss);

}

I am using 1-byte ASCII.

Does anyone has a hint or a solution on how to do this?

解决方案

The trick to converting a C array member is to use the MarshalAs(UnmanagedType.ByValTStr). This can be used to tell the CLR to marshal the array as an inlined member vs. a normal non-inlined array. Try the following signature.

[System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential, CharSet=System.Runtime.InteropServices.CharSet.Ansi)]
public struct T_SAMPLE_STRUCT {

    /// int
    public int num;

    /// char[20]
    [System.Runtime.InteropServices.MarshalAsAttribute(System.Runtime.InteropServices.UnmanagedType.ByValTStr, SizeConst=20)]
    public string text;
}

public partial class NativeMethods {

    /// Return Type: SAMPLE_STRUCT->T_SAMPLE_STRUCT
    ///ss: SAMPLE_STRUCT->T_SAMPLE_STRUCT
    [System.Runtime.InteropServices.DllImportAttribute("<Unknown>", EntryPoint="sampleFunction")]
public static extern  T_SAMPLE_STRUCT sampleFunction(T_SAMPLE_STRUCT ss) ;

}

This signature is brought to you by the PInovke Interop Assistant (link) available on CodePlex. It can automatically translate most PInvoke signatures from native code to C# or VB.Net.

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