“无法在dll中找到名为[function]的入口点” （c ++到c＃类型的转换） [英] "Unable to find an entry point named [function] in dll" (c++ to c# type conversion)

问题描述

我有一个来自第三方的dll，它是用C ++编写的。
这里有一些来自dll文档的信息：

  //启动文档
 
 RECO_DATA {
 wchar_t姓[200]; 
 wchar_t名字[200]; 
} 
  

说明：
接收函数结果的数据结构。所有函数结果将以$ Unicode（UTF-8）的形式存储
。

方法：

  bool recoCHN_P_Name（char * imgPath，RECO_DATA * o_data）; 
  

输入：

 code> char * imgPath 
  

此
的图像位置的完整路径功能识别

  RECO_DATA * o_data 
  

数据对象，用于接收函数
结果。
函数return：
如果Success，否则为false，则返回true。

  // end documentation 
  

我正在尝试从C＃应用程序调用recoCHN_P_Name。为此，我想出了这个代码：

导入dll的代码：

  public class cnOCRsdk 
 {
 [StructLayout（LayoutKind.Sequential，CharSet = CharSet.Unicode）] 
 public struct RECO_DATA {
 [MarshalAs（UnmanagedType。 ByValTStr，SizeConst = 200）] 
 public string FirstName; 
 [MarshalAs（UnmanagedType.ByValTStr，SizeConst = 200）] 
 public string Surname; 
} 
 
 [DllImport（@cnOCRsdk.dll，EntryPoint =recoCHN_P_Name）] 
 public static extern bool recoCHN_P_Name（byte [] imgPath，RECO_DATA o_data）; 
} 
  

调用函数的代码：

  cnOCRsdk.RECO_DATA recoData = new cnOCRsdk.RECO_DATA（）; 
 
 string path = @C：\WINDOWS\twain_32\twainrgb.bmp; 
 
 System.Text.ASCIIEncoding encoding = new System.Text.ASCIIEncoding（）; 
 byte [] bytes = encoding.GetBytes（path）; 
 
 bool res = cnOCRsdk.recoCHN_P_Name（bytes，recoData）; 
  

我得到的错误是
无法找到一个名为cnOCRsdk.dll中的recoCHN_P_Name。
我怀疑我将一个类型从C ++转换为C＃时出错，但是在哪里？$ / $ b

解决方案

首先确保该函数实际导出：

在Visual Studio命令提示符下，使用 dumpbin / exports whatever.dll

I have a dll which comes from a third party, which was written in C++. Here is some information that comes from the dll documentation:

//start documentation

RECO_DATA{
wchar_t Surname[200];
wchar_t Firstname[200];
}

Description: Data structure for receiving the function result. All function result will be stored as Unicode (UTF-8).

Method:

bool recoCHN_P_Name(char *imgPath,RECO_DATA *o_data);

Input:

char * imgPath

the full path of the image location for this function to recognize

RECO_DATA * o_data

data object for receiving the function result. Function return: True if Success, otherwise false will return.

//end documentation

I am trying to call the recoCHN_P_Name from my C# application. To this end, I came up with this code:

The code to import the dll:

    public class cnOCRsdk
{
    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
    public struct RECO_DATA{
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst=200)]
        public string FirstName;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 200)]
        public string Surname;
        }

    [DllImport(@"cnOCRsdk.dll", EntryPoint="recoCHN_P_Name")]
    public static extern bool recoCHN_P_Name(byte[] imgPath, RECO_DATA o_data);
}

The code to call the function:

            cnOCRsdk.RECO_DATA recoData = new cnOCRsdk.RECO_DATA();

        string path = @"C:\WINDOWS\twain_32\twainrgb.bmp";

        System.Text.ASCIIEncoding encoding = new System.Text.ASCIIEncoding();
        byte[] bytes = encoding.GetBytes(path);

        bool res = cnOCRsdk.recoCHN_P_Name(bytes, recoData);

And the error I'm getting is ""Unable to find an entry point named 'recoCHN_P_Name' in DLL 'cnOCRsdk.dll'." I'm suspecting that I'm having an error in converting a type from C++ to C#. But where exactly ... ?

解决方案

First make sure the function is actually exported:

In the Visual Studio Command Prompt, use dumpbin /exports whatever.dll

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