C# Interop with dll
- by Jim Jones
Using VS2008 C#
am attempting to interop a C++ dll.
Have a C++ class constructor:
make_summarizer(const char* rdir, const char* lic, const char* key);
Need to retain a reference to the object that is created so I can use it in a follow-on function.
When I did this in JNI the c code was:
declare a static pointer to the object:
static summarizer* summrzr;
Then in one of the functions I called this constructor as follows:
summrzr = make_summarizer(crdir, clic, ckey);
Where the parameters all where the requisite const char* type;
So in C#
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;
using System.Configuration;
namespace SummarizerApp
{
class SummApp
{
private IntPtr summarzr;
public SummApp()
{
string resource_dir = ConfigurationManager.AppSettings["resource_dir"];
string license = ConfigurationManager.AppSettings["license"];
string key = ConfigurationManager.AppSettings["key"];
createSummarizer(resource_dir, license, key);
}
[System.Runtime.InteropServices.DllImportAttribute("lib\\summarizer37.dll", EntryPoint = "#1")]
public static extern IntPtr make_summarizer(
[InAttribute()][MarshalAsAttribute(UnmanagedType.LPTStr)] string rdir,
[InAttribute()][MarshalAsAttribute(UnmanagedType.LPTStr)] string lic,
[InAttribute()][MarshalAsAttribute(UnmanagedType.LPTStr)] string key);
public void createSummarizer(string resource_dir, string license, string key)
{
try
{
this.summarzr = make_summarizer(resource_dir, license, key);
}
catch (AccessViolationException e)
{
Console.WriteLine(e.Message);
Console.WriteLine(e.StackTrace);
}
}
Have also tried using IntPtr created using Marshal.StringToHGlobalAnsi(string).
Regardless I get a AccessViolationException on the line where I call the native constructor;
So what am I doing wrong?
Jim
