How to get the exact location of an exception in C#, as can be done in VB.net?-CodePudding

First of all ...
I tried posting this question earlier, but didn't explain it properly, and it was just confusing people. So I deleted the old question and tried a complete re-write, with a completely different title.

And ... I've searched stack overflow, and there are related questions, but none of them answer this question. I would be very grateful for any help you could provide. The supplied answers on other stackoverflow questions don't solve the problem of compiler and dotfuscator changing the line numbers. I'm looking for a way to implement the VB solution below in a C# program

My test system:
-Windows 10
-VS2022
-C#
-.Net Framework 4.8
-WinForms

What I'm Trying to Accomplish:
We are trying to build an error reporting system in C# that will give the exact line number that throws an exception. It needs to work with the compiled release .exe file. It is easy to do this in VB.net, but I can't find a way to accomplish this in C#.

Here is how to get an exact location in VB.net:

    10:     On Error Resume Next
    20:     Err.Raise(60000)
    ' Returns 20.
    30:     MsgBox(Erl())

The above code is from the Microsoft documentation here, showing usage of the ErrObject.Erl property, which was carried over from VB6. I used that system to build an extensive error reporting capability back when I was a VB6 programmer. It was an extremely useful tool that allowed any end-user in the world to report detailed error information back to the Mother Ship (the developers). This allowed us to rapidly home in on the problem and do the necessary re-factoring.

Of course it is better to eliminate errors to begin with, but when shareware is being downloaded by a million users all over the world, on many different versions of Windows, with varying locality settings, there are going to be errors that don't pop up in beta testing.

Unfortunately, I'm not able to find any way in C# to add number tags at the beginning of code lines, like the 10:, 20:, 30: above. Those are not Visual Studio line numbers ... they are typed in by the programmer to label each line in the code as described in the Microsoft documentation here. I've also not found any way to get the Microsoft ErrObject working in C#, like it does in VB.net.

Here is what I've tried in C#:
Here is my test code:

    private void button2_Click(object sender, EventArgs e)
    {
        try
        {
            int x = 10;      // This is line 38 in the editor window
            int y = 0;
            int z = 0;
            z = x / y;       // This is line 41,throwing the exception (divide by zero)
        }
        catch (System.Exception ex)
        {
            MessageBox.Show(ex.ToString());
        }
    }

The Problem:
The ex.ToString() always returns the first line of the try block (in this example, line 38), instead of returning the actual line that triggered the error (line 41). This is ALSO TRUE OF the other answers on stack overflow, involving StackTrace, etc.

My Question:
Is there a way in C# to get the exact code line that throws the exception, like we can do in VB.net? If so, how?

One Possible Solution
One person suggested it might be possible to increment an integer variable on every other line of code, then report that integer value with the exception. I appreciate that kind of creative thinking, but I'm hoping there will be other ideas as well. Thanks!!

Thanks!!
Any help you could provide would be sincerely appreciated.

CodePudding user response：

Ok ... we have the solution. You can run the compiler optimized, then run the Dotfuscator, and still get the exact error line number reported by the System.Exception Class. And ... there are no PDB files to help hackers crack your software.

Just set Debugging information to "Embedded."

Instructions for .Net Framework 4.8 instructions (Current as of VS2022):
(Step-by-Step to help new people)

Right-Click on your project and select "Properties"
In the left panel of the Properties window, select "Build"
Make sure that "Optimize Code" is selected (or not ... it's your choice)
Click the "Advanced" button, at the bottom-right of the screen
In the Advanced window, about 2/3 down, you'll see "Debugging information:" with a drop-down box.
Select "Embedded" and click "OK". The Advanced window disappears.

Instructions for .Net 6.0 (Current as of VS2022):

Right-Click on your project and select "Properties"
In the left panel of the Properties window, select "Build > General"
Under "Optimize Code", select "Release" (or not ... it's your choice)
Directly under "Optimize Code, you'll see "Debug Symbols" with a drop-down box.
Select "Embedded in DLL/EXE".
Close the Project Properties window.

Now ... rebuild (REbuild!) the release version with compiler optimized and debug set to embedded. Then run the dotfuscator, and your dotfuscated Release .exe will still get the accurate line number from the following code:

    catch (System.Exception ex)
    {
        MessageBox.Show(ex.ToString());
    }

Obviously, this example is bare-bones, but you can build a robust error-reporting system that includes this and other features built into the System.Exception Class (Microsoft documentation here). We intend to build a website that will receive the information from the desktop app, and store it into a DB as part of a basic service ticket system.

Performance Tests:

I set up a small app that runs a loop of simple math operations 200,000,000 repetitions, timing the results (average of 3 runs). Here are the results:

Compiler Optimized - Debugging information set to "None" - Dotfuscated:
Time: 4116.3 ms (no line number reported)

Compiler Optimized - Debugging information set to "Embedded" - Dotfuscated
Time: 4115.9 ms (exact line number reported!)

Hope this helps anybody who is interested in creating an error-reporting system for their software.

Best of luck to all!!

CodePudding user response：

Try this:

try
{
    int x = 10;      // This is line 38 in the editor window
    int y = 0;
    int z = 0;
    z = x / y;       // This is line 41,throwing the exception (divide by zero)
}
catch (Exception ex)
{
   int CodeLine = new System.Diagnostics.StackTrace(ex, true).GetFrame(0).GetFileLineNumber();
   MessageBox.Show(CodeLine.ToString());
}

CodePudding user response：

Getting the original line number from obfuscated code seems like a product feature that should be handled by the obfuscator. Alternatively, you could pre-process your the original .cs files, and the pre-processed files get passed to the obfuscator. For example, your input code is:

34 private void button2_Click(object sender, EventArgs e)
35    {
36        try
37        {
38            int x = 10;      // This is line 38 in the editor window
39            int y = 0;
40            int z = 0;
41            z = x / y;       // This is line 41,throwing the exception (divide by zero)
42        }
43        catch (System.Exception ex)
44        {
45            MessageBox.Show(ex.ToString());
46        }
47    }

Your pre-process takes the above code and inserts line numbers. Then this generated code is passed to the obfuscator.

private void button2_Click(object sender, EventArgs e)
    {
        int lineNumber = 36;
        try
        {
            lineNumber = 38;
            int x = 10;      // This is line 38 in the editor window
            lineNumber = 39;
            int y = 0;
            lineNumber = 40;
            int z = 0;
            lineNumber = 41;
            z = x / y;       // This is line 41,throwing the exception (divide by zero)
            lineNumber = 42;
        }
        catch (System.Exception ex)
        {
            // decide how to handle Exceptions. Possibly wrap the exception in a new custom exception
            // or write the line number and file to a log file
            throw new LineNumberWrapperException(lineNumber, ex);
        }
    }