How can I get the line number which threw exception?

In a catch block, how can I get the line number which threw an exception?

If you need the line number for more than just the formatted stack trace you get from Exception.StackTrace, you can use the StackTrace class:

try
{
    throw new Exception();
}
catch (Exception ex)
{
    // Get stack trace for the exception with source file information
    var st = new StackTrace(ex, true);
    // Get the top stack frame
    var frame = st.GetFrame(0);
    // Get the line number from the stack frame
    var line = frame.GetFileLineNumber();
}

Note that this will only work if there is a pdb file available for the assembly.

Simple way, use the Exception.ToString() function, it will return the line after the exception description.

You can also check the program debug database as it contains debug info/logs about the whole application.

If you don't have the .PBO file:

C#

public int GetLineNumber(Exception ex)
{
    var lineNumber = 0;
    const string lineSearch = ":line ";
    var index = ex.StackTrace.LastIndexOf(lineSearch);
    if (index != -1)
    {
        var lineNumberText = ex.StackTrace.Substring(index + lineSearch.Length);
        if (int.TryParse(lineNumberText, out lineNumber))
        {
        }
    }
    return lineNumber;
}

Vb.net

Public Function GetLineNumber(ByVal ex As Exception)
    Dim lineNumber As Int32 = 0
    Const lineSearch As String = ":line "
    Dim index = ex.StackTrace.LastIndexOf(lineSearch)
    If index <> -1 Then
        Dim lineNumberText = ex.StackTrace.Substring(index + lineSearch.Length)
        If Int32.TryParse(lineNumberText, lineNumber) Then
        End If
    End If
    Return lineNumber
End Function

Or as an extentions on the Exception class

public static class MyExtensions
{
    public static int LineNumber(this Exception ex)
    {
        var lineNumber = 0;
        const string lineSearch = ":line ";
        var index = ex.StackTrace.LastIndexOf(lineSearch);
        if (index != -1)
        {
            var lineNumberText = ex.StackTrace.Substring(index + lineSearch.Length);
            if (int.TryParse(lineNumberText, out lineNumber))
            {
            }
        }
        return lineNumber;
    }
}   

You could include .PDB symbol files associated to the assembly which contain metadata information and when an exception is thrown it will contain full information in the stacktrace of where this exception originated. It will contain line numbers of each method in the stack.

Check this one

StackTrace st = new StackTrace(ex, true);
//Get the first stack frame
StackFrame frame = st.GetFrame(0);

//Get the file name
string fileName = frame.GetFileName();

//Get the method name
string methodName = frame.GetMethod().Name;

//Get the line number from the stack frame
int line = frame.GetFileLineNumber();

//Get the column number
int col = frame.GetFileColumnNumber();

I added an extension to Exception which returns the line, column, method, filename and message:

public static class Extensions
{
    public static string ExceptionInfo(this Exception exception)
    {

        StackFrame stackFrame = (new StackTrace(exception, true)).GetFrame(0);
        return string.Format("At line {0} column {1} in {2}: {3} {4}{3}{5}  ",
           stackFrame.GetFileLineNumber(), stackFrame.GetFileColumnNumber(),
           stackFrame.GetMethod(), Environment.NewLine, stackFrame.GetFileName(),
           exception.Message);

    }
}

I tried using the solution By @davy-c but had an Exception "System.FormatException: 'Input string was not in a correct format.'", this was due to there still being text past the line number, I modified the code he posted and came up with:

int line = Convert.ToInt32(objErr.ToString().Substring(objErr.ToString().IndexOf("line")).Substring(0, objErr.ToString().Substring(objErr.ToString().IndexOf("line")).ToString().IndexOf("\r\n")).Replace("line ", ""));

This works for me in VS2017 C#.

Update to the answer

    // Get stack trace for the exception with source file information
    var st = new StackTrace(ex, true);
    // Get the top stack frame
    var frame = st.GetFrame(st.FrameCount-1);
    // Get the line number from the stack frame
    var line = frame.GetFileLineNumber();

Extension Method

static class ExceptionHelpers
{
	public static int LineNumber(this Exception ex)
	{
		int n;
		int i = ex.StackTrace.LastIndexOf(" ");
		if (i > -1)
		{
			string s = ex.StackTrace.Substring(i + 1);
			if (int.TryParse(s, out n))
				return n;
		}
		return -1;
	}
}

Usage

try
{
    throw new Exception("A new error happened");
}
catch (Exception ex)
{
    //If error in exception LineNumber() will be -1
    System.Diagnostics.Debug.WriteLine("[" + ex.LineNumber() + "] " + ex.Message);
}

Line numbers will be included in the stack trace if the library which generated the exception is compiled with debug symbols. This can be a separate file (*.pdb) or embedded in the library.

For .NET Core, .NET 5 and later, to have full exception line numbers in release builds, configure the project as follows:

<PropertyGroup>    
  <DebugSymbols>true</DebugSymbols>
  <DebugType>embedded</DebugType>

    <!-- Only enable the following if the line numbers mismatch -->
    <!--<Optimize>false</Optimize>-->
    
    <!--
      Additional properties which may impact how printed line numbers match the source code line numbers are listed here:
      https://docs.microsoft.com/en-us/dotnet/core/run-time-config/compilation
    -->
</PropertyGroup>

The above configuration will include debug symbols directly with the built files, which can be published as nugets.

An alternative to the above is to restore debug packages together with the main nuget packages, which is currently not yet supported: https://github.com/NuGet/Home/issues/9667

Now get the exception line numbers:

try
{
    throw new Exception();
}
catch (Exception ex)
{
    // Get stack trace for the exception with source file information
    var st = new StackTrace(ex, true);
    // Get the top stack frame
    var frame = st.GetFrame(0);
    // Get the line number from the stack frame
    var line = frame.GetFileLineNumber();
}

If your stack trace is bigger than one it should be:

var st = new StackTrace(es, true);
// Get the top stack frame
var frame = st.GetFrame(st.FrameCount - 1);

// Get the line number from the stack frame var line = frame.GetFileLineNumber();

Working for me:

var st = new StackTrace(e, true);

// Get the bottom stack frame
var frame = st.GetFrame(st.FrameCount - 1);
// Get the line number from the stack frame
var line = frame.GetFileLineNumber();
var method = frame.GetMethod().ReflectedType.FullName;
var path = frame.GetFileName();

In Global.resx file there is an event called Application_Error

it fires whenever an error occurs,,you can easily get any information about the error,and send it to a bug tracking e-mail.

Also i think all u need to do is to compile the global.resx and add its dll's (2 dlls) to your bin folder and it will work!