When you want to exclude a method from showing up in the stack trace, you can apply the StackTraceHidden attribute to the method:
[System.Diagnostics.StackTraceHidden]
public static void Throw()
{
//check conditions and throw
}
Code language: C# (cs)Note: This attribute was added in .NET 6.
You can apply StackTraceHidden to a class to hide all of its methods from the stack trace:
[System.Diagnostics.StackTraceHidden]
public static class Helpers
{
//lots of exception thrower helper methods
}
Code language: C# (cs)Use StackTraceHidden with throw helper methods
StackTraceHidden is very useful for hiding throw helper methods. Devs often use these methods to get rid of redundant if-then-throw statements. The problem is these methods pollute the stack trace. Hereโs an example of what the stack trace looks like when you call ArgumentNullException.ThrowIfNull():
System.ArgumentNullException: Value cannot be null. (Parameter 'employee.FirstName')
at System.ArgumentNullException.Throw(String paramName)
at System.ArgumentNullException.ThrowIfNull(Object argument, String paramName)
at Program.Process(Employee employee) in D:\Program.cs:line 19
Code language: plaintext (plaintext)You can use the StackTraceHidden attribute to eliminate the throw helper methods from the stack trace. Hereโs an example of writing a method thatโs equivalent to ArgumentNullException.ThrowIfNull() except itโs hidden from the stack trace:
using System.Runtime.CompilerServices;
using System.Diagnostics.CodeAnalysis;
[System.Diagnostics.StackTraceHidden]
public static class Helpers
{
public static void ThrowIfNull([NotNull] object? argument,
[CallerArgumentExpression("argument")] string paramName = null)
{
if (argument == null)
{
throw new ArgumentNullException(paramName);
}
}
}
Code language: C# (cs)Note: Itโs also using the CallerArgumentExpression attribute to automatically get the argument names.
Hereโs the stack trace now. Notice it doesnโt have the Helpers.ThrowIfNull() call in it:
System.ArgumentNullException: Value cannot be null. (Parameter 'employee.FirstName')
at Program.Process(Employee employee) in D:\Program.cs:line 19Code language: plaintext (plaintext)
For methods like ThrowIfNull(employee), is there a way to tell the static analyzers that in subsequent statements, employee will not be null?
Good question. So Iโm assuming youโre referring to the Nullable feature and specifically warning CS8604 (โx could be nullโ).
To get rid of that warning in the calling code, update the null-checking method to use [NotNull]object? argument (instead of the non-nullable โ object argument), like this:
public static void ThrowIfNull([NotNull]object? argument, โฆ.).
This makes it so the analyzer knows that the object was null-checked and therefore wonโt be null after this method is called.
This is actually what the built-in ArgumentNullException.ThrowIfNull() has, and I totally missed it because I didnโt have the Nullable feature turned on at the time. Iโll go ahead and update the code example in the article with this change too.
nm. I found the [System.Diagnostics.CodeAnalysis.NotNull] attribute
Oops. You beat me to it. Thank you!
(note from Mak โ combined these two comments)
๐ Youโre welcome!
Hey Mak, Is this available in .net framework?
I just add that attribute into my code(net472, VS2022), and it doesnโt work.
Hey Joe,
This attribute was added in .NET 6. So unfortunately, no, itโs not available in your .NET Framework version.
Trying to use this attribute in a project using c# 8. It is not part of System.Diagnostics and yields an error.
Please help.
Hi Chris,
Unfortunately this attribute was added in .NET 6, so itโs not available in older versions. You could try to implement this behavior yourself. Letโs say youโre logging exceptions in a centralized method (like Logger.Error() or whatever). You could get the stack trace (ex.ToString()) and remove the 2nd and 3rd lines from the string. If thatโs something youโd like to do and need further help, feel free to ask me by replying to this.