[API Proposal]: More helper methods for exception types

[hrrrrustic]

Background and motivation

A few more helper methods that can replace a lot of boring and copy-paste if checks in dotnet/runtime and user code as well.
I believe that this one and #69590 will cover all possible helpers 😸

API Proposal

public class FileNotFoundException
{
    public static void ThrowIfNotExists([NotNull] string? path) {}
}

public class DirectoryNotFoundException
{
    public static void ThrowIfNotExists([NotNull] string? path) {}
}

public class NotSupportedException
{
    public static void ThrowIf(bool condition, string? message = null) {}
}

public class InvalidOperationException
{
   public static void ThrowIf(bool condition, string? message = null) {}
}

API Usage

FileNotFoundException

runtime/src/libraries/System.Diagnostics.FileVersionInfo/src/System/Diagnostics/FileVersionInfo.cs

Lines 274 to 277 in 6ca8c9b

	if (!File.Exists(fileName))
	{
	throw new FileNotFoundException(fileName);
	}

I also saw weird code like this

public void SomeIORelatedMethod(string path)
{
    if (!new FileInfo(path).Exists)
        throw new FileNotFoundException();
}

DirectoryNotFoundException exactly same as previous, File.Exists -> Directory.Exists, new FileInfo -> new DirectoryInfo

NotSupportedException

runtime/src/libraries/System.Net.Mail/src/System/Net/DelegatedStream.cs

Lines 55 to 61 in 6ca8c9b

	get
	{
	if (!CanSeek)
	throw new NotSupportedException(SR.SeekNotSupported);
	return _stream.Length;
	}

There are 15 more absolutely same checks only in this file. Widely used in Stream and Http related classes

InvalidOperationException
I think the only Enumerator types in /runtime have more than thousand lines of code like this

runtime/src/libraries/System.Private.CoreLib/src/System/Collections/Generic/List.cs

Lines 1152 to 1155 in 6ca8c9b

	if (_index == 0 || _index == _list._size + 1)
	{
	ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumOpCantHappen();
	}

Alternative Designs

No response

Risks

No response

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

Tagging subscribers to this area: @dotnet/area-system-runtime
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Background and motivation

A few more helper methods that can replace a lot of boring and copy-paste if checks in dotnet/runtime and user code as well.
I believe that this one and #69590 will cover all possible helpers 😸

API Proposal

public class FileNotFoundException
{
    public static void ThrowIfNotExists([NotNull] string? path) {}
}

public class DirectoryNotFoundException
{
    public static void ThrowIfNotExists([NotNull] string? path) {}
}

public class NotSupportedException
{
    public static void ThrowIf(bool condition, string? message = null) {}
}

public class InvalidOperationException
{
   public static void ThrowIf(bool condition, string? message = null) {}
}

API Usage

FileNotFoundException

runtime/src/libraries/System.Diagnostics.FileVersionInfo/src/System/Diagnostics/FileVersionInfo.cs

Lines 274 to 277 in 6ca8c9b

	if (!File.Exists(fileName))
	{
	throw new FileNotFoundException(fileName);
	}

I also saw weird code like this

public void SomeIORelatedMethod(string path)
{
    if (!new FileInfo(path).Exists)
        throw new FileNotFoundException();
}

DirectoryNotFoundException exactly same as previous, File.Exists -> Directory.Exists, new FileInfo -> new DirectoryInfo

NotSupportedException

runtime/src/libraries/System.Net.Mail/src/System/Net/DelegatedStream.cs

Lines 55 to 61 in 6ca8c9b

	get
	{
	if (!CanSeek)
	throw new NotSupportedException(SR.SeekNotSupported);
	return _stream.Length;
	}

There are 15 more absolutely same checks only in this file. Widely used in Stream and Http related classes

InvalidOperationException
I think the only Enumerator types in /runtime have more than thousand lines of code like this

runtime/src/libraries/System.Private.CoreLib/src/System/Collections/Generic/List.cs

Lines 1152 to 1155 in 6ca8c9b

	if (_index == 0 || _index == _list._size + 1)
	{
	ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumOpCantHappen();
	}

Alternative Designs

No response

Risks

No response

Author:	hrrrrustic
Assignees:	-
Labels:	api-suggestion, area-System.Runtime, untriaged
Milestone:	-

[dakersnar]

This seems worth considering. @tannergooding do you see anything additional needed for this proposal, or know of anyone else I should tag for opinions?

[stephentoub]

The helpers on the argument exceptions, object disposed, etc. are valuable because they're used everywhere. The ones proposed here would seem to have orders of magnitude less use. I'm skeptical they're worth it. They're also more likely to need a customized error message, and in the case of not supported, be used in situations where control flow would still require a separate throw or return.

[jkotas]

string? message = null

Also, customizing message like this is inefficient. This pattern requires the message to be prepared even when the check passes.

[hrrrrustic]

After doing more work on #69590 agree that FileNotFoundException, DirectoryNotFoundException and NotSupportedException are not too commonly used.

Suggesting to discuss only InvalidOperationException. At least as internal helper that could replace some custom helpers (e.g. in List)

string? message = null

Also, customizing message like this is inefficient. This pattern requires the message to be prepared even when the check passes.

WriteIfInterpolatedStringHandler should fix this?