Parse double precision using InvariantCulture #2722

stephenquan · 2025-06-16T04:07:43Z

Description of Change

Parse a double using InvariantCulture to avoid issues when CurrentCulture changes, such as to 'ar-AR'.

Linked Issues

Fixes [BUG] MathExpressionConverter doesn't support negative numbers when in Arabic (ar_AR) #2721

PR Checklist

Has a linked Issue, and the Issue has been approved(bug) or Championed (feature/proposal)
Has tests (if omitted, state reason in description)
Has samples (omitted, since this is a minor change)
Rebased on top of main at time of PR
Changes adhere to coding standard
Documentation created or updated: (no change)

Additional information

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VladislavAntonyuk · 2025-06-16T06:02:54Z

src/CommunityToolkit.Maui/Converters/MathExpressionConverter/MathExpression.shared.cs

@@ -362,7 +362,7 @@ bool ParsePrimary()
 		if (ParsePattern(EvaluateNumberPattern()))
 		{
 			string _number = PatternMatch.Groups[1].Value;
-			RPN.Add(new MathToken(MathTokenType.Value, _number, double.Parse(_number)));
+			RPN.Add(new MathToken(MathTokenType.Value, _number, double.Parse(_number, System.Globalization.CultureInfo.InvariantCulture)));


Each converter provides CultureInfo. Maybe it's better to pass it here?

This prevents the ability to use a comma as a decimal separator too.

Perhaps we can make it controllable via a property on the converter instead?

The ParsePattern(EvaluateNumberPattern()) has a regex in it that pretty much assumes US english. The double.Parse() is merely matching it.

If we change it so that it reacts to a passed-in CultureInfo either via the converter (or equivalent), then, I would need to supply a regex for it, else rework how the numbers are being extracted from the string.

@VladislavAntonyuk I tried passing a custom CultureInfo to the converter via XAML but couldn’t find the syntax. It seems the converter uses CultureInfo.CurrentUICulture, which brings us back to the issue, i.e. expressions can fail in certain cultures.

@VladislavAntonyuk @bijington InvariantCulture appears to be used consistently for numeric values in XAML and for numeric expressions in C#. Based on that, I still believe InvariantCulture is the appropriate choice for MathExpressionConverter. After further research, CurrentCulture is generally reserved for UI-facing operations, which doesn't apply to the kind of expressions handled by this converter.

Thanks for the explanation. That's fine with me 👍

Does that mean that I can't use comma as a separator?

@VladislavAntonyuk, the analogy would be to compare it with another double precision XAML property, e.g. VisualElement.Opacity. When one sets that in XAML, don't they also specify that double using InvariantCulture? e.g.

Maui/samples/CommunityToolkit.Maui.Sample/Resources/Styles/Styles.xaml

Line 397 in 2217d08

Opacity=".5"

@VladislavAntonyuk, are you okay with this explanation? I will assume this discussion is resolved.

MartyIX · 2025-06-16T06:05:47Z

src/CommunityToolkit.Maui/Converters/MathExpressionConverter/MathExpression.shared.cs

@@ -362,7 +362,7 @@ bool ParsePrimary()
 		if (ParsePattern(EvaluateNumberPattern()))


It might be good to turn on the CA1305 analyzer in the project to avoid similar bugs.

@MartyIX based on your feedback, I applied the CA1305 analyzer and found multiple conversions in MathExpression.shared.cs that needed updates to satisfy the analyzer. After the changes all unit tests for the math converters still passed.

The CA1305 analyzer also picked up new issues which isn't part of the scope of this PR. Would you like me to create split 3 issues to look? (Camera CA1305, SpeechToText CA1305, Badge CA1305)?

F:\Maui\src\CommunityToolkit.Maui.Camera\CameraInfo.shared.cs(99,4): error CA1305: The behavior of 'StringBuilder.Append(ref StringBuilder.AppendInterpolatedStringHandler)' could vary based on the current user's locale settings. Replace this call in 'CameraInfo.ToString()' with a call to 'StringBuilder.Append(IFormatProvider, ref StringBuilder.AppendInterpolatedStringHandler)'. (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1305) F:\Maui\src\CommunityToolkit.Maui.Camera\CameraInfo.shared.cs(99,4): error CA1305: The behavior of 'StringBuilder.Append(ref StringBuilder.AppendInterpolatedStringHandler)' could vary based on the current user's locale settings. Replace this call in 'CameraInfo.ToString()' with a call to 'StringBuilder.Append(IFormatProvider, ref StringBuilder.AppendInterpolatedStringHandler)'. (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1305) F:\Maui\src\CommunityToolkit.Maui.Camera\CameraInfo.shared.cs(99,4): error CA1305: The behavior of 'StringBuilder.Append(ref StringBuilder.AppendInterpolatedStringHandler)' could vary based on the current user's locale settings. Replace this call in 'CameraInfo.ToString()' with a call to 'StringBuilder.Append(IFormatProvider, ref StringBuilder.AppendInterpolatedStringHandler)'. (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1305) F:\Maui\src\CommunityToolkit.Maui.Camera\CameraInfo.shared.cs(99,4): error CA1305: The behavior of 'StringBuilder.Append(ref StringBuilder.AppendInterpolatedStringHandler)' could vary based on the current user's locale settings. Replace this call in 'CameraInfo.ToString()' with a call to 'StringBuilder.Append(IFormatProvider, ref StringBuilder.AppendInterpolatedStringHandler)'. (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1305) F:\Maui\src\CommunityToolkit.Maui.Camera\CameraInfo.shared.cs(99,4): error CA1305: The behavior of 'StringBuilder.Append(ref StringBuilder.AppendInterpolatedStringHandler)' could vary based on the current user's locale settings. Replace this call in 'CameraInfo.ToString()' with a call to 'StringBuilder.Append(IFormatProvider, ref StringBuilder.AppendInterpolatedStringHandler)'. (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1305) F:\Maui\src\CommunityToolkit.Maui.Core\Essentials\SpeechToText\OfflineSpeechToTextImplementation.android.cs(188,56): error CA1305: The behavior of 'int.ToString()' could vary based on the current user's locale settings. Replace this call in 'RecognitionSupportCallback.OnError(int)' with a call to 'int.ToString(IFormatProvider)'. (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1305) F:\Maui\src\CommunityToolkit.Maui.Core\Essentials\Badge\BadgeImplementation.windows.cs(22,40): error CA1305: The behavior of 'uint.ToString()' could vary based on the current user's locale settings. Replace this call in 'BadgeImplementation.SetCount(uint)' with a call to 'uint.ToString(IFormatProvider)'. (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1305)

Build failed with 7 error(s) and 81 warning(s) in 3.8s

I'm in no position to say what you should do or not, I'm just a random passerby :)) However, I believe it would be a nice new PR or PRs¹ to avoid cramming this PR.

Footnotes

If the number of necessary changes is small, then probably just one PR. ↩

@MartyIX, as per your feedback, I have created a new split issue #2744 to avoid cramming this PR.

You can change the pattern to something like this:

@"^-?\d+[.,]?\d*$"

It should match:

123

-123.45

-123,45

Parse double precision using InvariantCulture

9cc5620

VladislavAntonyuk reviewed Jun 16, 2025

View reviewed changes

MartyIX reviewed Jun 16, 2025

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stephenquan added 4 commits June 18, 2025 22:16

Apply InvariantCulture for object to integer/double/bool conversions

e284fbb

Use shorter InvariantCulture reference

5b53e6c

ConvertToString with InvariantCulture

2b423b8

Add additional unit tests to check string to double coercion

76528a6

stephenquan mentioned this pull request Jun 18, 2025

[BUG] Build errors when turning on the CA1305 analyzer #2744

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Merge branch 'main' into feature/stephenquan/math-ar

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dotnet-policy-service bot added stale The author has not responded in over 30 days help wanted This proposal has been approved and is ready to be implemented labels Jul 24, 2025

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Parse double precision using InvariantCulture #2722

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VladislavAntonyuk Jul 27, 2025 •

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		@@ -362,7 +362,7 @@ bool ParsePrimary()
		if (ParsePattern(EvaluateNumberPattern()))

Parse double precision using InvariantCulture #2722

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Parse double precision using InvariantCulture #2722

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stephenquan commented Jun 16, 2025 •

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