Identify if a string is a number: .NET 10, empty-string guard, stricter double check

[vladimir-pecanac-main]

Sample update for the article "How to Check If a String Is a Number in C#" (https://code-maze.com/csharp-identify-if-a-string-is-a-number/). Only strings-csharp/IdentifyIfStringIsANumber changes.

Changes

• All three projects retargeted from net7.0 to net10.0.
• UsingCharIsDigit, UsingCharIsDigitWithForeach and UsingCharIsBetween09 returned true for an empty string, because All() over an empty sequence is true and a foreach over an empty string never runs its body. Each now returns false for null or empty input. Every theory gains an [InlineData("", false)] row, so the suite goes from 42 to 49 tests.
• DoubleTryParse switches from NumberStyles.Any to NumberStyles.Float | NumberStyles.AllowThousands with CultureInfo.InvariantCulture kept. NumberStyles.Any accepted "(5)" (accounting notation) as a number; the article never explains that style, and no test covered the line.
• Program.cs: the "Using Char.IdDigit:" label is fixed and the program now prints all seven approaches instead of four.
• BenchmarkRunner: a [Params] input "a12345678" (fails on its first character) runs next to "123456789", so the early-exit advantage of the loops is measured.

Packages (re-queried on NuGet 2026-10-09)

• Microsoft.NET.Test.Sdk 17.5.0 to 18.10.1
• xunit 2.4.2 to 2.9.3
• xunit.runner.visualstudio 2.4.5 to 4.0.0
• coverlet.collector 3.2.0 to 10.1.0
• BenchmarkDotNet 0.13.5 to 0.15.8

Verification on .NET SDK 10.0.302, runtime 10.0.10, Windows 10.0.19045

• dotnet build -c Release: 0 warnings, 0 errors
• dotnet test -c Release: 49 passed, 0 failed
• dotnet list package --vulnerable --include-transitive: no vulnerable packages in any project
• BenchmarkDotNet run: 14 benchmarks, completed