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Numeric format strings: retarget net10.0, add section separators, composite formatting and TryFormat (#2171)
- Retarget both projects from net8.0 to net10.0. - Lift test packages: Microsoft.NET.Test.Sdk 18.9.0, xunit 2.9.3, xunit.runner.visualstudio 4.0.0, coverlet.collector 10.0.1. - CustomFormatStrings: add Accounting, BlankZero and EmptyThirdSection so the semicolon section separator the article now teaches is runnable, including the counter-intuitive case where an empty third section is ignored. - StandardFormatStrings: add FixedPointPrecisionDecimal, Aligned, AlignedInterpolated and TryFormatFixedPoint. - Tests pin the rounding difference between double and decimal under "F2", the composite format item's alignment component, and both TryFormat paths (big enough buffer and too small a buffer). - Tidy: StandardFormatsStrings.cs renamed to StandardFormatStrings.cs (and its test file likewise) to match the class name, and CustomFormatStringsTests moved to the same namespace as the rest of the test project.
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6 files changed

Lines changed: 107 additions & 9 deletions

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‎strings-csharp/StandardAndCustomFormatStrings/StandardAndCustomFormatStrings/CustomFormatStrings.cs‎

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@@ -8,4 +8,7 @@ public static class CustomFormatStrings
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public static string DigitSeparator(double number) => number.ToString("#,###.00");
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public static string Phone(long value) => string.Format("{0:(###) ###-####}", value);
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public static string PhoneInterpolated(long value) => $"{value:(###) ###-####}";
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public static string Accounting(double number) => number.ToString("#,##0.00;(#,##0.00);Zero");
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public static string BlankZero(double number) => number.ToString("0;;''");
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public static string EmptyThirdSection(double number) => number.ToString("#,##0.00;(#,##0.00);");
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}

‎strings-csharp/StandardAndCustomFormatStrings/StandardAndCustomFormatStrings/StandardAndCustomFormatStrings.csproj‎

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@@ -2,7 +2,7 @@
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<PropertyGroup>
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<OutputType>Exe</OutputType>
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<TargetFramework>net8.0</TargetFramework>
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<TargetFramework>net10.0</TargetFramework>
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<ImplicitUsings>enable</ImplicitUsings>
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<Nullable>enable</Nullable>
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</PropertyGroup>

strings-csharp/StandardAndCustomFormatStrings/StandardAndCustomFormatStrings/StandardFormatsStrings.cs renamed to strings-csharp/StandardAndCustomFormatStrings/StandardAndCustomFormatStrings/StandardFormatStrings.cs

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@@ -11,4 +11,10 @@ public static class StandardFormatStrings
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public static string DecimalPrecision(int value) => value.ToString("D5");
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public static string FloatingPointPrecision(double value) => value.ToString("F2");
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public static string Percentage(double value) => $"{value:P2}";
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public static string FixedPointPrecisionDecimal(decimal value) => value.ToString("F2");
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public static string Aligned(double value) => string.Format("{0,12:N2}", value);
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public static string AlignedInterpolated(double value) => $"{value,-12:N2}";
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public static bool TryFormatFixedPoint(double value, Span<char> destination, out int charsWritten) =>
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value.TryFormat(destination, out charsWritten, "F2", CultureInfo.InvariantCulture);
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}

‎strings-csharp/StandardAndCustomFormatStrings/StandardAndCustomFormatStringsTests/CustomFormatStringsTests.cs‎

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namespace StandardAndCustomNumericFormatStringsTests;
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namespace StandardAndCustomFormatStringsTests;
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public class CustomFormatStringsTests
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{
@@ -56,4 +56,35 @@ public void GivenANumber_WhenPhoneInterpolated_ReturnsFormattedPhoneNumber(long
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Assert.Equal(expected, result);
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}
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}
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[Theory]
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[InlineData(1234.5, "1,234.50")]
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[InlineData(-1234.5, "(1,234.50)")]
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[InlineData(0.0, "Zero")]
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public void GivenAValue_WhenAccounting_ThenTheSectionMatchingTheSignIsUsed(double input, string expected)
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{
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string result = CustomFormatStrings.Accounting(input);
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Assert.Equal(expected, result);
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}
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[Theory]
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[InlineData(1234.5, "1235")]
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[InlineData(-1234.5, "-1235")]
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[InlineData(0.0, "")]
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public void GivenAValue_WhenBlankZero_ThenZeroFormatsAsAnEmptyString(double input, string expected)
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{
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string result = CustomFormatStrings.BlankZero(input);
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Assert.Equal(expected, result);
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}
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[Theory]
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[InlineData(0.0, "0.00")]
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public void GivenZero_WhenTheThirdSectionIsEmpty_ThenItIsIgnoredAndTheFirstSectionIsUsed(double input, string expected)
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{
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string result = CustomFormatStrings.EmptyThirdSection(input);
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Assert.Equal(expected, result);
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}
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}

‎strings-csharp/StandardAndCustomFormatStrings/StandardAndCustomFormatStringsTests/StandardAndCustomFormatStringsTests.csproj‎

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<Project Sdk="Microsoft.NET.Sdk">
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<PropertyGroup>
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<TargetFramework>net8.0</TargetFramework>
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<TargetFramework>net10.0</TargetFramework>
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<ImplicitUsings>enable</ImplicitUsings>
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<Nullable>enable</Nullable>
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</PropertyGroup>
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<ItemGroup>
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<PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.6.0" />
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<PackageReference Include="xunit" Version="2.4.2" />
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<PackageReference Include="xunit.runner.visualstudio" Version="2.4.5">
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<PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.9.0" />
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<PackageReference Include="xunit" Version="2.9.3" />
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<PackageReference Include="xunit.runner.visualstudio" Version="4.0.0">
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<IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
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<PrivateAssets>all</PrivateAssets>
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</PackageReference>
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<PackageReference Include="coverlet.collector" Version="6.0.0">
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<PackageReference Include="coverlet.collector" Version="10.0.1">
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<IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
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<PrivateAssets>all</PrivateAssets>
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</PackageReference>

strings-csharp/StandardAndCustomFormatStrings/StandardAndCustomFormatStringsTests/StandardFormatsStringsTests.cs renamed to strings-csharp/StandardAndCustomFormatStrings/StandardAndCustomFormatStringsTests/StandardFormatStringsTests.cs

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@@ -64,4 +64,62 @@ public void GivenANumber_WhenPercentage_ReturnsPercentage(double input, string e
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Assert.Contains(expected, result);
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}
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}
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[Theory]
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[InlineData(1.005, "1.00")]
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[InlineData(0.125, "0.12")]
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public void GivenAnApparentMidpoint_WhenFloatingPointPrecision_ThenTheStoredBinaryValueDecides(double input, string expected)
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{
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string result = StandardFormatStrings.FloatingPointPrecision(input);
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Assert.Equal(expected, result);
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}
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[Fact]
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public void GivenAMidpoint_WhenFixedPointPrecisionDecimal_ThenItRoundsAwayFromZero()
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{
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Assert.Equal("1.01", StandardFormatStrings.FixedPointPrecisionDecimal(1.005m));
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Assert.Equal("0.13", StandardFormatStrings.FixedPointPrecisionDecimal(0.125m));
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}
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[Theory]
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[InlineData(1652.5899, " 1,652.59")]
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public void GivenAValue_WhenAligned_ThenItIsRightAlignedInATwelveCharacterField(double input, string expected)
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{
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string result = StandardFormatStrings.Aligned(input);
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Assert.Equal(expected, result);
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}
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[Theory]
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[InlineData(1652.5899, "1,652.59 ")]
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public void GivenAValue_WhenAlignedInterpolated_ThenANegativeWidthLeftAlignsIt(double input, string expected)
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{
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string result = StandardFormatStrings.AlignedInterpolated(input);
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Assert.Equal(expected, result);
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}
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[Fact]
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public void GivenABigEnoughBuffer_WhenTryFormatFixedPoint_ThenItWritesTheValueAndReturnsTrue()
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{
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Span<char> buffer = stackalloc char[16];
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bool succeeded = StandardFormatStrings.TryFormatFixedPoint(1652.5899, buffer, out int charsWritten);
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Assert.True(succeeded);
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Assert.Equal(7, charsWritten);
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Assert.Equal("1652.59", buffer[..charsWritten].ToString());
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}
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[Fact]
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public void GivenATooSmallBuffer_WhenTryFormatFixedPoint_ThenItWritesNothingAndReturnsFalse()
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{
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Span<char> buffer = stackalloc char[2];
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bool succeeded = StandardFormatStrings.TryFormatFixedPoint(1652.5899, buffer, out int charsWritten);
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Assert.False(succeeded);
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Assert.Equal(0, charsWritten);
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}
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}

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