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Merged
Tyrrrz merged 3 commits into from
Mar 17, 2026
Merged

Add missing string.Join polyfills #90

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334ad9c
Initial plan
Copilot Mar 17, 2026
ce21ea0
Add missing string.Join polyfills for NetCore10 and NetCore20
Copilot Mar 17, 2026
22a38e0
Address review feedback: remove untestable NetCore10 tests, merge ext…
Copilot Mar 17, 2026
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42 changes: 42 additions & 0 deletions PolyShim.Tests/NetCore20/StringTests.cs
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Expand Up @@ -129,4 +129,46 @@ public void Split_String_Count_Test()
str.Split(" ", 2).Should().Equal("a", "b c");
str.Split(" ", 1).Should().Equal("a b c");
}

[Fact]
public void Join_CharSeparator_ObjectArray_Test()
{
// Act & assert
string.Join(',', new object?[] { 1, "two", 3.0 }).Should().Be("1,two,3");
string.Join(',', new object?[] { }).Should().Be("");
string.Join(',', new object?[] { null, "a", null }).Should().Be(",a,");
}

[Fact]
public void Join_CharSeparator_StringArray_Test()
{
// Act & assert
string.Join(',', "a", "b", "c").Should().Be("a,b,c");
string.Join(',', new string?[] { }).Should().Be("");
string.Join(',', new string?[] { null, "a", null }).Should().Be(",a,");
}

[Fact]
public void Join_CharSeparator_EnumerableT_Test()
{
// Act & assert
string.Join(',', new System.Collections.Generic.List<int> { 1, 2, 3 })
.Should()
.Be("1,2,3");
string.Join(',', new System.Collections.Generic.List<string?> { "a", null, "b" })
.Should()
.Be("a,,b");
}

[Fact]
public void Join_CharSeparator_WithIndexAndCount_Test()
{
// Arrange
var values = new string?[] { "a", "b", "c", "d" };

// Act & assert
string.Join(',', values, 1, 2).Should().Be("b,c");
string.Join(',', values, 0, 4).Should().Be("a,b,c,d");
string.Join(',', values, 2, 0).Should().Be("");
}
}
9 changes: 9 additions & 0 deletions PolyShim/NetCore10/String.cs
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Expand Up @@ -6,6 +6,7 @@
// ReSharper disable PartialTypeWithSinglePart

using System;
using System.Collections.Generic;
using System.Linq;
using System.Diagnostics.CodeAnalysis;

Expand All @@ -19,6 +20,14 @@ internal static class MemberPolyfills_NetCore10_String
// https://learn.microsoft.com/dotnet/api/system.string.isnullorwhitespace
public static bool IsNullOrWhiteSpace(string? value) =>
value is null || value.All(char.IsWhiteSpace);

// https://learn.microsoft.com/dotnet/api/system.string.join#system-string-join(system-string-system-object())
public static string Join(string? separator, params object?[] values) =>
string.Join(separator, values.Select(v => v?.ToString()).ToArray());

// https://learn.microsoft.com/dotnet/api/system.string.join#system-string-join-1(system-string-system-collections-generic-ienumerable((-0)))
public static string Join<T>(string? separator, IEnumerable<T> values) =>
string.Join(separator, values.Select(v => ((object?)v)?.ToString()).ToArray());
}
}
#endif
21 changes: 21 additions & 0 deletions PolyShim/NetCore20/String.cs
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Expand Up @@ -6,7 +6,9 @@
// ReSharper disable PartialTypeWithSinglePart

using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Text;
using System.Diagnostics.CodeAnalysis;

Expand Down Expand Up @@ -140,6 +142,25 @@ public string[] Split(
string? separator,
StringSplitOptions options = StringSplitOptions.None
) => str.Split([separator ?? ""], options);

// https://learn.microsoft.com/dotnet/api/system.string.join#system-string-join(system-char-system-object())
public static string Join(char separator, params object?[] values) =>
string.Join(separator.ToString(), values.Select(v => v?.ToString()).ToArray());

// https://learn.microsoft.com/dotnet/api/system.string.join#system-string-join(system-char-system-string())
public static string Join(char separator, params string?[] values) =>
string.Join(separator.ToString(), values);

// https://learn.microsoft.com/dotnet/api/system.string.join#system-string-join-1(system-char-system-collections-generic-ienumerable((-0)))
public static string Join<T>(char separator, IEnumerable<T> values) =>
string.Join(
separator.ToString(),
values.Select(v => ((object?)v)?.ToString()).ToArray()
);

// https://learn.microsoft.com/dotnet/api/system.string.join#system-string-join(system-char-system-string()-system-int32-system-int32)
public static string Join(char separator, string?[] value, int startIndex, int count) =>
string.Join(separator.ToString(), value, startIndex, count);
}
}
#endif
10 changes: 8 additions & 2 deletions PolyShim/Signatures.md
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@@ -1,8 +1,8 @@
# Signatures

- **Total:** 373
- **Total:** 379
- **Types:** 79
- **Members:** 294
- **Members:** 300

___

Expand Down Expand Up @@ -371,6 +371,12 @@ ___
- [`bool IsNullOrWhiteSpace(string?)`](https://learn.microsoft.com/dotnet/api/system.string.isnullorwhitespace) <sup><sub>.NET Core 1.0</sub></sup>
- [`bool StartsWith(char)`](https://learn.microsoft.com/dotnet/api/system.string.startswith#system-string-startswith(system-char)) <sup><sub>.NET Core 2.0</sub></sup>
- [`int GetHashCode(StringComparison)`](https://learn.microsoft.com/dotnet/api/system.string.gethashcode#system-string-gethashcode(system-stringcomparison)) <sup><sub>.NET Core 2.0</sub></sup>
- [`string Join(char, params object?[])`](https://learn.microsoft.com/dotnet/api/system.string.join#system-string-join(system-char-system-object())) <sup><sub>.NET Core 2.0</sub></sup>
- [`string Join(char, params string?[])`](https://learn.microsoft.com/dotnet/api/system.string.join#system-string-join(system-char-system-string())) <sup><sub>.NET Core 2.0</sub></sup>
- [`string Join(char, string?[], int, int)`](https://learn.microsoft.com/dotnet/api/system.string.join#system-string-join(system-char-system-string()-system-int32-system-int32)) <sup><sub>.NET Core 2.0</sub></sup>
- [`string Join(string?, params object?[])`](https://learn.microsoft.com/dotnet/api/system.string.join#system-string-join(system-string-system-object())) <sup><sub>.NET Core 1.0</sub></sup>
- [`string Join<T>(char, IEnumerable<T>)`](https://learn.microsoft.com/dotnet/api/system.string.join#system-string-join-1(system-char-system-collections-generic-ienumerable((-0)))) <sup><sub>.NET Core 2.0</sub></sup>
- [`string Join<T>(string?, IEnumerable<T>)`](https://learn.microsoft.com/dotnet/api/system.string.join#system-string-join-1(system-string-system-collections-generic-ienumerable((-0)))) <sup><sub>.NET Core 1.0</sub></sup>
- [`string Replace(string, string?, bool, CultureInfo?)`](https://learn.microsoft.com/dotnet/api/system.string.replace#system-string-replace(system-string-system-string-system-boolean-system-globalization-cultureinfo)) <sup><sub>.NET Core 2.0</sub></sup>
- [`string Replace(string, string?, StringComparison)`](https://learn.microsoft.com/dotnet/api/system.string.replace#system-string-replace(system-string-system-string-system-stringcomparison)) <sup><sub>.NET Core 2.0</sub></sup>
- [`string ReplaceLineEndings()`](https://learn.microsoft.com/dotnet/api/system.string.replacelineendings#system-string-replacelineendings) <sup><sub>.NET 6.0</sub></sup>
Expand Down
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