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Merged
vladimir-pecanac-main merged 2 commits into from
Oct 14, 2026
Merged

Declare an Empty Array in C#: .NET 10, collection expression, stronger tests #2288

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Declare an empty array in C#: .NET 10, collection expression, tests a…
vladimir-pecanac-main Oct 11, 2026
cc7f6db
Merge branch 'main' into seo/86365-csharp-how-to-declare-an-empty-array
vladimir-pecanac-main Oct 14, 2026
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79 changes: 40 additions & 39 deletions collections-arrays/DeclareAnEmptyStringArrayInCSharp/EmptyStringArrayFactory/ArrayFactory.cs
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Original file line number Diff line number Diff line change
@@ -1,42 +1,43 @@
namespace EmptyStringArrayFactory
namespace EmptyStringArrayFactory;

public class ArrayFactory
{
public class ArrayFactory
public static string[] CreateWithNewAndZeroLength()
{
return new string[0];
}

public static string[] CreateWithEmptyInitializer()
{
return new string[] { };
}

public static string[] CreateWithImplicitInitializer()
{
string[] myArray = { };

return myArray;
}

public static string[] CreateWithEnumerableEmpty()
{
public static string[] CreateEmptyArrayExample1()
{
return new string[0];
}

public static string[] CreateEmptyArrayExample2()
{
return new string[] { };
}

public static string[] CreateEmptyArrayExample3()
{
string[] myArray = { };

return myArray;
}

public static string[] CreateEmptyArrayExample4()
{
return Enumerable.Empty<string>().ToArray();
}

public static string[] CreateEmptyArrayExample5()
{
return Enumerable.Repeat("", 0).ToArray();
}

public static string[] CreateEmptyArrayExample6()
{
return Enumerable.Repeat(string.Empty, 0).ToArray();
}

public static string[] CreateEmptyArrayExample7()
{
return Array.Empty<string>();
}
return Enumerable.Empty<string>().ToArray();
}
}

public static string[] CreateWithEnumerableRepeatEmptyString()
{
return Enumerable.Repeat("", 0).ToArray();
}

public static string[] CreateWithEnumerableRepeatStringEmpty()
{
return Enumerable.Repeat(string.Empty, 0).ToArray();
}

public static string[] CreateWithArrayEmpty()
{
return Array.Empty<string>();
}

public static string[] CreateEmptyArrayWithCollectionExpression() => [];
}
2 changes: 1 addition & 1 deletion .../DeclareAnEmptyStringArrayInCSharp/EmptyStringArrayFactory/EmptyStringArrayFactory.csproj
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
<Project Sdk="Microsoft.NET.Sdk">

<PropertyGroup>
<TargetFramework>net7.0</TargetFramework>
<TargetFramework>net10.0</TargetFramework>
<ImplicitUsings>enable</ImplicitUsings>
<Nullable>enable</Nullable>
</PropertyGroup>
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55 changes: 39 additions & 16 deletions collections-arrays/DeclareAnEmptyStringArrayInCSharp/Tests/ArrayUnitTest.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,69 +3,92 @@ namespace Tests
{
public class ArrayUnitTest
{
private readonly int _expectedSize = 0;
[Fact]
public void WhenCreateWithNewAndZeroLengthIsCalled_ThenReturnAnEmptyStringArray()
{
var actual = ArrayFactory.CreateWithNewAndZeroLength();

Assert.NotNull(actual);
Assert.IsType<string[]>(actual);
Assert.Empty(actual);
}

[Fact]
public void WhenCreateEmptyArrayExample1IsCalled_ThenReturnAnEmptyStringArray()
public void WhenCreateWithEmptyInitializerIsCalled_ThenReturnAnEmptyStringArray()
{
var actual = ArrayFactory.CreateEmptyArrayExample1();
var actual = ArrayFactory.CreateWithEmptyInitializer();

Assert.NotNull(actual);
Assert.IsType<string[]>(actual);
Assert.Empty(actual);
}

[Fact]
public void WhenCreateEmptyArrayExample2IsCalled_ThenReturnAnEmptyStringArray()
public void WhenCreateWithImplicitInitializerIsCalled_ThenReturnAnEmptyStringArray()
{
var actual = ArrayFactory.CreateEmptyArrayExample2();
var actual = ArrayFactory.CreateWithImplicitInitializer();

Assert.NotNull(actual);
Assert.IsType<string[]>(actual);
Assert.Empty(actual);
}

[Fact]
public void WhenCreateEmptyArrayExample3IsCalled_ThenReturnAnEmptyStringArray()
public void WhenCreateWithEnumerableEmptyIsCalled_ThenReturnAnEmptyStringArray()
{
var actual = ArrayFactory.CreateEmptyArrayExample3();
var actual = ArrayFactory.CreateWithEnumerableEmpty();

Assert.NotNull(actual);
Assert.IsType<string[]>(actual);
Assert.Empty(actual);
}

[Fact]
public void WhenCreateEmptyArrayExample4IsCalled_ThenReturnAnEmptyStringArray()
public void WhenCreateWithEnumerableRepeatEmptyStringIsCalled_ThenReturnAnEmptyStringArray()
{
var actual = ArrayFactory.CreateEmptyArrayExample4();
var actual = ArrayFactory.CreateWithEnumerableRepeatEmptyString();

Assert.NotNull(actual);
Assert.IsType<string[]>(actual);
Assert.Empty(actual);
}

[Fact]
public void WhenCreateEmptyArrayExample5IsCalled_ThenReturnAnEmptyStringArray()
public void WhenCreateWithEnumerableRepeatStringEmptyIsCalled_ThenReturnAnEmptyStringArray()
{
var actual = ArrayFactory.CreateEmptyArrayExample5();
var actual = ArrayFactory.CreateWithEnumerableRepeatStringEmpty();

Assert.NotNull(actual);
Assert.IsType<string[]>(actual);
Assert.Empty(actual);
}

[Fact]
public void WhenCreateEmptyArrayExample6IsCalled_ThenReturnAnEmptyStringArray()
public void WhenCreateWithArrayEmptyIsCalled_ThenReturnAnEmptyStringArray()
{
var actual = ArrayFactory.CreateEmptyArrayExample6();
var actual = ArrayFactory.CreateWithArrayEmpty();

Assert.NotNull(actual);
Assert.IsType<string[]>(actual);
Assert.Empty(actual);
}

[Fact]
public void WhenCreateEmptyArrayExample7IsCalled_ThenReturnAnEmptyStringArray()
public void WhenCreateEmptyArrayWithCollectionExpressionIsCalled_ThenReturnAnEmptyStringArray()
{
var actual = ArrayFactory.CreateEmptyArrayExample7();
var actual = ArrayFactory.CreateEmptyArrayWithCollectionExpression();

Assert.NotNull(actual);
Assert.IsType<string[]>(actual);
Assert.Empty(actual);
}

[Fact]
public void WhenCreateWithArrayEmptyIsCalledTwice_ThenBothCallsReturnTheSameInstance() =>
Assert.Same(ArrayFactory.CreateWithArrayEmpty(), ArrayFactory.CreateWithArrayEmpty());

[Fact]
public void WhenCreateWithCollectionExpressionIsCalled_ThenItReturnsTheArrayEmptyInstance() =>
Assert.Same(Array.Empty<string>(), ArrayFactory.CreateEmptyArrayWithCollectionExpression());
}
}
}
10 changes: 5 additions & 5 deletions collections-arrays/DeclareAnEmptyStringArrayInCSharp/Tests/Tests.csproj
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
<Project Sdk="Microsoft.NET.Sdk">

<PropertyGroup>
<TargetFramework>net7.0</TargetFramework>
<TargetFramework>net10.0</TargetFramework>
<ImplicitUsings>enable</ImplicitUsings>
<Nullable>enable</Nullable>

Expand All @@ -10,13 +10,13 @@
</PropertyGroup>

<ItemGroup>
<PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.3.2" />
<PackageReference Include="xunit" Version="2.4.2" />
<PackageReference Include="xunit.runner.visualstudio" Version="2.4.5">
<PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.10.1" />
<PackageReference Include="xunit" Version="2.9.3" />
<PackageReference Include="xunit.runner.visualstudio" Version="4.0.1">
<IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
<PrivateAssets>all</PrivateAssets>
</PackageReference>
<PackageReference Include="coverlet.collector" Version="3.1.2">
<PackageReference Include="coverlet.collector" Version="10.1.0">
<IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
<PrivateAssets>all</PrivateAssets>
</PackageReference>
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