dotnet · idg10 · Jun 10, 2025 · Jun 10, 2025 · Jun 10, 2025 · Jun 10, 2025
diff --git a/Ix.NET/Source/Ix.NET.sln b/Ix.NET/Source/Ix.NET.sln
@@ -5,7 +5,7 @@ VisualStudioVersion = 17.2.32131.331
 MinimumVisualStudioVersion = 10.0.40219.1
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "test", "test", "{87534290-A7A6-47A4-9A3A-D0D21A9AD1D4}"
 	ProjectSection(SolutionItems) = preProject
-		NetCore31TestReadme.txt = NetCore31TestReadme.txt
+		NetStandard21TestReadme.txt = NetStandard21TestReadme.txt
 	EndProjectSection
 EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution Items", "{B733D97A-F1ED-4FC3-BF8E-9AC47A89DE96}"

diff --git a/Ix.NET/Source/NetCore31TestReadme.txt b/Ix.NET/Source/NetCore31TestReadme.txt
diff --git a/Ix.NET/Source/NetStandard21TestReadme.txt b/Ix.NET/Source/NetStandard21TestReadme.txt
@@ -0,0 +1,5 @@
+Ix.NET 6.0 offers a .NET Standard 2.1 target, but currently, we have no way of testing this.
+
+We used to test this target by running tests in .NET Core 3.1. Unfortunately, the test runners now crash when running tests in .NET Core 3.1. .NET Core 3.1 has long since been out of support, so there's not much we can do about this. (It now reports the absence of ssllib on the hosted build agents.)
+
+Although current versions of .NET (but not .NET Framework) support .NET Standard 2.1, they are all going to prefer the net6.0 target. It might be possible to test via Mono instead, or possibly even Unity, but this would likely involve additional CI/CD work. But for now this target is untested. If we can't find a way to test netstandard2.1, that suggests there's no scenario in which it is useful now, so we may remove it in a future release.
diff --git a/.../System.Interactive.Async.Providers.Tests/System.Interactive.Async.Providers.Tests.csproj b/.../System.Interactive.Async.Providers.Tests/System.Interactive.Async.Providers.Tests.csproj
@@ -1,8 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <!-- See NetCore31TestReadme.txt for why we still use netcoreapp3.1 -->
-    <TargetFrameworks>net48;net8.0;net6.0;netcoreapp3.1</TargetFrameworks>
+    <TargetFrameworks>net48;net8.0;net6.0</TargetFrameworks>
     <NoWarn>$(NoWarn);CS0618</NoWarn>
   </PropertyGroup>
 

diff --git a/Ix.NET/Source/System.Interactive.Async.Tests/System.Interactive.Async.Tests.csproj b/Ix.NET/Source/System.Interactive.Async.Tests/System.Interactive.Async.Tests.csproj
@@ -1,8 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <!-- See NetCore31TestReadme.txt for why we still use netcoreapp3.1 -->
-    <TargetFrameworks>net48;net8.0;net6.0;netcoreapp3.1</TargetFrameworks>
+    <TargetFrameworks>net48;net8.0;net6.0</TargetFrameworks>
 
     <!--
       CA1510: Use ArgumentNullException.ThrowIfNull - not available on .NET 4.8

diff --git a/Ix.NET/Source/System.Interactive.Async.Tests/System/Linq/Operators/Distinct.cs b/Ix.NET/Source/System.Interactive.Async.Tests/System/Linq/Operators/Distinct.cs
@@ -41,8 +41,9 @@ public async Task Distinct6()
         {
             var xs = new[] { 1, 2, 1, 3, 5, 2, 1, 4 }.ToAsyncEnumerable().Distinct(k => k);
 
-            var res = new[] { 1, 2, 3, 5, 4 };
-            Assert.True(res.SequenceEqual(await xs.ToArrayAsync()));
+            var expected = new[] { 1, 2, 3, 5, 4 };
+            var actual = await xs.ToArrayAsync();
+            Assert.True(expected.SequenceEqual(actual));
         }
 
         [Fact]

diff --git a/Ix.NET/Source/System.Interactive.Tests/System.Interactive.Tests.csproj b/Ix.NET/Source/System.Interactive.Tests/System.Interactive.Tests.csproj
@@ -1,8 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <!-- See NetCore31TestReadme.txt for why we still use netcoreapp3.1 -->
-    <TargetFrameworks>net48;net8.0;net6.0;netcoreapp3.1</TargetFrameworks>
+    <TargetFrameworks>net48;net8.0;net6.0</TargetFrameworks>
 
     <!--
       CA1822: Make member static. Not necessary for test code.

diff --git a/Ix.NET/Source/System.Linq.Async.Queryable.Tests/System.Linq.Async.Queryable.Tests.csproj b/Ix.NET/Source/System.Linq.Async.Queryable.Tests/System.Linq.Async.Queryable.Tests.csproj
@@ -1,8 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <!-- See NetCore31TestReadme.txt for why we still use netcoreapp3.1 -->
-    <TargetFrameworks>net48;net8.0;net6.0;netcoreapp3.1</TargetFrameworks>
+    <TargetFrameworks>net48;net8.0;net6.0</TargetFrameworks>
     <NoWarn>$(NoWarn);CS0618</NoWarn>
   </PropertyGroup>
 

diff --git a/Ix.NET/Source/System.Linq.Async.Tests/System.Linq.Async.Tests.csproj b/Ix.NET/Source/System.Linq.Async.Tests/System.Linq.Async.Tests.csproj
@@ -1,8 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <!-- See NetCore31TestReadme.txt for why we still use netcoreapp3.1 -->
-    <TargetFrameworks>net48;net8.0;net6.0;netcoreapp3.1</TargetFrameworks>
+    <TargetFrameworks>net48;net8.0;net6.0</TargetFrameworks>
 
     <!--
     CA1510: Use ArgumentNullException.ThrowIfNull - not available on .NET 4.8

diff --git a/Ix.NET/Source/System.Linq.Async.Tests/System/Linq/Operators/Concat.cs b/Ix.NET/Source/System.Linq.Async.Tests/System/Linq/Operators/Concat.cs
@@ -104,8 +104,9 @@ public async Task Concat_Three_ToArray()
 
             var c = xs.Concat(ys).Concat(zs);
 
-            var res = new[] { 1, 2, 3, 4, 5, 6, 7, 8 };
-            Assert.True(res.SequenceEqual(await c.ToArrayAsync()));
+            var expected = new[] { 1, 2, 3, 4, 5, 6, 7, 8 };
+            var actual = await c.ToArrayAsync();
+            Assert.True(expected.SequenceEqual(actual));
         }
 
         [Fact]

diff --git a/Ix.NET/Source/System.Linq.Async.Tests/System/Linq/Operators/DefaultIfEmpty.cs b/Ix.NET/Source/System.Linq.Async.Tests/System/Linq/Operators/DefaultIfEmpty.cs
@@ -136,9 +136,10 @@ public async Task DefaultIfEmpty_IAsyncIListProvider_ToArray_Empty()
         {
             var xs = AsyncEnumerable.Empty<int>().DefaultIfEmpty(42);
 
-            var res = new[] { 42 };
+            var expected = new[] { 42 };
+            var actual = await xs.ToArrayAsync();
 
-            Assert.True(res.SequenceEqual(await xs.ToArrayAsync()));
+            Assert.True(expected.SequenceEqual(actual));
         }
 
         [Fact]
@@ -156,9 +157,10 @@ public async Task DefaultIfEmpty_IAsyncIListProvider_ToList()
         {
             var xs = new[] { 1, 2, 3, 4 }.ToAsyncEnumerable().DefaultIfEmpty();
 
-            var res = new[] { 1, 2, 3, 4 };
+            var expected = new[] { 1, 2, 3, 4 };
 
-            Assert.True(res.SequenceEqual(await xs.ToArrayAsync()));
+            var actual = await xs.ToArrayAsync();
+            Assert.True(expected.SequenceEqual(actual));
         }
 
         [Fact]

diff --git a/Ix.NET/Source/System.Linq.Async.Tests/System/Linq/Operators/Distinct.cs b/Ix.NET/Source/System.Linq.Async.Tests/System/Linq/Operators/Distinct.cs
@@ -52,8 +52,9 @@ public async Task Distinct_ToArray()
         {
             var xs = new[] { 1, 2, 1, 3, 5, 2, 1, 4 }.ToAsyncEnumerable().Distinct();
 
-            var res = new[] { 1, 2, 3, 5, 4 };
-            Assert.True(res.SequenceEqual(await xs.ToArrayAsync()));
+            var expected = new[] { 1, 2, 3, 5, 4 };
+            var actual = await xs.ToArrayAsync();
+            Assert.True(expected.SequenceEqual(actual));
         }
 
         [Fact]

diff --git a/Ix.NET/Source/System.Linq.Async.Tests/System/Linq/Operators/OrderBy.Generated.cs b/Ix.NET/Source/System.Linq.Async.Tests/System/Linq/Operators/OrderBy.Generated.cs
@@ -7498,8 +7498,10 @@ public async Task OrderBy_OrderByDescendingAsyncWithCancellation_ThenByDescendin
         private async Task AssertSorted<T>(IAsyncEnumerable<T> asyncRes, IEnumerable<T> syncRes)
         {
             Assert.True(await syncRes.ToAsyncEnumerable().SequenceEqualAsync(asyncRes));
-            Assert.True(syncRes.ToList().SequenceEqual(await asyncRes.ToListAsync()));
-            Assert.True(syncRes.ToArray().SequenceEqual(await asyncRes.ToArrayAsync()));
+            var toListResult = await asyncRes.ToListAsync();
+            Assert.True(syncRes.ToList().SequenceEqual(toListResult));
+            var toArrayResult = await asyncRes.ToArrayAsync();
+            Assert.True(syncRes.ToArray().SequenceEqual(toArrayResult));
 
             int syncCount = syncRes.Count();
             int asyncCount = await asyncRes.CountAsync();

diff --git a/azure-pipelines.ix.yml b/azure-pipelines.ix.yml
@@ -29,7 +29,7 @@ stages:
   jobs:
   - job: Build
     pool:
-      vmImage: ubuntu-latest
+      vmImage: windows-latest
     steps:
     - task: UseDotNet@2
       displayName: Use .NET Core 8.x SDK
@@ -42,20 +42,14 @@ stages:
         version: '6.x'
         packageType: runtime
 
-    - task: UseDotNet@2
-      displayName: .NET Core 3.1 runtime
-      inputs:
-        version: '3.1.x'
-        packageType: runtime
-
     - task: DotNetCoreCLI@2
       inputs:
         command: custom
         custom: tool
         arguments: install --tool-path . nbgv
       displayName: Install NBGV tool
 
-    - script: ./nbgv cloud -p Ix.NET/Source
+    - script: nbgv cloud -a -p Ix.NET/Source
       displayName: Set Version
 
     - task: DotNetCoreCLI@2
@@ -97,7 +91,7 @@ stages:
         arguments: -c $(BuildConfiguration) --settings Ix.NET/Source/CodeCoverage.runsettings --collect:"XPlat Code Coverage" -- RunConfiguration.DisableAppDomain=true
       displayName: Run Tests
 
-    - script: ./reportgenerator -reports:$(Agent.TempDirectory)/**/coverage.cobertura.xml -targetdir:$(Build.SourcesDirectory)/Ix.NET/Source/coverlet/reports -reporttypes:"Cobertura"
+    - script: reportgenerator -reports:$(Agent.TempDirectory)/**/coverage.cobertura.xml -targetdir:$(Build.SourcesDirectory)/Ix.NET/Source/coverlet/reports -reporttypes:"Cobertura"
       displayName: Create reports
 
     - task: PublishCodeCoverageResults@1