Switch to use .NET Standard 2.1 instead of netcoreapp3.0 for broader support

Ix.NET/Source/System.Interactive.Async.Providers/System.Interactive.Async.Providers.csproj

@@ -3,7 +3,7 @@
   <PropertyGroup>
     <Description>Interactive Extensions Async Providers Library used to build query providers and express queries over async enumerable sequences.</Description>
     <AssemblyTitle>Interactive Extensions - Async Providers Library</AssemblyTitle>
-    <TargetFrameworks>net45;net46;netstandard2.0;netcoreapp3.0</TargetFrameworks>
+    <TargetFrameworks>net45;net46;netstandard2.0;netstandard2.1</TargetFrameworks>
     <PackageTags>Ix;Interactive;Extensions;Enumerable;Asynchronous</PackageTags>
   </PropertyGroup>
 

Ix.NET/Source/System.Interactive.Async/System.Interactive.Async.csproj

@@ -3,7 +3,7 @@
   <PropertyGroup>
     <Description>Interactive Extensions Async Library used to express queries over asynchronous enumerable sequences.</Description>
     <AssemblyTitle>Interactive Extensions - Async Library</AssemblyTitle>
-    <TargetFrameworks>net45;net46;netstandard2.0;netcoreapp3.0</TargetFrameworks>
+    <TargetFrameworks>net45;net46;netstandard2.0;netstandard2.1</TargetFrameworks>
     <PackageTags>Ix;Interactive;Extensions;Enumerable;Asynchronous</PackageTags>
   </PropertyGroup>
 

Ix.NET/Source/System.Linq.Async.Queryable/System.Linq.Async.Queryable.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>net45;net46;netstandard2.0;netcoreapp3.0</TargetFrameworks>
+    <TargetFrameworks>net45;net46;netstandard2.0;netstandard2.1</TargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>

Ix.NET/Source/System.Linq.Async/System.Linq.Async.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="MSBuild.Sdk.Extras">
 
   <PropertyGroup>
-    <TargetFrameworks>net45;net46;netstandard2.0;netcoreapp3.0</TargetFrameworks>
+    <TargetFrameworks>net45;net46;netstandard2.0;netstandard2.1</TargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>
@@ -18,7 +18,8 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Condition="'$(TargetFramework)' != 'netcoreapp3.0' " Include="System.Threading.Tasks.Extensions" Version="4.5.2" />
+    <PackageReference Condition="'$(TargetFramework)' != 'netcoreapp3.0' and '$(TargetFramework)' != 'netstandard2.1' "
+                      Include="System.Threading.Tasks.Extensions" Version="4.5.2" />
     <ReferenceAssemblyProjectReference Include="..\refs\System.Linq.Async.Ref\System.Linq.Async.Ref.csproj" />
   </ItemGroup>
 

Ix.NET/Source/refs/Directory.build.props

@@ -3,8 +3,6 @@
   <Import Project="..\Directory.Build.props" />
   
   <PropertyGroup>
-    <!-- This is here so we can create a fake .NET Standard 2.1 facade -->
-    <NETStandardMaximumVersion>2.1</NETStandardMaximumVersion>
     <DefineConstants>$(DefineConstants);REFERENCE_ASSEMBLY</DefineConstants>
   </PropertyGroup>
 

Ix.NET/Source/refs/System.Linq.Async.Ref/System.Linq.Async.Ref.csproj

@@ -4,12 +4,12 @@
     <Description>LINQ Standard Query Operators used to express queries over asynchronous enumerable sequences.</Description>
     <AssemblyTitle>System.Linq.Async</AssemblyTitle>
     <Authors>Microsoft</Authors>
-    <TargetFrameworks>net45;netstandard2.0;netcoreapp3.0</TargetFrameworks>
+    <TargetFrameworks>net45;netstandard2.0;netstandard2.1</TargetFrameworks>
     <PackageTags>Enumerable;Asynchronous;LINQ</PackageTags>
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Condition="'$(TargetFramework)' != 'netcoreapp3.0' "
+    <PackageReference Condition="'$(TargetFramework)' != 'netcoreapp3.0' and '$(TargetFramework)' != 'netstandard2.1' "
                       Include="System.Threading.Tasks.Extensions" Version="4.5.2" />
   </ItemGroup>
 

azure-pipelines.ix.yml

@@ -30,7 +30,7 @@ variables:
 steps:
 - task: DotNetCoreInstaller@0
   inputs:
-    version: '3.0.100-preview4-010374'
+    version: '3.0.100-preview4-010530'
 
 - task: DotNetCoreCLI@2  
   inputs: