Add back netcoreapp3.1 (#129)

Restore support (plus tests) for the `netcoreapp3.1` target framework.

Author: dellis1972

LibZipSharp.UnitTest/LibZipSharp.UnitTest.csproj

@@ -3,7 +3,7 @@
   <Import Project="$(MSBuildThisFileDirectory)..\LibZipSharp.props" />
 
   <PropertyGroup>
-    <TargetFrameworks>net471;net7.0</TargetFrameworks>
+    <TargetFrameworks>net471;net7.0;netcoreapp3.1</TargetFrameworks>
 
     <IsPackable>false</IsPackable>
     <LibZipSharpBundleAllNativeLibraries>true</LibZipSharpBundleAllNativeLibraries>

LibZipSharp/libZipSharp.csproj

@@ -4,7 +4,7 @@
     <PropertyGroup>
         <AssemblyName>libZipSharp</AssemblyName>
         <AssemblyTitle>libZipSharp</AssemblyTitle>
-        <TargetFrameworks>net7.0;netstandard2.0;net45</TargetFrameworks>
+        <TargetFrameworks>net7.0;netstandard2.0;net45;netcoreapp3.1</TargetFrameworks>
         <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
         <GenerateAssemblyInfo>false</GenerateAssemblyInfo>
         <RootNamespace>Xamarin.Tools.Zip</RootNamespace>

azure-pipelines.yml

@@ -173,7 +173,8 @@ stages:
   - stage: Test
     dependsOn: Build
     variables:
-      DotNetCoreVersion: 7.0.200
+      DotNetCoreVersion: 3.1.201
+      DotNetVersion: 7.0.203
     jobs:
     - job: testlinux
       displayName: 'Test Linux'
@@ -185,6 +186,9 @@ stages:
         - template: yaml-templates/use-dot-net.yaml
           parameters:
             version: $(DotNetCoreVersion)
+        - template: yaml-templates/use-dot-net.yaml
+          parameters:
+            version: $(DotNetVersion)
         - task: DownloadBuildArtifacts@0
           displayName: download artifacts
           inputs:
@@ -211,6 +215,9 @@ stages:
         - template: yaml-templates/use-dot-net.yaml
           parameters:
             version: $(DotNetCoreVersion)
+        - template: yaml-templates/use-dot-net.yaml
+          parameters:
+            version: $(DotNetVersion)
         - task: DownloadBuildArtifacts@0
           displayName: download artifacts
           inputs:
@@ -239,6 +246,9 @@ stages:
         - template: yaml-templates/use-dot-net.yaml
           parameters:
             version: $(DotNetCoreVersion)
+        - template: yaml-templates/use-dot-net.yaml
+          parameters:
+            version: $(DotNetVersion)
         - task: DownloadBuildArtifacts@0
           displayName: download artifacts
           inputs: