use when and otherwise in csproj

src/ImageSharp/ImageSharp.csproj

@@ -14,13 +14,18 @@
     <Description>A new, fully featured, fully managed, cross-platform, 2D graphics API for .NET</Description>
   </PropertyGroup>
 
-  <PropertyGroup Condition="$(CI) == false" >
-    <TargetFrameworks>netcoreapp3.1;netcoreapp2.1;netstandard2.1;netstandard2.0;netstandard1.3;net472</TargetFrameworks>
-  </PropertyGroup>
-
-  <PropertyGroup Condition="$(CI) == true">
-    <TargetFrameworks>net5.0;netcoreapp3.1;netcoreapp2.1;netstandard2.1;netstandard2.0;netstandard1.3;net472</TargetFrameworks>
-  </PropertyGroup>
+  <Choose>
+    <When Condition="$(CI) == true">
+      <PropertyGroup>
+        <TargetFrameworks>net5.0;netcoreapp3.1;netcoreapp2.1;netstandard2.1;netstandard2.0;netstandard1.3;net472</TargetFrameworks>
+      </PropertyGroup>
+    </When>
+    <Otherwise>
+      <PropertyGroup>
+        <TargetFrameworks>netcoreapp3.1;netcoreapp2.1;netstandard2.1;netstandard2.0;netstandard1.3;net472</TargetFrameworks>
+      </PropertyGroup>
+    </Otherwise>
+  </Choose>
 
   <ItemGroup>
     <None Include="..\..\shared-infrastructure\branding\icons\imagesharp\sixlabors.imagesharp.128.png" Pack="true" PackagePath="" />