add properties for api diff versions and package locations.

build/ApiDiff.props

@@ -1,7 +1,10 @@
 <Project DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
-  <ItemGroup>
-    <PackageDownload Include="Avalonia" Version="[0.10.0-preview1]" />
-    <PackageReference Include="Microsoft.DotNet.ApiCompat" Version="5.0.0-beta.20364.3" PrivateAssets="All" />
-    <ResolvedMatchingContract Include="$(NuGetPackageRoot)\avalonia\0.10.0-preview1\lib\netstandard2.0\$(AssemblyName).dll" />
-  </ItemGroup>
+  <PropertyGroup>
+    <ApiContractPackageVersion>0.10.0-preview1</ApiContractPackageVersion>
+  </PropertyGroup>
+    <ItemGroup>
+      <PackageDownload Include="Avalonia" Version="[$(ApiContractPackageVersion)]" />
+      <PackageReference Include="Microsoft.DotNet.ApiCompat" Version="5.0.0-beta.20364.3" PrivateAssets="All" />
+      <ResolvedMatchingContract Include="$(NuGetPackageRoot)\$(NugetPackageName)\$(ApiContractPackageVersion)\lib\netstandard2.0\$(AssemblyName).dll" />
+    </ItemGroup>
 </Project>

src/Avalonia.Base/Avalonia.Base.csproj

@@ -4,6 +4,7 @@
     <AssemblyName>Avalonia.Base</AssemblyName>
     <RootNamespace>Avalonia</RootNamespace>
     <AllowUnsafeBlocks>True</AllowUnsafeBlocks>
+    <NugetPackageName>Avalonia</NugetPackageName>
   </PropertyGroup>
   <ItemGroup>
     <ProjectReference Include="..\Avalonia.Build.Tasks\Avalonia.Build.Tasks.csproj"/>

src/Avalonia.Controls/Avalonia.Controls.csproj

@@ -1,6 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <TargetFramework>netstandard2.0</TargetFramework>
+    <NugetPackageName>Avalonia</NugetPackageName>
   </PropertyGroup>
   <ItemGroup>
     <ProjectReference Include="..\Avalonia.Animation\Avalonia.Animation.csproj" />
@@ -14,4 +15,5 @@
   </ItemGroup>
   <Import Project="..\..\build\Rx.props" />
   <Import Project="..\..\build\JetBrains.Annotations.props" />
+  <Import Project="..\..\build\ApiDiff.props" />
 </Project>