Encode String to Base64 in MSBuild - msbuild

Question

I want to convert a string to base64 within a msbuild target but msbuild tells me the type convert is not available.
<ItemGroup>
<Headers Include="Authorization">
<Content>$([Convert]::ToBase64String("user:password"))</Content>
</Headers>
</ItemGroup>
Can somone help me?
EDIT:
Found a solution I don't like:
<UsingTask TaskName="ToBase64" TaskFactory="CodeTaskFactory" AssemblyFile="$(MSBuildToolsPath)\Microsoft.Build.Tasks.v4.0.dll" >
<ParameterGroup>
<In ParameterType="System.String" Required="true" />
<Out ParameterType="System.String" Output="true" />
</ParameterGroup>
<Task>
<Code Type="Fragment" Language="cs">
Out = System.Convert.ToBase64String(System.Text.Encoding.Default.GetBytes(In));
</Code>
</Task>
</UsingTask>
<Target Name="WebRequest">
<ToBase64 In="$(auth)">
<Output PropertyName="authBase64" TaskParameter="Out" />
</ToBase64>
</Target>
Is there a better way?

Answer 1

You cannot use MSBuild property functions to do whatever you want. There are some limitations and one is that only a few namespace can be used. You have the whole list here : http://blogs.msdn.com/b/visualstudio/archive/2010/04/02/msbuild-property-functions.aspx
Your problem is that you need the System.Text.Encoding namespace (to get the bytes array of your string) which is not supported.
As a proof :
<ItemGroup>
<Headers Include="Authorization">
<Content>$([System.Convert]::ToBase64String($([System.Text.Encoding]::Default.GetBytes("user:password"))))</Content>
</Headers>
</ItemGroup>
<Target Name="Deploy" >
<Message Text="#(Headers->'%(Content)')" Importance="high" />
</Target>
fails with error MSB4185: The function "Default" on type "System.Text.Encoding" is not available for execution as an MSBuild property function.
but if you set the environment variable MSBUILDENABLEALLPROPERTYFUNCTIONS=1 then it succeeds :
D:\set MSBUILDENABLEALLPROPERTYFUNCTIONS=1
D:\>c:\windows\Microsoft.NET\Framework64\v4.0.30319\MSBuild.exe test.proj
Project "D:\test.proj" on node 1 (default targets).
Deploy:
dXNlcjpwYXNzd29yZA==
Done Building Project "D:\test.proj" (default targets).
For maintenance reasons, I would recommend you stick with your verbose task approach as this environment variable is not supported.

Answer 2

Since April 2022 support to encode/Decode Base64 is directly integrated into msbuild:
https://github.com/dotnet/msbuild/pull/7554
$([MSBuild]::ConvertToBase64("text"))