Assemebly

We can store a GIT version hash or a time stamp in the assembly during build time and read the data later at runtime.

Example:

<!-- *.csproj -->
<Project Sdk="Microsoft.NET.Sdk">
    <Target Name="SetSourceRevisionId" BeforeTargets="InitializeSourceControlInformation">
        <Exec Command="git describe --long --always" ConsoleToMSBuild="True" IgnoreExitCode="False">
            <Output PropertyName="SourceRevisionId" TaskParameter="ConsoleOutput" />
        </Exec>
        <ItemGroup>
            <!-- e.g. store in existing metadata -->
            <AssemblyMetadata Include="SourceRevisionId" Value="$(SourceRevisionId)" />
            <!-- or store in custom attribute -->
            <AssemblyAttribute Include="My.Namespace.MyGitHashAttribute">
                <_Parameter1>$(SourceRevisionId)</_Parameter1>
            </AssemblyAttribute>
            <!-- Also possible with timestamp -->  
            <AssemblyMetadata Include="BuiltAt" Value="$([System.DateTime]::UtcNow.ToString('yyyy-MM-dd HH:mm:ss'))" />
            </AssemblyAttribute>
        </ItemGroup>
    </Target>       
</Project>

This data get stored in the build assembly. e.g:

// ...
using System;
using System.Reflection;

// Metadata
[assembly: System.Reflection.AssemblyMetadata("SourceRevisionId", "someHash")]
// Custome attribute
[assembly: My.Namespace.MyGitHashAttribute("someHash")]
// Timestamp
[assembly: BuildDateAttribute("20230330140538")]
// We could also use the existing one
[assembly: System.Reflection.AssemblyInformationalVersionAttribute("1.0.0+someHash")]
[assembly: System.Reflection.AssemblyCompanyAttribute("MyApp")]
// ...
// Generated by the MSBuild WriteCodeFragment class.

We can then read it from the assembly during runtime.

// define custom attribute if chosen that way
public class MyGitHashAttribute : Attribute 
{
    public string Hash { get; }

    public GitHashAttribute(string hash)
    {
        Hash = hash;
    }
}

// usage at runtime
var hash1 = Assembly.GetEntryAssembly().GetCustomAttributes<AssemblyMetadataAttribute>.FirstOrDefault().Value;
var hash2 = Assembly.GetEntryAssembly().GetCustomAttribute<MyGitHashAttribute>().Hash;
var hash3 = Assembly.GetEntryAssembly().GetCustomAttribute<BuildDateAttribute>().Date;