microsoft/aspire · error · ArgumentNullException

Value cannot be null. (Parameter 'processRunner')

Error message

Value cannot be null. (Parameter 'processRunner')

What it means

The ContainerRuntimeBase protected constructor guards its IProcessRunner dependency with ArgumentNullException. Without a process runner the runtime cannot execute docker/podman commands, so construction is refused.

Solutions

1. Register IProcessRunner in the DI container and resolve it when creating the runtime.
2. In tests, supply a real ProcessRunner or a hand-written stub implementing IProcessRunner.
3. Forward the dependency from the subclass constructor instead of passing null.

Example fix

// before
new DockerRuntime(logger, null!);
// after
services.AddSingleton<IProcessRunner, ProcessRunner>();
new DockerRuntime(logger, services.GetRequiredService<IProcessRunner>());

if (processRunner is null) throw new InvalidOperationException("ContainerRuntimeBase requires a non-null IProcessRunner");

static bool CanCreateRuntime(ILogger<DockerRuntime>? logger, IProcessRunner? runner) => logger is not null && runner is not null;

try { runtime = new DockerRuntime(logger, processRunner); }
catch (ArgumentNullException ex) when (ex.ParamName is "logger" or "processRunner")
{
    processRunner ??= new ProcessRunner(TimeProvider.System, logger!, new DefaultProcessExecutionContextLogger(logger!));
    runtime = new DockerRuntime(logger!, processRunner);
}

When it happens

Trigger: Constructing a concrete ContainerRuntimeBase subclass passing null for the IProcessRunner parameter.

Common situations: IProcessRunner not registered in DI; manual construction in tests passing null; custom subclass hardcoding null instead of forwarding the dependency.

Related errors

• Value cannot be null. (Parameter 'logger')
• A QueueServiceClient could not be configured. Ensure valid…
• An EventProcessorClient could not be configured. Ensure a…
• Application did not register an implementation of
• ArgumentNullException for parameter 'services' (services is…

AI-assisted analysis of microsoft/aspire@25830f84bd (2026-09-16). Data as JSON: /api/errors/2a696b3b26c9e7eb. Report an issue: GitHub.

Appendix: source

Thrown at src/Aspire.Hosting/Publishing/ContainerRuntimeBase.cs:29

using Aspire.Hosting.ApplicationModel;
using Aspire.Hosting.Dcp.Process;
using Microsoft.Extensions.Logging;

namespace Aspire.Hosting.Publishing;

/// <summary>
/// Base class for container runtime implementations that provides common process execution,
/// logging, and error handling patterns.
/// </summary>
internal abstract class ContainerRuntimeBase<TLogger> : IContainerRuntime where TLogger : class
{
    private readonly ILogger<TLogger> _logger;
    private readonly IProcessRunner _processRunner;

    protected ContainerRuntimeBase(ILogger<TLogger> logger, IProcessRunner processRunner)
    {
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
        _processRunner = processRunner ?? throw new ArgumentNullException(nameof(processRunner));
    }

    /// <summary>
    /// Gets the logger instance for use in derived classes.
    /// </summary>
    protected ILogger<TLogger> Logger => _logger;

    /// <summary>
    /// Gets the process runner used for container runtime commands.
    /// </summary>
    protected IProcessRunner ProcessRunner => _processRunner;

    /// <summary>
    /// Gets the name of the container runtime executable (e.g., "docker", "podman").
    /// </summary>
    protected abstract string RuntimeExecutable { get; }

    public abstract string Name { get; }

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