Process API Net11

Process API Improvements — .NET 11

New APIs added to System.Diagnostics.Process in .NET 11 simplify process management, eliminate boilerplate, and prevent common deadlock patterns when capturing output in .NET 11 or later applications.

When to Use

• Running or orchestrating external processes in a .NET 11 (or later) project.

• Needing to start a process, wait for it to exit, and capture its output/error streams without risking deadlocks (Process.RunAndCaptureText[Async]).

• Wanting to ensure child processes are automatically terminated when the parent process exits (KillOnParentExit).

• Requiring lightweight, low-overhead process creation via SafeProcessHandle on supported platforms.

• Requiring fine-grained control over handle inheritance (InheritedHandles) or starting detached processes (StartDetached).

When Not to Use

• The project targets .NET 10 or earlier — these APIs are not available before .NET 11.

• The default Process.Start() is sufficient and does not require output capturing or advanced lifecycle rules.

Target Framework

<TargetFramework>net11.0</TargetFramework>

New APIs

Types

Before using the new convenience methods, note the following types. Use the framework types directly:

ProcessExitStatus describes the outcome of a completed process. Interpret ExitCode using the external command's contract; there is no universal Success property. ProcessTextOutput contains the exit status, captured output and error text, and process ID. ProcessOutputLine identifies one output line and whether it came from standard error.

High-Level Convenience APIs

Static Methods

The ProcessStartInfo overloads below require UseShellExecute = false, which is the default for .NET.

Process.Run / Process.RunAsync

Starts a process and waits for it to exit, returning the exit status. Does not capture standard output or error. Passing silent: true discards standard output and error by internally redirecting standard handles to the NUL device. On timeout or cancellation, the process is killed.

public static ProcessExitStatus Run(string fileName, IEnumerable<string>? arguments = null, bool silent = false, TimeSpan? timeout = null)
public static Task<ProcessExitStatus> RunAsync(string fileName, IEnumerable<string>? arguments = null, bool silent = false, CancellationToken cancellationToken = default)
public static ProcessExitStatus Run(ProcessStartInfo startInfo, TimeSpan? timeout = null)
public static Task<ProcessExitStatus> RunAsync(ProcessStartInfo startInfo, CancellationToken cancellationToken = default)

Process.RunAndCaptureText / Process.RunAndCaptureTextAsync

Starts a process, captures both standard output and error, and waits for it to exit. Extremely useful for avoiding deadlocks on stream redirection. On timeout or cancellation, the process is killed.

When using the ProcessStartInfo overloads, the caller is responsible for setting RedirectStandardOutput = true and RedirectStandardError = true on ProcessStartInfo (because BCL APIs cannot modify the input arguments they were given).

public static ProcessTextOutput RunAndCaptureText(string fileName, IEnumerable<string>? arguments = null, TimeSpan? timeout = null)
public static Task<ProcessTextOutput> RunAndCaptureTextAsync(string fileName, IEnumerable<string>? arguments = null, CancellationToken cancellationToken = default)
public static ProcessTextOutput RunAndCaptureText(ProcessStartInfo startInfo, TimeSpan? timeout = null)
public static Task<ProcessTextOutput> RunAndCaptureTextAsync(ProcessStartInfo startInfo, CancellationToken cancellationToken = default)

Process.StartAndForget

There is a common misconception that when a process is disposed, it's also being killed. This is not the case, as Process.Dispose only releases the resources associated with the process, but does not kill it.

To make it easier to start a process without the need to worry about disposing it, Process.StartAndForget was introduced. The method starts an executable, returns its ID, and immediately releases all handle resources associated with it. Standard handles not supplied through StandardInputHandle, StandardOutputHandle, or StandardErrorHandle go to the null device by default.

StartAndForget throws InvalidOperationException if UseShellExecute or any RedirectStandardInput, RedirectStandardOutput, or RedirectStandardError flag is true. Use a capture or streaming API if output needs to be read.

public static int StartAndForget(string fileName, IEnumerable<string>? arguments = null)
public static int StartAndForget(ProcessStartInfo startInfo)

Instance Methods

These methods are called on a Process instance to directly read stdout and stderr, guaranteeing no OS pipe buffer overflow deadlocks.

Note: Calling these methods requires RedirectStandardOutput = true and RedirectStandardError = true on the ProcessStartInfo passed to Process.Start.

public (string StandardOutput, string StandardError) ReadAllText(TimeSpan? timeout = null)
public Task<(string StandardOutput, string StandardError)> ReadAllTextAsync(CancellationToken cancellationToken = default)
public (byte[] StandardOutput, byte[] StandardError) ReadAllBytes(TimeSpan? timeout = null)
public Task<(byte[] StandardOutput, byte[] StandardError)> ReadAllBytesAsync(CancellationToken cancellationToken = default)
public IEnumerable<ProcessOutputLine> ReadAllLines(TimeSpan? timeout = null)
public IAsyncEnumerable<ProcessOutputLine> ReadAllLinesAsync(CancellationToken cancellationToken = default)

Example of deconstructing the tuple return:

var (stdout, stderr) = await process.ReadAllTextAsync();

ProcessStartInfo Properties

KillOnParentExit

Ensures that the spawned child process is terminated when the current (parent) process exits (including fatal crash and being force killed). Works across Windows, Linux, and Android.

public bool KillOnParentExit { get; set; }

In cross-platform code, guard the property assignment with a supported-platform check, not only the assigned value. If automatic teardown is required, fail explicitly on an unsupported platform instead of starting an unprotected child process. KillOnParentExit requires UseShellExecute = false.

InheritedHandles

Provides precise control over which handles (file descriptors) are inherited by the child process, preventing accidental resource leaks.

• Standard handles (stdin, stdout, stderr) are always included (no need to add them to the list).

• Setting the list to an empty list means only standard handles get inherited.

• Only SafeFileHandle and SafePipeHandle instances are allowed as of today.

• No global lock is used when spawning new processes on Windows (important for tuning projects that spawn multiple processes in parallel).

• Concurrent process starts must not pass the same handle in InheritedHandles: the runtime temporarily changes its inheritance flags. Serialize starts that share a handle, or use separate handles for each concurrent start.

• Do not enable inheritance on the handles before passing them; other process-start APIs could then inherit them unintentionally.

• On Unix systems without native handle-inheritance control, setting this property can severely reduce process-start performance.

• A non-null list requires UseShellExecute = false and cannot be combined with a non-empty UserName.

public IList<SafeHandle>? InheritedHandles { get; set; }

StartDetached

Starts the process detached from the parent's terminal or job session, ensuring it survives the parent's exit.

public bool StartDetached { get; set; }

StartDetached requires UseShellExecute = false.

Examples

1. One-Line Run and Capture Output

Run a process and safely read all output text without stream deadlock risks. For simple CLI operations that don't need cancellation or async scalability, prefer the synchronous overload:

using System;
using System.Diagnostics;

// Run 'git status' and capture output
ProcessTextOutput result = Process.RunAndCaptureText("git", ["status"]);

if (result.ExitStatus.ExitCode == 0)
{
    Console.WriteLine($"Git Output: {result.StandardOutput}");
}
else
{
    Console.WriteLine($"Failed with exit code: {result.ExitStatus.ExitCode}");
    Console.WriteLine($"Error: {result.StandardError}");
}

2. Auto-Killing Child Processes on Parent Exit

On Windows, Linux, and Android, ensure a long-running background worker process is killed when the main application terminates. On other platforms, this example stops before starting the child process:

using System;
using System.Diagnostics;

ProcessStartInfo startInfo = new("dotnet", ["run", "--project", "BackgroundWorker.csproj"]);

if (OperatingSystem.IsWindows() || OperatingSystem.IsLinux() || OperatingSystem.IsAndroid())
{
    startInfo.KillOnParentExit = true;
}
else
{
    throw new PlatformNotSupportedException("This example requires Windows, Linux, or Android.");
}

using Process process = Process.Start(startInfo)!;
// The background worker is now tied to this process's lifecycle

3. Read All Lines From Output

Start a process and read its output lines safely:

using System;
using System.Diagnostics;
using System.Threading.Tasks;

ProcessStartInfo startInfo = new("ping", ["127.0.0.1"])
{
    RedirectStandardOutput = true,
    RedirectStandardError = true
};

using Process process = Process.Start(startInfo)!;
// Read all output lines safely and asynchronously
await foreach (ProcessOutputLine line in process.ReadAllLinesAsync())
{
    string prefix = line.StandardError ? "[Err]" : "[Out]";
    Console.WriteLine($"{prefix} > {line.Content}");
}

4. Read Entire Output Deadlock-Free (Tuple Return)

Start a process with custom ProcessStartInfo and read both stdout and stderr into a deconstructed tuple without buffer deadlocks:

using System;
using System.Diagnostics;
using System.Threading.Tasks;

ProcessStartInfo startInfo = new("git", ["diff"])
{
    RedirectStandardOutput = true,
    RedirectStandardError = true
};

using Process process = Process.Start(startInfo)!;
var (stdout, stderr) = await process.ReadAllTextAsync();

Console.WriteLine($"Diff output: {stdout}");

5. Start and Forget (Fire & Forget)

Launch a helper executable without holding onto system handle structures:

using System;
using System.Diagnostics;

// Fire and forget, getting back only the process ID
int pid = Process.StartAndForget("notepad.exe");
Console.WriteLine($"Notepad started with PID: {pid}");