Fix DiagnosticsClient.WriteDump to handle dump paths with spaces on Windows

[Copilot]

Summary

Fixes #5020 - DiagnosticsClient.WriteDump() now correctly handles dump file paths containing spaces on Windows.

Problem

When calling WriteDump() with a path containing spaces on Windows, the operation would fail with the error:

[createdump] The pid argument is no longer supported

This occurred because the runtime's createdump utility on Windows was parsing the unquoted path as multiple command-line arguments. For example, a path like C:\my dumps\dump.dmp would be split into C:\my and dumps\dump.dmp, causing the latter part to be misinterpreted as additional arguments.

This issue is specific to Windows due to how the runtime builds the command line for createdump. Linux and macOS do not have this problem.

Solution

The fix wraps the dump path in quotes before sending it to the runtime on Windows only:

• Paths are now automatically quoted on Windows: C:\my dumps\dump.dmp → "C:\my dumps\dump.dmp"
• Logic prevents double-quoting if the path is already quoted (handles the workaround some users may have implemented)
• Non-Windows platforms (Linux/macOS) are unaffected and paths are passed through unchanged

Changes

Modified the two CreateWriteDumpMessage method overloads in DiagnosticsClient.cs to:

1. Check the platform using RuntimeInformation.IsOSPlatform(OSPlatform.Windows)
2. Quote the dump path before serialization only on Windows
3. Check if the path is already quoted to avoid double-quoting

// Quote the path to handle spaces correctly in createdump on Windows only
// Only add quotes if the path is not already quoted
// This is only needed on Windows where the runtime builds the command line for createdump
string pathToUse = dumpPath;
if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
{
    pathToUse = dumpPath.StartsWith("\"") && dumpPath.EndsWith("\"") ? dumpPath : $"\"{dumpPath}\"";
}

Testing

Manually verified the quoting logic handles:

On Windows:

• ✅ Paths without spaces: C:\dumps\dump.dmp → "C:\dumps\dump.dmp"
• ✅ Paths with spaces: C:\my dumps\dump.dmp → "C:\my dumps\dump.dmp" (fixes the issue)
• ✅ Already quoted paths: "C:\my dumps\dump.dmp" → "C:\my dumps\dump.dmp" (no double-quoting)

On Linux/macOS:

• ✅ All paths are passed through unchanged (no quoting applied)

The fix is minimal, backward compatible, platform-specific, and addresses the reported issue while maintaining compatibility with the workaround mentioned in the issue.

[!WARNING]

Fixes #5020

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Diagnostics client fails to create dump when path has spaces</issue_title>
<issue_description>### Description

.NET diagnostics client fails when path to dump file has spaces in it. This reproduces both on net8 and net9, and fails with error:

[createdump] The pid argument is no longer supported coming from here

It can be fixed by wrapping the path to extra "".

I am using the latest version of the client package.

Reproduction Steps

<!-- file DumpError.csproj -->
<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net8.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.Diagnostics.NETCore.Client" Version="0.2.547301" />
  </ItemGroup>

</Project>

// file Program.cs
using Microsoft.Diagnostics.NETCore.Client;
using System.Diagnostics;

public static class Program
{
    public static int Main(string[] args)
    {
        if (args.Length > 0 && args[0] == "--hang")
        {
            Thread.Sleep(int.MaxValue);
        }

        var path = Path.Combine(AppContext.BaseDirectory, "DumpError.exe");
        Process? process = null;
        try
        {
            process = Process.Start(path, "--hang");
            var diagnosticClient = new DiagnosticsClient(process.Id);
            Thread.Sleep(1_000);
            diagnosticClient.WriteDump(DumpType.Full, $"{Path.Combine(AppContext.BaseDirectory, $"my dump with spaces {Stopwatch.GetTimestamp()}.dmp")}", logDumpGeneration: true);
        }
        finally
        {
            process?.Kill();
        }

        return 0;
    }
}

Expected behavior

Spaces are correctly escaped and my dump is written to disk.

Actual behavior

[createdump] The pid argument is no longer supported error is shown and dump is not written.

Regression?

No.

Known Workarounds

Add quotes around the path, or move to folder without spaces.

Configuration

Win 11, 8.0.110, but reproduces on latest net9 as well.

Other information

No response</issue_description>

<agent_instructions>See what you can do to support spaces in the path when generating a dump file calling WriteDump.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

Fixes #5020

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

[steveisok]

@copilot from the comments on the issue this PR is linked to, the quote behavior was only needed on windows. The non-windows targets did not have this problem.

[Copilot]

@copilot from the comments on the issue this PR is linked to, the quote behavior was only needed on windows. The non-windows targets did not have this problem.

Updated the fix to apply quoting only on Windows. The path quoting is now wrapped in a RuntimeInformation.IsOSPlatform(OSPlatform.Windows) check, so Linux/macOS are unaffected. Commit: Updated in the latest commit above.