MSBuild BuildInParallel, custom task spawning process that fails to run

I'm using the BuildInParallel attribute of the MSBuild task to run build projects in parallel. The root project is building four child projects. The child projects are using a custom MSBuild task which starts a new process using System.Diagnostics.Process. For some reason the spawned process fails to run properly when UseShellExecute is false. I've no idea why this is and I can't figure out what the error is - all that happens is the Process.ExitCode is 1, no exception..

Here's the custom MSBuild task:

using System;
using Microsoft.Build.Utilities;
using System.Diagnostics;

public class MSBuildProcessTask : Task
{
    public string Executable { get; set; }
    public string Arguments { get; set; }

    public override bool Execute()
    {
        using (var p = new Process())
        {
            try
            {
                p.StartInfo = new ProcessStartInfo(Executable, Arguments)
                                {
                                    UseShellExecute = false,
                                    //RedirectStandardOutput = true
                                };
                //p.OutputDataReceived += (o, e) =>
                //{
                //    if (e.Data != null)
                //    {
                //        Log.LogMessage(MessageImportance.Normal, e.Data);
                //    }
                //};
                p.Start();
                //p.BeginOutputReadLine();
                p.WaitForExit();
            }
            catch (Exception e)
            {
                throw; // for setting breakpoint
            }
            finally
            {
                if (p.ExitCode != 0)
                {
                    Log.LogError("Error.  Exit code: " + p.ExitCode);
                }
                p.Close();
            }
        }
        return true;
    }
}

And here's the root MSBuild project file (Test.proj, actually I'm only building two child project here but still get the error..):

<?xml version="1.0" encoding="utf-8" ?>
<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
    <UsingTask TaskName="MSBuildProcessTask" AssemblyFile="C:\Users\Tom\Sandbox\repository_trunk\MSBuildProcessTask\MSBuildProcessTask\bin\Debug\MSBuildProcessTask.dll" />
    <Target Name="Default">
        <ItemGroup>
            <ProjectFiles Include="$(MSBuildProjectDirectory)\Test.1.proj" />
            <ProjectFiles Include="$(MSBuildProjectDirectory)\Test.2.proj" />
            <!--<ProjectFiles Include="$(MSBuildProjectDirectory)\Test.3.proj" />
            <ProjectFiles Include="$(MSBuildProjectDirectory)\Test.4.proj" />-->
        </ItemGroup>
            <MSBuild BuildInParallel="true" Projects="@(ProjectFiles)" />
    </Target>
</Project>

And here's an example of the child project files (Test.1.proj):

<?xml version="1.0" encoding="utf-8" ?>
<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
    <UsingTask TaskName="MSBuildProcessTask" AssemblyFile="C:\Users\Tom\Sandbox\repository_trunk\MSBuildProcessTask\MSBuildProcessTask\bin\Debug\MSBuildProcessTask.dll" />
    <Target Name="Default">
        <Message Text="Hello" />
        <MSBuildProcessTask Executable="sqlcmd" Arguments="-S .\SQLEXPRESS -Q &quot;SELECT @@VERSION&quot;" />
    </Target>
</Project>

My command line is: C:\Windows\Microsoft.NET\Framework\v4.0.30319\MSBuild.exe /m /nr:false C:\Users\Tom\Sandbox\repository_trunk\MSBuildProcessTask\MSBuildProcessTask\Test.proj

And here's a sample output:

C:\Users\Tom>C:\Windows\Microsoft.NET\Framework\v4.0.30319\MSBuild.exe /m /nr:false C:\Users\Tom\Sandbox\repository_trunk\MSBuildProcessTask\MSBuildPr
ocessTask\Test.proj
Microsoft (R) Build Engine Version 4.0.30319.1
[Microsoft .NET Framework, Version 4.0.30319.235]
Copyright (C) Microsoft Corporation 2007. All rights reserved.

Build started 16/08/2011 22:22:06.
     1>Project "C:\Users\Tom\Sandbox\repository_trunk\MSBuildProcessTask\MSBuildProcessTask\Test.proj" on node 1 (default targets).
     1>Project "C:\Users\Tom\Sandbox\repository_trunk\MSBuildProcessTask\MSBuildProcessTask\Test.proj" (1) is building "C:\Users\Tom\Sandbox\reposito
       ry_trunk\MSBuildProcessTask\MSBuildProcessTask\Test.1.proj" (2) on node 1 (default targets).
     2>Default:
         Hello
     1>Project "C:\Users\Tom\Sandbox\repository_trunk\MSBuildProcessTask\MSBuildProcessTask\Test.proj" (1) is building "C:\Users\Tom\Sandbox\reposito
       ry_trunk\MSBuildProcessTask\MSBuildProcessTask\Test.2.proj" (3) on node 2 (default targets).



------------------------------------------------------------------------------------------------------------------------------------------------------
------------------------------------------------------------------------------------------------------------------------------------------------------

Microsoft SQL Server 2008 (SP1) - 10.0.2531.0 (X64)
        Mar 29 2009 10:11:52
        Copyright (c) 1988-2008 Microsoft Corporation
        Express Edition (64-bit) on Windows NT 6.1 <X64> (Build 7601: Service Pack 1)


(1 rows affected)
     3>Default:
开发者_Python百科         Hello
     2>Done Building Project "C:\Users\Tom\Sandbox\repository_trunk\MSBuildProcessTask\MSBuildProcessTask\Test.1.proj" (default targets).
     3>C:\Users\Tom\Sandbox\repository_trunk\MSBuildProcessTask\MSBuildProcessTask\Test.2.proj(6,3): error : Error.  Exit code: 1
     3>Done Building Project "C:\Users\Tom\Sandbox\repository_trunk\MSBuildProcessTask\MSBuildProcessTask\Test.2.proj" (default targets).
     1>Done Building Project "C:\Users\Tom\Sandbox\repository_trunk\MSBuildProcessTask\MSBuildProcessTask\Test.proj" (default targets).

Build succeeded.

       "C:\Users\Tom\Sandbox\repository_trunk\MSBuildProcessTask\MSBuildProcessTask\Test.proj" (default target) (1) ->
       "C:\Users\Tom\Sandbox\repository_trunk\MSBuildProcessTask\MSBuildProcessTask\Test.2.proj" (default target) (3) ->
       (Default target) ->
         C:\Users\Tom\Sandbox\repository_trunk\MSBuildProcessTask\MSBuildProcessTask\Test.2.proj(6,3): error : Error.  Exit code: 1

    0 Warning(s)
    1 Error(s)

Time Elapsed 00:00:00.23

C:\Users\Tom>

As you can see we only get output from one of the SQLCMD commands.

No chance to say what exactly causes a problem, you have to investigate it yourself or at least provide more details regarding an error.

Try out to run MSBuild specifying diagnostic verbosity level, it will dump very detailed output whilst run:

MsBuild.exe /v:diag

Did you try giving each target a unique name (not 'Default')?

I think that when you include a project, msbuild expands the included project's targets into the current project. When you add another target with the same name as an existing one, the existing one is overridden.

You can see what your expanded project looks like using the /preprocess switch as described here.