Calling Powershell from C# (ASP.NET) - pass custom object?

I'm having trouble trying to call a Powershell function from C#. Specifically, I'm getting stuck trying to pass a generic list of Project's to a powershell module function. Here is the code:

var script = @". \\server01\Modules\Runspace.ps1; Get-MyCommand";
var allProjects = _pmRepository.GetAllProjects();
using (Runspace runSpace = RunspaceFactory.CreateRunspace())
{
    runSpace.Open();
    PowerShell posh = PowerShell.Create();
    posh.Runspace = runSpace;
    posh.AddScript(script);
    posh.AddArgument(allProjects);

    Collection<PSObject> results = posh.Invoke();
}

The GetAllProjects() method returns a generic list of Project's and Project is a custom class. My module function signature looks like this:

function Get-MyCommand
{
    [CmdletBinding()]
    Param
    (
        [Parameter(ValueFromPipeline = $true)]
        [PSCustomObject[]] $Projects
    )
    Begin
    {}
    Process
    {
        $consumables = New-GenericList "Company.Project.Entities.Project"
        foreach($project in $projects)
        {
            if ($project.State -eq $ProjectStates.Development)
            {
                $consumables.Add($project)
            }
        }
    }
}

I'm getting this error when I try to iterate over the array:

{"Property 'State' cannot be found on this object. Make sure that it exists."}

Is it possible to do what I'm trying to do?

Edit: I used the below code for a while, but ended up consuming the back-end C# code for this web application. The load time to create a powershell session was just too great for our situation. Hope this helps.

    private void LoadConsumableProjects()
    {
        var results = new Collection<PSObject>();
        InitialSessionState iss = InitialSessionState.CreateDefault();
        iss.ImportPSModule(_modules);

        using (Runspace runSpace = RunspaceFactory.CreateRunspace(iss))
        {
            runSpace.Open();
            using (var ps = PowerShell.Create())
            {
                ps.Runspace = runSpace;
                ps.AddScript("Get-LatestConsumableProjects $args[0]");
                ps.AddArgument(Repository.GetAllProjects().ToArray());

                results = ps.Invoke();
                if (ps.Streams.Error.Count > 0)
                {
                    var errors = "Errors";
                }
            }
        }

        _projects = new List<Project>();
        foreach (var psObj in results)
        {
            _projects.Add((Project)psObj.BaseObject);
        }
    }