<Project Sdk="Microsoft.NET.Sdk">

    <PropertyGroup>
        <OutputType>Exe</OutputType>
        <TargetFramework>net481</TargetFramework>
        <ImplicitUsings>enable</ImplicitUsings>
        <Nullable>enable</Nullable>
        <LangVersion>12</LangVersion>
    </PropertyGroup>

    <!-- CsWhispers package -->
    <ItemGroup>
      <PackageReference Include="CsWhispers" Version="0.0.3" />
    </ItemGroup>

    <!-- Allow unsafe code -->
    <PropertyGroup Condition=" '$(Configuration)' == 'Debug' ">
      <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
    </PropertyGroup>

    <PropertyGroup Condition=" '$(Configuration)' == 'Release' ">
      <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
    </PropertyGroup>

</Project>

<ItemGroup>
  <None Remove="CsWhispers.txt" />
  <AdditionalFiles Include="CsWhispers.txt" />
</ItemGroup>

NtOpenProcess

HANDLE
NTSTATUS
CLIENT_ID
UNICODE_STRING
OBJECT_ATTRIBUTES

PWSTR
PCWSTR

public static unsafe void Main()
{
    // use self as example
    using var self = Process.GetCurrentProcess();
        
    HANDLE hProcess;
    OBJECT_ATTRIBUTES oa;
    CLIENT_ID cid = new()
    {
        UniqueProcess = new HANDLE((IntPtr)self.Id)
    };

    var status = NtOpenProcess(
        &hProcess,
        PROCESS_ALL_ACCESS,
        &oa,
        &cid);

    Console.WriteLine("Status: {0}", status.SeverityCode);
    Console.WriteLine("HANDLE: 0x{0:X}", hProcess.Value.ToInt64());
}

namespace CsWhispers;

public static partial class Syscalls
{
    public static NTSTATUS NtCreateThreadEx()
    {
        // whatever
        return new NTSTATUS(0);
    }
}

namespace ConsoleApp1;

internal static class Program
{
    public static void Main()
    {
        var status = NtCreateThreadEx();
    }
}