NSThreadExtensions.cs

using System;
using System.Runtime.InteropServices;
using ObjCRuntime;

static class NSThreadExtensions {
    [DllImport("/usr/lib/libobjc.dylib")]
    static extern void objc_msgSend (IntPtr receiver, IntPtr selector, double thread);
    
    [DllImport("/usr/lib/libobjc.dylib")]
    static extern double double_objc_msgSend (IntPtr receiver, IntPtr selector);> 
    
    public static void SetPriority (this NSThread thread, double priority)
    {
        objc_msgSend (thread.Handle, Selector.GetHandle ("setThreadPriority:"), priority);
    }
    
    public static double GetPriority (this NSThread thread)
    {
        return double_objc_msgSend (thread.Handle, Selector.GetHandle ("threadPriority"));
    }
}