C# .NET Core IoT Error for ARM embedded board : Unhandled exception. System.IO.IOException: Device or resource busy

I want to use .NET core IoT library in order to run C# code for my SAMA5D27 SOM1 EK1 ARM embedded board.

.NET core IoT github

I have build this .NET core project composed from project.cs source file :

using System;
using System.Device.Gpio;
using System.Threading;

namespace led_blink
{
    class Program
    {
        static void Main(string[] args)
        {
            var pin = 81;
            var lightTimeInMilliseconds = 1000;
            var dimTimeInMilliseconds = 200;
            
            Console.WriteLine($"Let's blink an LED!");
            using (GpioController controller = new GpioController())
            {
                controller.OpenPin(pin, PinMode.Output);
                Console.WriteLine($"GPIO pin enabled for use: {pin}");

                Console.CancelKeyPress += (object sender, ConsoleCancelEventArgs eventArgs) =>
                {
                    controller.Dispose();
                };

                while (true)
                {
                    Console.WriteLine($"Light for {lightTimeInMilliseconds}ms");
                    controller.Write(pin, PinValue.High);
                    Thread.Sleep(lightTimeInMilliseconds);
                    Console.WriteLine($"Dim for {dimTimeInMilliseconds}ms");
                    controller.Write(pin, PinValue.Low);
                    Thread.Sleep(dimTimeInMilliseconds);
                }
            }
        }
    }
}

And this is .csproj file :

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

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>netcoreapp3.1</TargetFramework>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Iot.Device.Bindings" Version="1.0.0" />
    <PackageReference Include="System.Device.Gpio" Version="1.0.0" />
  </ItemGroup>

</Project>

As you can see, the code is used for blinking Led which is situated on PIN 81 which corresponds to PortC pin 17 on my board. I build the project in order to use on arm-linux board.

First, to check if the pin is working well, I used libgpiod library and I turned on the led of pin81 using gpioset gpiochip0 81=1 and it is working well.

Furthermore, I have checked my GPIOs using gpioinfo command and this is the result of the desired pin :

 line  81:       "PC17"       unused   input  active-high

But when I try to run the C# code, it fails with this output message :

Let's blink an LED!
Unhandled exception. System.IO.IOException: Device or resource busy
   at System.IO.FileStream.WriteNative(ReadOnlySpan`1 source)
   at System.IO.FileStream.FlushWriteBuffer()
   at System.IO.FileStream.FlushInternalBuffer()
   at System.IO.FileStream.Flush(Boolean flushToDisk)
   at System.IO.FileStream.Flush()
   at System.IO.StreamWriter.Flush(Boolean flushStream, Boolean flushEncoder)
   at System.IO.StreamWriter.Dispose(Boolean disposing)
   at System.IO.TextWriter.Dispose()
   at System.IO.File.WriteAllText(String path, String contents)
   at System.Device.Gpio.Drivers.SysFsDriver.OpenPin(Int32 pinNumber)
   at System.Device.Gpio.GpioController.OpenPin(Int32 pinNumber)
   at System.Device.Gpio.GpioController.OpenPin(Int32 pinNumber, PinMode mode)
   at led_blink.Program.Main(String[] args) in /home/ubuntu/netcore/Program.cs:line 23
Aborted

This is my board device tree :

device_tree

PS : I have removed ISC node which is using PC17 GPIO from device tree in order to free the pin

ISC_DeviceTree_node

Why my code can't run ? any help please !