c# 枚举安卓系统中所有目录及文件名

using Android.App;
using Android.Widget;
using Android.OS;
using System.Runtime.InteropServices;

namespace App2
{
    [Activity(Label = "App2", MainLauncher = true, Icon = "@drawable/icon")]
    public class MainActivity : Activity
    {
        [DllImport("TestDynamicSharedLib.so")]
        public extern static int getClickCount();

        protected override void OnCreate(Bundle bundle)
        {
            var c = getClickCount();

            string folderPath = Android.OS.Environment.ExternalStorageDirectory.AbsolutePath;

            printAllSubFiles(folderPath);

            base.OnCreate(bundle);

            // Set our view from the "main" layout resource
            // SetContentView (Resource.Layout.Main);
        }

        void printAllSubFiles(string path)
        {
            System.Diagnostics.Debug.Print("dir:" + path);

            var dir = new System.IO.DirectoryInfo(path);

            try
            {
                foreach (var f in dir.GetFiles())
                {
                    System.Diagnostics.Debug.Print("file:" + f.FullName);
                }
            }
            catch 
            {
                //throw;
            }

            try
            {
                foreach (var d in dir.GetDirectories())
                {
                    printAllSubFiles(d.FullName);
                }
            }
            catch (System.Exception)
            {
                //throw;
            }
            
        }
    }
}

 如果是android 6.0 以上系统，须代码主动申请权限，此时需要Android.Support.v4。

nuget command : Install-Package Xamarin.Android.Support.v4 -Version 28.0.0.1

void checkPermission(string permissionName)
        {
            if (Android.Support.V4.App.ActivityCompat.CheckSelfPermission(this, permissionName)
                != (int)Android.Content.PM.Permission.Granted)
            {
                //用户已经拒绝过一次，再次弹出权限申请对话框需要给用户一个解释
                if (Android.Support.V4.App.ActivityCompat.ShouldShowRequestPermissionRationale(this, permissionName))
                    Toast.MakeText(this, "请开通相关权限，否则无法正常使用本应用！", ToastLength.Short).Show();

                //申请权限
                Android.Support.V4.App.ActivityCompat.RequestPermissions(this, new String[] { permissionName }, 0);
                Toast.MakeText(this, "请开通相关权限，否则可能无法正常使用本应用！", ToastLength.Short);
            }
            else
            {
                Toast.MakeText(this, "授权成功！", ToastLength.Short);
            }
        }

调用：

checkPermission(Android.Manifest.Permission.ReadExternalStorage);
checkPermission(Android.Manifest.Permission.WriteExternalStorage);