Xamarin.Android SD卡的读写System.UnauthorizedAccessException

[qq_32726357]

//参数
//context
///test.zip
///storage/emulated/0/
public static void CopyToSD(Context ctx, string fileName,string outPath)
		{
			
            outPath = outPath + "/" + fileName;
            Java.IO.File ttf = new Java.IO.File(outPath);//ROOT_FONT_SRC
            if (!ttf.ParentFile.Exists())
			{
                ttf.ParentFile.Mkdirs();
			}

			try
			{
                //ttf.CreateNewFile();
                using (System.IO.Stream fsRead = ctx.Assets.Open(fileName))
                {
                    byte[] buffer = new byte[1024];
                    int length;

                    while ((length = fsRead.Read(buffer, 0, buffer.Length)) > 0)
                    {
              报错语句：          System.IO.FileStream dbOut = new System.IO.FileStream(outPath, System.IO.FileMode.Append);//ROOT_FONT_SRC
                        dbOut.Write(buffer, 0, buffer.Length);
                    }


					
                    UnZip(outPath, "/data/user/0/cn.x189.sh.caimomo/files/", null);
                }
																			
				          
			}
			catch (Exception e1)
			{
				//e.printStackTrace();
			}
		}

报错语句处提示：System.UnauthorizedAccessException: Access to the path "/storage/emulated/0/test.zip" is denied.

查了下说是权限问题，然后配置了manifest.xml里如下：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" android:versionCode="1" android:versionName="1.0" package="cn.x189.sh.caimomo" android:installLocation="auto">
<uses-sdk android:minSdkVersion="23" />
<application android:label="CaiMoMo"></application>
<uses-permission android:name="android.permission.INTERNET" />
<!-- SDCard中创建与删除文件权限 -->
<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" />
<!-- 向SDCard写入数据权限 -->
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
</manifest>

可问题还是存在，求大牛帮帮忙，本人自学Xamarin中，全程百度，一脸蒙币，谁有教程跪求分享，谢谢各位大牛们！！

[qq_32726357]

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