PROSAGA码农传奇-C#/.net-没有找到处理 Intent Android 的活动

我有一个 xamarin android 应用程序，我想打开一个 pdf 文件。在代码的最后一行之后，我得到了错误
<pre><code>Android.Content.ActivityNotFoundException：没有找到处理意图的活动{ act=android.intent.action.VIEW dat=/storage/emulated/0/docen__.pdf typ=application/pdf flg=0x80000 }

Stream _IS = this.Assets.Open("doc" + GlobalsAndroid.FixedDocumentationLanguageCode + ".pdf");
                                        byte[] _BA = null;
                                        using (BinaryReader _BR = new BinaryReader(_IS))
                                        {
                                            using (MemoryStream ms = new MemoryStream())
                                            {
                                                byte[] _buffer = new byte[4096];
                                                int count;
                                                while ((count = _BR.Read(_buffer, 0, _buffer.Length)) != 0)
                                                    ms.Write(_buffer, 0, count);
                                                _BA = ms.ToArray();
                                            }
                                        }

string _EP = System.IO.Path.Combine(global::Android.OS.Environment.ExternalStorageDirectory.Path, "doc" + GlobalsAndroid.FixedDocumentationLanguageCode + "__.pdf");
                                        System.IO.File.WriteAllBytes(_EP, _BA);

Intent _I = new Intent(Intent.ActionView);
                                        _I.SetDataAndType(global::Android.Net.Uri.Parse(_EP), "application/pdf");
                                        _I.SetFlags(ActivityFlags.GrantReadUriPermission);
                                        _I.SetFlags(ActivityFlags.NewTask);
                                        _I.SetFlags(ActivityFlags.ClearWhenTaskReset);

this.StartActivity(_I);
</code></pre>我的清单是：
<pre><code> <?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" android:versionCode="6" android:versionName="1.3" android:installLocation="auto">
 <uses-sdk android:minSdkVersion="17" android:targetSdkVersion="20" />
 <application android:debuggable="true"></application>
 <uses-permission android:name="android.permission.INTERNET" />
 <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
 <uses-permission android:name="android.permission.READ_INTERNAL_STORAGE" />
 <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
 <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
 <uses-permission android:name="android.intent.action.VIEW" />

</manifest>
</code></pre>我该如何解决？