Just started to test android app development using Visual Studio 2012 & Mono droid.
So far so good, but first thing I noticed is that starting new project it did not create AndroidManifest.xml. I found out that you can generate one from Project proporties.
The result:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android">
<uses-sdk />
<application>
</application>
</manifest>
I also noticed that in autogenerated Activity1.cs there is lines:
[Activity(Label = "Apptest", MainLauncher = true, Icon = "@drawable/icon")]
But the the problem rises when I try to delete that line of code above and integrate it via manifest.xml as follows:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android">
<uses-sdk />
<application android:icon="@drawable/Icon">
<activity class=".Activity1"
android:label="Apptests">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>

How can I correctly describe Activity1.cs in my AndroidManifest.xml?
According to Android documentation, there is no such attribute as
<Activity class="">. It should be<Activity android:name="">.But Mono for Android takes care of almost everything in AndroidManifest.xml using custom attributes, so you don’t have to bother adding anything to it.
So in your case, if you insist, the activity section of your AndroidManifest.xml should be like this:
<activity android:name=".Activity1"android:label="Apptests">