Sorry for any inconvenience this problem may have caused you.

When building production in both iOS and Android, Xamarin method of deployment for iOS and Android to reduce size of the apps is the recommended way to optimized your application. However, when the linker is enabled, it may cause unexpected errors when the app tries methods which may not be directly referenced by the application, such as LINQ expressions.

The error, Unable to perform data operation due to an error: Sequence contains no matching element, happen because the LINQ is ignored. We need to tell the Android linker to include the System.Xml.Linq assembly (do not exclude that assembly).

Here's how to enable the LINQ expressions in the production build:

Visual Studio

1. Right-click your Android project and choose Properties.
   
   
2. Navigate to the Android Options and select the Linker tab.
   
   
3. Change the Linking to Sdk Assemblies Only then type this inside the Skip linking assemblies: System.Core;mscorlib.
   

Xamarin Studio

1. Double-click your Android project to open the Project Options window.
2. Navigate to the Android Build and select the Linker tab.
   
   
3. Change the Linker behavior to Link SDK assemblies only then type this inside the Ignore assemblies: System.Core;mscorlib.
   

The changes have been applied to SimpleExpense sample.

This should helps.

Hello Yudi,

I just did a quick test on one device, but it seems your solution solved the problem.

Thank you for your quick support.

Thomas

I just did a quick test on one device, but it seems your solution solved the problem.

Glad to know that my post helps.

Should you need further assistance or run into any problems regarding our products, feel free to post it into our forum. We would be happy to assist you again.

Hello Yudi,

just a final question about this topic.

Would you recommend to do this (Ignore System.Core and mscorlib) in every project?

Almost every project uses LINQ and if I understand it right the only drawback of this, is the final size of the app package.

Are there other assemblies you would recommend to exclude from linker optimizations?

Thanks,

Thomas

...

Would you recommend to do this (Ignore System.Core and mscorlib) in every project?

Almost every project uses LINQ ...

Yes, if that's the case, almost every project uses LINQ. You may ignore System.Core and mscorlib in every project.

... and if I understand it right the only drawback of this, is the final size of the app package.

I unarchived an apk (created using Crosslight with link skip to System.Core and mscorlib) to a directory and looked to the files in Windows Explorer. Here is the uncompressed size mscorlib and all System.xxx.dll:

• mscorlib.dll (1.91 MB)
• all System.xxx.dll (2.67 MB)

If you are concern to optimize the size of the compiled apk, you might want to try use linking: SDK Assemblies (or even All Assemblies), and go through the process of marking classes with the Android preserve attribute, [Android.Runtime.Preserve].

You can also create separate packages, one with armeabi only (for very old devices), one with armeabiv7a, and one with x86. Google play supports having 3 separate packages with different capabilities (don"t forget to change the capabilities in your manifest file for each package).

Next, you can use ProGuard, an Android SDK tool used to create smaller applications by reducing the footprint of large included libraries (such as Google Play Services) in your APK. It removes unused Java bytecode, which makes the resulting app smaller.

Are there other assemblies you would recommend to exclude from linker optimizations?

As far as I know, no other assemblies but System.Core and mscorlib.

Hope this helps.