Why ?
When I was trying to update the NuGet Packages for one of my Xamarin projects, I got an error saying “Unable to resolve dependencies.” and the packages wasn’t updated.
The detailed error message is …
Unable to resolve dependencies. ‘Xamarin.Android.Support.Design 25.3.1’ is not compatible with ‘Xamarin.Forms 2.3.4.231 constraint: Xamarin.Android.Support.Design (= 23.3.0)’.

Image 1 : Error
The reason for the error was…
The Android project of my Xamarin solution has been configured to Compile using Android 6.0(Marshmallow) API 23.3.0 . But I was trying to update the Android packages for Android 7.1 (Nougat) API 25.3.1.

Image 2 : Current Android application properties(Compile using Android 6.0)
So the target compilation version is not compatible with the updating version of Android packages.
How To Fix the Error ?
To fix the error we have to change the target framework for compile to “Android 7.1(Nougat)”.
Here are Steps to change the target compile framework..

Image 3 : Right Click on Android Project -> Properties

Image 4 : Current Android application properties(Compile using Android 6.0)

Image 5 : Change Compile Android Version to Android 7.1 (Nougat)
When Change the target compilation version of Android , Visual Studio will ask you to restart the project to configure itself…

Image 6 : “Yes” to close and reopen

Image 7 : App is loading

Image 8 : Again go to NuGet package manager to update Android packages

Image 9 : Select Android Packages v.25.3.1(or the package showing here)

Image 10 : Accept to Agree licence and tearms

Image 11 : You can see changes will be happening (the old packages and new packages). Click OK.

Image 12 : Then the packages will be downloaded and Install Successfully.
Then Re-Build the project and the app will run successfully…
Thanks !
Hi..I am having one of these errors. I installed VS 2017 a couple of days ago. When I go to application properties, under Target Framework, I don’t see – “Android 7.1(Nougat)”.. The list ends at Android 6.0(Marshmallow)?…How to make Android 7.1 appear in the list under Target Framework? ..I have downloaded all the latest SDK’s right up to 25.2.5 from Android SDK manager..? But still nothing..Am I missing a step?
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https://xamarinsharp.com/2017/02/13/java-lang-unsupportedclassversionerror-comandroiddxcommandmain-unsupported-major-minor-version-52-0-how-to-fix-this-error/
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Can you please check your Java Development Kit version ? May be it is 1.7. So you have to upgrade it to JDK 1.8 to get the support for Android 7 or later…
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I have the same problem.
I even have JDK 1.8 already installed on my machine.
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Have you changed the JDK path in visual studio… ?
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And target and compilation platforms. To Install Support Design 25, you should have the selected target frmaework as Android 7-7.1 Nouget.
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Does this mean that my code will only run on 7.0 or above, or am I missing the point?
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If you have select the target framework or compilation framework as nouget (API 25), you should have JdK 1.8.
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Thanks, but I wasn’t clear with my question.
What I mean is this:
If I set “Compile using Android version (Target Framework)” to 7.1,
will my app still be able to run on lower versions such as 5.0 or 6.0?
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Yes. You can select minimum support version too.
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