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xamarin git pull nuget package error

I am new in Xamarin android development.
I take the code pull from git.
After that i opened my solution in visual studio.
I cleaned the solution - now it is fine.
then i trying to build the solution it is showing the error.
>Restoring NuGet packages...
To prevent NuGet from restoring packages during build, open the Visual Studio Options dialog, click on the Package Manager node and uncheck 'Allow NuGet to download missing packages during build.'
NuGet Package restore failed for project app: Unable to find version '2.0.0' of package 'FastAndroidCamera'.
C:\Program Files (x86)\Microsoft SDKs\NuGetPackages\: Package 'FastAndroidCamera.2.0.0' is not found on source 'C:\Program Files (x86)\Microsoft SDKs\NuGetPackages\'.
https://api.nuget.org/v3/index.json: Unable to load the service index for source https://api.nuget.org/v3/index.json.
An error occurred while sending the request.
The remote name could not be resolved: 'api.nuget.org'
1>------ Rebuild All started: Project: app, Configuration: Debug Any CPU ------
1>D:\PRANAV\TOLL\GIT\MobileApp-12-06-2018\MobileApp\app\app.csproj(467,5): error : This project references NuGet package(s) that are missing on this computer. Use NuGet Package Restore to download them. For more information, see http://go.microsoft.com/fwlink/?LinkID=322105. The missing file is ..\packages\Xamarin.Build.Download.0.4.3\build\Xamarin.Build.Download.props.
========== Rebuild All: 0 succeeded, 1 failed, 0 skipped ==========\
This is the error that i am getting . So guys can you figure where i am doing the mistakes ?

According to the error message,
To prevent NuGet from restoring packages during build, open the Visual
Studio Options dialog, click on the Package Manager node and uncheck
'Allow NuGet to download missing packages during build.'
It seems the project use the older now deprecated NuGet package restore that is MSBuild based and runs NuGet.exe on every build. These messages are from NuGet.exe.
Check the similar issue here.
To resolve this issue, you should make sure to upgrade to the latest version of NuGet which does package restore automatically instead of MSBuild based NuGet package restore.
You're going to want to delete the NuGet targets (delete the .nuget folder and then manually edit your .csproj files and remove the lines that import the NuGet.targets file). This is no longer needed. Using the new way to restore nuget package, the NuGet packages will be automatically restored by Visual Studio just before the build.
See this post by David Ebbo for more information: http://blog.davidebbo.com/2014/01/the-right-way-to-restore-nuget-packages.html and the blog how to switch from "Enable Package Restore" to "Automatic Package Restore"
Hope this helps.

NuGet package install fails "Package restore failed. Rolling back package changes for <xamarin.android>"

Installing any package fails with this error, updating packages also creates this error. Clearing the NuGet cache files causes this error to change to "access to the path mono.cecil.dll is denied" when trying to install "Xamarin.GooglePlayServices.Ads". Restarting visual studio causes the package restore error to come back.
Versions:
OS: win 10
Visual Studio Information:https://pastebin.com/vnuyZMWk
Xamarin.Forms Project:
Target framework: .NET 2.0
Xamarin.Android project:
Minimum Android Version: 5.0 (API Level 21)
Target Android Version: Use Compile Using SDK version (8.0)

Well after some trial and error I have the solution.
Visual Studio:
Update visual studio https://pastebin.com/GkEeRqg3
Updates Xamarin.Forms and NuGet
Repair visual studio from the "Visual Studio installer"
This Fixes the access denied to *.dll error
Xamarin.Android project:
Set Target Android Version: 8.1 API 27
This makes the packages the require monoandroid81 happy.
Cleaning house
Delete the folder C:\Users\<Your_Name>\AppData\Local\Xamarin`
Not sure if this was necessary but I am documenting anything I did so others can replicate the solution.
Fixing NuGet
Right-click <Project_name>.android --> Set as startup project.
Tools --> NuGet Package Manager --> Package Manager Console
In the console CLI run Update-Package -Reinstall
Why did this happen?
One way or another some of the NuGet packages used in Xamarin.Android used monoandroid81. Even though my solution was set to use 80 some NuGet packages installed were only compatible with 81. This was shown in the NuGet Console.
Package Xamarin.Android.Support.v7.MediaRouter 27.0.2 is not compatible with monoandroid80 (MonoAndroid,Version=v8.0). Package Xamarin.Android.Support.v7.MediaRouter 27.0.2 supports:
monoandroid81 (MonoAndroid,Version=v8.1)

I faced the same error when I was trying to update the libraries one by one. Then I tried selecting all required libraries and clicked the Update button bellow the search box and it works. I have to tell that these libraries had dependencies between each other.
Here's an example:

Visual Studio - Microsoft.bcl.build.targets, unload project option not available

I'm getting the following error:
This project references NuGet packages(s) that are missing on this computer. Use Nuget Package Restore to download them... This missing file is ..\packages\Microsoft.Bcl.Build.1.0.21\build\Microsoft.Bcl.Build.targets
When I run "Install-Package Microsoft.Bcl.Build -Version 1.0.21" in my Package Manager Console nothing happens.
I've tried to unload the project but, when I right click on the project name I don't see an option for "Unload".
This is the only error I'm seeing when I build the project.

Visual Studio NuGet Cannot Restore Packages

I have a large project that has about a dozen dependencies. I have tried to install them all but ran into an error from VS. I am using Visual Studio 2015
"An error occurred while trying to restore packages: Unable to find version '3.0.3.1' of package'Lucene.Net.Core'."
Now I have a solution which I can use that is by the same name as this package, but VS refuses to let me updates, remove, or change ANYTHING related to these packages and asks that I restore the packages. I am entirely lost here friends, what should I do?
P.S. the two sources I am using for my package sources are:
https://www.nuget.org/api/v2/
https://www.nuget.org/api/v2/curated-feeds/microsoftdotnet/
The same error occurs for Lucene.Net.Contrib, pstsdk.net, and various packages.

One thing to check for is if your project is built on a version of the NET framework that is less than or equal to the target framework the package has.
If your project is a NET 4.5 based project, but the nuget package has a NET 4.5.2... then the package manager will error out.

"An error occurred while trying to restore packages: Unable to find version '3.0.3.1' of package'Lucene.Net.Core'."
When I use the packages sources which you provided, I found that only two versions (4.8.0 & 4.9.0) of package"Lucene.Net.Core" not have the version '3.0.3.1'.
Pay Attention:
I noticed that the author of this package have updated this package at March 11, 2017(3/11/2017), and only release the version 4.8.0 & 4.9.0. So this must be the reason for NuGet restore failed.
Besides, you said:
I have a solution which I can use that is by the same name as this
package, but VS refuses to let me updates, remove, or change ANYTHING
related to these packages
If you want to remove those error packages, you can try to use below command to force uninstall those packages:
Uninstall-Package Lucene.Net.Core -Force
Or you can delete this package from the package folder and delete the package list from the package.config.
Then install the correct version of the packages.

Although I was not able to get any of the posted answers to work, I ended up removing the project entirely and reinstalling VS, my project, and its dependencies. This ended up working.

Another thing to check is that the package manager configuration settings in visual studio list the public nuget feed (and if the feed is enabled too).

Nuget Packages are missing in Visual Studio

I have been using xamarin studio, it works fine when I download a sample project from mvvmcross. It compiles and deploys the device perfectly.
But when I open the project in the visual studio, there are a lot of missing packages for some reasons. Is there a way of handling ? I am using Nuget 2.8 in Visual studio 2013
When I open Nuget as follows, there is a button to restore the missing packages. I clicked on it.
Then it is attempting to download the missing packages, and then it realizes there are dependencies as follows:
Then I am attempting to download the dependency manually as follows but it shows the packages has already downloaded but I am still seeing the missing packages in the solution, nothing is affected.
Therefore I am getting hundreds of errors as follows:
When I take a look at the property of missing packages, I see as follows

You should update your NuGet Package Manager extension in Visual Studio and then try restoring the packages again.
The restore error MvvmCross.Binding already has a dependency defined for MvvmCross.Core is caused by an old version of the NuGet package manager extension not recognising the newer target frameworks that the MvvmCross.Binding NuGet package is using in its group dependencies. This bug has been fixed in a newer version of the NuGet Package Manager.
If you search for the 'already has a dependency defined' error message you will find several cases of this, such as this StackOverflow question, for example:
Can not install NuGet package

Right click on the solution in solution explorer and choose 'restore nuget packages'