無法從程序集'Xamarin.Forms.Core'加載類型'Xamarin.Forms.Preserve屬性'

我剛剛繼承了舊的Xamarin Forms應用程序，我試圖升級所有程序包。應用程序最初運行良好，但由於升級到所有軟件包的最新版本，我現在得到一個崩潰調用Xamarin.Forms.Forms.Init(this, bundle);：無法從程序集'Xamarin.Forms.Core'加載類型'Xamarin.Forms.Preserve屬性'

Could not load type 'Xamarin.Forms.PreserveAttribute' from assembly 'Xamarin.Forms.Core, Version=2.0.0.0, Culture=neutral, PublicKeyToken=null'.

這是我的packages.config文件內容：

<?xml version="1.0" encoding="utf-8"?> 
<packages> 
    <package id="ExifLib.PCL" version="1.0.1" targetFramework="MonoAndroid50" /> 
    <package id="Microsoft.Bcl" version="1.1.10" targetFramework="MonoAndroid50" /> 
    <package id="Microsoft.Bcl.Build" version="1.0.21" targetFramework="MonoAndroid50" /> 
    <package id="Microsoft.Net.Http" version="2.2.29" targetFramework="MonoAndroid50" /> 
    <package id="Newtonsoft.Json" version="8.0.3" targetFramework="MonoAndroid50" /> 
    <package id="Xamarin.Android.Support.Animated.Vector.Drawable" version="23.3.0" targetFramework="MonoAndroid50" /> 
    <package id="Xamarin.Android.Support.Design" version="23.3.0" targetFramework="MonoAndroid50" /> 
    <package id="Xamarin.Android.Support.v4" version="23.3.0" targetFramework="MonoAndroid50" /> 
    <package id="Xamarin.Android.Support.v7.AppCompat" version="23.3.0" targetFramework="MonoAndroid50" /> 
    <package id="Xamarin.Android.Support.v7.CardView" version="23.3.0" targetFramework="MonoAndroid50" /> 
    <package id="Xamarin.Android.Support.v7.MediaRouter" version="23.3.0" targetFramework="MonoAndroid50" /> 
    <package id="Xamarin.Android.Support.v7.RecyclerView" version="23.3.0" targetFramework="MonoAndroid50" /> 
    <package id="Xamarin.Android.Support.Vector.Drawable" version="23.3.0" targetFramework="MonoAndroid50" /> 
    <package id="Xamarin.Forms" version="2.3.0.38-pre2" targetFramework="MonoAndroid50" /> 
    <package id="Xamarin.Forms.Labs" version="1.2.1-pre2" targetFramework="MonoAndroid44" /> 
    <package id="Xamarin.Forms.Maps" version="2.2.0.31" targetFramework="MonoAndroid50" /> 
    <package id="Xamarin.GooglePlayServices.Base" version="29.0.0.1" targetFramework="MonoAndroid50" /> 
    <package id="Xamarin.GooglePlayServices.Basement" version="29.0.0.1" targetFramework="MonoAndroid50" /> 
    <package id="Xamarin.GooglePlayServices.Maps" version="29.0.0.1" targetFramework="MonoAndroid50" /> 
    <package id="Xamarin.Insights" version="1.12.3" targetFramework="MonoAndroid50" /> 
</packages>

來源

2016-05-16 Mick Byrne

我看到你正在嘗試使用Forms 2.3.0.38-pre2 packkage。確保您還將Forms.Maps包更新爲相應的預先版本！ –