JsonSerializer throws exception in xamarin.ios

Question

While in android everything works fine (as most times), in iOS this line
var payload = System.Text.Json.JsonSerializer.Serialize(postData);
throws an exception:

System.TypeInitializationException: The type initializer for 'System.Text.Json.JsonSerializer' threw an exception. ---> System.MissingMethodException: Method not found: int System.Text.Encodings.Web.TextEncoder.FindFirstCharacterToEncodeUtf8(System.ReadOnlySpan1) at System.Text.Json.JsonEncodedText.EncodeHelper (System.ReadOnlySpan1[T] utf8Value, System.Text.Encodings.Web.JavaScriptEncoder encoder) [0x00000] in <7e3a59f5e4004edbb4b17c580799cc52>:0
at System.Text.Json.JsonEncodedText.TranscodeAndEncode (System.ReadOnlySpan1[T] value, System.Text.Encodings.Web.JavaScriptEncoder encoder) [0x00033] in <7e3a59f5e4004edbb4b17c580799cc52>:0 at System.Text.Json.JsonEncodedText.Encode (System.ReadOnlySpan1[T] value, System.Text.Encodings.Web.JavaScriptEncoder encoder) [0x00014] in <7e3a59f5e4004edbb4b17c580799cc52>:0
at System.Text.Json.JsonEncodedText.Encode (System.String value, System.Text.Encodings.Web.JavaScriptEncoder encoder) [0x00014] in <7e3a59f5e4004edbb4b17c580799cc52>:0
at System.Text.Json.JsonSerializer..cctor () [0x00042] in <7e3a59f5e4004edbb4b17c580799cc52>:0

But it works fine with Newtonsoft:

var payload = Newtonsoft.Json.JsonConvert.SerializeObject(postData);

I have the latest packages of everything.

Is it a known issue in iOS?

Accepted Answer

To solve the crash when serialising JSON when logging in using System.Text.Json.JsonSerializer instead of NewtonSoft.JSON.

=> Method not found: int System.Text.Encodings.Web.TextEncoder.FindFirstCharacterToEncodeUtf8

You have to add this to the iOS App project:

none

none

Answer

We get the same error message when deserialiszing:

var data = JsonSerializer.Deserialize>(json);

The error is reproducible with Visual Studio 2019 for Mac version 8.9 but not with version 8.8.6. This affects only iOS. More specifically it is the Xamarin.iOS version 14.14.2.5 that has the bug. If you downgrade manually to the Xamarin.iOS version 14.8.0.3 everything is fine again. Deserializing works on Android with both versions of Visual Studio.

Version 8.9:

=== Visual Studio Community 2019 for Mac ===

Version 8.9 (build 1651)
Installation UUID: 00f5a6c3-e367-494e-ac05-f885ac415e0c
GTK+ 2.24.23 (Raleigh theme)
Xamarin.Mac 6.18.0.23 (d16-6 / 088c73638)

Package version: 612000122

=== Mono Framework MDK ===

Runtime:
Mono 6.12.0.122 (2020-02/c621c35ffa0) (64-bit)
Package version: 612000122

=== Roslyn (Language Service) ===

3.9.0-5.21112.8+f3ff04378c972d435826e6181de364b3c0db8d14

=== NuGet ===

Version: 5.8.0.6860

=== .NET Core SDK ===

SDK: /usr/local/share/dotnet/sdk/5.0.103/Sdks
SDK Versions:
5.0.103
5.0.102
5.0.101
5.0.100
3.1.406
3.1.405
3.1.404
3.1.403
3.1.402
3.1.401
3.1.302
3.1.301
3.1.300
3.1.200
3.1.102
3.1.101
3.1.100
3.0.101
3.0.100
2.1.701
2.1.700
2.1.505
2.1.504
2.1.503
2.1.302
2.1.301
2.1.4
MSBuild SDKs: /Applications/Visual Studio.app/Contents/Resources/lib/monodevelop/bin/MSBuild/Current/bin/Sdks

=== .NET Core Runtime ===

Runtime: /usr/local/share/dotnet/dotnet
Runtime Versions:
5.0.3
5.0.2
5.0.1
5.0.0
3.1.12
3.1.11
3.1.10
3.1.9
3.1.8
3.1.7
3.1.6
3.1.5
3.1.4
3.1.2
3.1.1
3.1.0
3.0.1
3.0.0
2.1.23
2.1.22
2.1.21
2.1.20
2.1.19
2.1.18
2.1.16
2.1.15
2.1.14
2.1.13
2.1.12
2.1.11
2.1.9
2.1.8
2.1.7
2.1.2
2.1.1
2.0.5

=== .NET Core 3.1 SDK ===

SDK: 3.1.406

=== Xamarin.Profiler ===

Version: 1.6.12.26
Location: /Applications/Xamarin Profiler.app/Contents/MacOS/Xamarin Profiler

=== Updater ===

Version: 11

=== Xamarin Designer ===

Version: 16.9.0.316
Hash: bd2705417
Branch: remotes/origin/d16-9
Build date: 2021-02-24 00:16:08 UTC

=== Xamarin.Android ===

Version: 11.2.0.0 (Visual Studio Community)
Commit: xamarin-android/d16-9/f908d16
Android SDK: /Users/marcoseraphin/Library/Developer/Xamarin/android-sdk-macosx
Supported Android versions:
6.0 (API level 23)
7.1 (API level 25)
8.0 (API level 26)
8.1 (API level 27)

SDK Tools Version: 26.1.1
SDK Platform Tools Version: 31.0.0
SDK Build Tools Version: 29.0.2

Build Information:
Mono: 5e9cb6d
Java.Interop: xamarin/java.interop/d16-9@1d382be
ProGuard: Guardsquare/proguard/v7.0.1@912d149
SQLite: xamarin/sqlite/3.32.2@cfe06e0
Xamarin.Android Tools: xamarin/xamarin-android-tools/main@ad80a42

=== Microsoft OpenJDK for Mobile ===

Java SDK: /Users/marcoseraphin/Library/Developer/Xamarin/jdk/microsoft_dist_openjdk_8.0.25
1.8.0-25
Android Designer EPL code available here:
https://github.com/xamarin/AndroidDesigner.EPL

=== Android SDK Manager ===

Version: 16.9.0.22
Hash: a391de2
Branch: remotes/origin/d16-9
Build date: 2021-02-18 03:14:56 UTC

=== Android Device Manager ===

Version: 16.9.0.17
Hash: fc2b3db
Branch: remotes/origin/d16-9
Build date: 2021-02-18 03:15:18 UTC

=== Apple Developer Tools ===

Xcode 12.4 (17801)
Build 12D4e

=== Xamarin.Mac ===

Version: 7.8.2.5 (Visual Studio Community)
Hash: 3836759d4
Branch: d16-9
Build date: 2021-02-10 17:56:43-0500

=== Xamarin.iOS ===

Version: 14.14.2.5 (Visual Studio Community)
Hash: 3836759d4
Branch: d16-9
Build date: 2021-02-10 17:56:44-0500

=== Build Information ===

Release ID: 809001651
Git revision: c05b1dec4362b5956d47624a437e900ffdc9aa0a
Build date: 2021-02-25 11:27:51-05
Build branch: release-8.9
Xamarin extensions: c05b1dec4362b5956d47624a437e900ffdc9aa0a

=== Operating System ===

Mac OS X 10.15.7
Darwin 19.6.0 Darwin Kernel Version 19.6.0
Thu Oct 29 22:56:45 PDT 2020
root:xnu-6153.141.2.2~1/RELEASE_X86_64 x86_64

=== Enabled user installed extensions ===

LiveXAML 1.3.51
Stack Overflow Search 0.7.1

Version 8.8.6

=== Visual Studio Community 2019 for Mac ===

Version 8.8.6 (build 15)
Installation UUID: 41394e34-af16-4443-a055-e3a05dff10ef
GTK+ 2.24.23 (Raleigh theme)
Xamarin.Mac 6.18.0.23 (d16-6 / 088c73638)

Package version: 612000113

=== Mono Framework MDK ===

Runtime:
Mono 6.12.0.113 (2020-02/4fdfb5b1fd5) (64-bit)
Package version: 612000113

=== Roslyn (Language Service) ===

3.8.0-5.20519.18+4c195c3ac1974edcefa76774d7a59a2350ec55fa

=== NuGet ===

Version: 5.8.0.6860

=== .NET Core SDK ===

SDK: /usr/local/share/dotnet/sdk/5.0.102/Sdks
SDK Versions:
5.0.102
3.1.201
2.1.802
MSBuild SDKs: /Applications/Visual Studio.app/Contents/Resources/lib/monodevelop/bin/MSBuild/Current/bin/Sdks

=== .NET Core Runtime ===

Runtime: /usr/local/share/dotnet/dotnet
Runtime Versions:
5.0.2
3.1.8
3.1.3
2.1.23
2.1.22
2.1.13

=== .NET Core 3.1 SDK ===

SDK: 3.1.201

=== Xamarin.Profiler ===

Version: 1.6.12.29
Location: /Applications/Xamarin Profiler.app/Contents/MacOS/Xamarin Profiler

=== Updater ===

Version: 11

=== Apple Developer Tools ===

Xcode 12.3 (17715)
Build 12C33

=== Xamarin.Mac ===

Version: 7.2.0.3 (Visual Studio Community)
Hash: c51fabee8
Branch: xcode12.3
Build date: 2020-12-10 21:05:04-0500

=== Xamarin.iOS ===

Version: 14.8.0.3 (Visual Studio Community)
Hash: c51fabee8
Branch: xcode12.3
Build date: 2020-12-10 21:05:05-0500

=== Xamarin.Android ===

Version: 11.1.0.26 (Visual Studio Community)
Commit: xamarin-android/d16-8/a36ce73
Android SDK: /Users/Shared/Development/Android/sdk
Supported Android versions:
8.0 (API level 26)
8.1 (API level 27)

SDK Tools Version: 26.1.1
SDK Platform Tools Version: 29.0.4
SDK Build Tools Version: 29.0.2

Build Information:
Mono: 5e9cb6d
Java.Interop: xamarin/java.interop/d16-8@79d9533
ProGuard: Guardsquare/proguard/proguard6.2.2@ebe9000
SQLite: xamarin/sqlite/3.32.1@1a3276b
Xamarin.Android Tools: xamarin/xamarin-android-tools/d16-8@2fb1cbc

=== Microsoft OpenJDK for Mobile ===

Java SDK: /Users/Shared/Development/jdk/microsoft_dist_openjdk_8.0.25
1.8.0-25
Android Designer EPL code available here:
https://github.com/xamarin/AndroidDesigner.EPL

=== Android SDK Manager ===

Version: 16.8.0.32
Hash: 01a7774
Branch: remotes/origin/d16-8
Build date: 2021-01-14 00:34:58 UTC

=== Android Device Manager ===

Version: 16.8.0.46
Hash: 0a81419
Branch: remotes/origin/d16-8
Build date: 2021-01-14 00:35:22 UTC

=== Xamarin Designer ===

Version: 16.8.0.510
Hash: 44e3f3ce9
Branch: remotes/origin/d16-8
Build date: 2020-12-10 00:06:14 UTC

=== Build Information ===

Release ID: 808060015
Git revision: d34d29b4643a130479d762e4d2b5750e6462fde7
Build date: 2021-01-15 08:35:04-05
Build branch: release-8.8
Xamarin extensions: d34d29b4643a130479d762e4d2b5750e6462fde7

=== Operating System ===

Mac OS X 10.15.7
Darwin 19.6.0 Darwin Kernel Version 19.6.0
Mon Aug 31 22:12:52 PDT 2020
root:xnu-6153.141.2~1/RELEASE_X86_64 x86_64

=== Enabled user installed extensions ===

DeepClean 1.2.5

Answer

I have the same issue with Visual Studio for Mac 2019 8.9.1.

System.MissingMethodException: Method not found: int System.Text.Encodings.Web.TextEncoder.FindFirstCharacterToEncodeUtf8(System.ReadOnlySpan1) at System.Text.Json.JsonEncodedText.EncodeHelper (System.ReadOnlySpan1[T] utf8Value, System.Text.Encodings.Web.JavaScriptEncoder encoder) [0x00000] in <815ff95f4d6a463fa6a3be490e0514aa>:0
at System.Text.Json.JsonEncodedText.TranscodeAndEncode (System.ReadOnlySpan1[T] value, System.Text.Encodings.Web.JavaScriptEncoder encoder) [0x00033] in <815ff95f4d6a463fa6a3be490e0514aa>:0 at System.Text.Json.JsonEncodedText.Encode (System.ReadOnlySpan1[T] value, System.Text.Encodings.Web.JavaScriptEncoder encoder) [0x00014] in <815ff95f4d6a463fa6a3be490e0514aa>:0
at System.Text.Json.JsonEncodedText.Encode (System.String value, System.Text.Encodings.Web.JavaScriptEncoder encoder) [0x00014] in <815ff95f4d6a463fa6a3be490e0514aa>:0
at Microsoft.AspNetCore.SignalR.Protocol.JsonHubProtocol..cctor () [0x00000] in :0 } System.MissingMethodException

This happens when I try to initialize an instance of a HubConnectionBuilder from Microsoft.AspNetCore.SignalR.Client. It worked fine with Version 8.8.6 of VS for Mac 2019

Answer

@JessieZhang-MSFT ok so for example I have this payload store in an object IEnumerable:

   [  
     {  
       "Name": "DefaultSearchRange",  
       "Value": 500,  
       "Status": "A",  
       "Id": 1,  
       "CreatedAt": "2021-03-08T22:19:09.2465295"  
     },  
     {  
       "Name": "MaxSearchRange",  
       "Value": 500,  
       "Status": "A",  
       "Id": 2,  
       "CreatedAt": "2021-03-08T22:19:09.2466545"  
     },  
     {  
       "Name": "MaxListingsCount",  
       "Value": 500,  
       "Status": "A",  
       "Id": 3,  
       "CreatedAt": "2021-03-08T22:19:09.246655"  
     },  
     {  
       "Name": "MaxListingPhotosCount",  
       "Value": 3,  
       "Status": "A",  
       "Id": 4,  
       "CreatedAt": "2021-03-08T22:19:09.2466552"  
     },  
     {  
       "Name": "MaxReviewCommentsCount",  
       "Value": 1,  
       "Status": "A",  
       "Id": 5,  
       "CreatedAt": "2021-03-08T22:19:09.2466553"  
     },  
     {  
       "Name": "ListingsPerPage",  
       "Value": 5,  
       "Status": "A",  
       "Id": 6,  
       "CreatedAt": "2021-03-08T22:19:09.2466554"  
     },  
     {  
       "Name": "ListingsPerPage_Home",  
       "Value": 25,  
       "Status": "A",  
       "Id": 7,  
       "CreatedAt": "2021-03-08T22:19:09.2466554"  
     },  
     {  
       "Name": "ReviewsPerPage",  
       "Value": 5,  
       "Status": "A",  
       "Id": 8,  
       "CreatedAt": "2021-03-08T22:19:09.2466556"  
     },  
     {  
       "Name": "ChatMessagesPerPage",  
       "Value": 15,  
       "Status": "A",  
       "Id": 9,  
       "CreatedAt": "2021-03-08T22:19:09.2466557"  
     },  
     {  
       "Name": "RentalsPerPage",  
       "Value": 10,  
       "Status": "A",  
       "Id": 10,  
       "CreatedAt": "2021-03-08T22:19:09.2466558"  
     }  
   ]

SystemSettingDTO looks like this:

   public class SystemSettingDTO : ReactiveObject  
       {  
           public int Id { get; set; }  
     
           public DateTime CreatedAt { get; set; }  
     
           public string Name { get; set; }  
     
           public object Value { get; set; }  
     
           public string Status { get; set; }  
       }

And in Xamarin Forms (in iOS), I try to serialize it like this:

   var json = System.Text.Json.JsonSerializer.Serialize(data);

Answer

Same problem here. Code worked one or two weeks ago (don't work every week in this project). I suspect (not confirmed) that the latest Visual Studio 2019 update to version 8.9.1 caused this since it seems to fit in time. I've now replaced all json serialization and deserialization code with Newtonsoft component (which works) to be able to get a new version out the door.

Method not found: int System.Text.Encodings.Web.TextEncoder.FindFirstCharacterToEncodeUtf8(System.ReadOnlySpan`1)

Stack trace:
at System.Text.Json.JsonEncodedText.EncodeHelper (System.ReadOnlySpan1[T] utf8Value, System.Text.Encodings.Web.JavaScriptEncoder encoder) [0x00000] in <815ff95f4d6a463fa6a3be490e0514aa>:0 at System.Text.Json.JsonEncodedText.Encode (System.ReadOnlySpan1[T] utf8Value, System.Text.Encodings.Web.JavaScriptEncoder encoder) [0x0001a] in <815ff95f4d6a463fa6a3be490e0514aa>:0
at System.Text.Json.JsonPropertyInfo.DeterminePropertyName () [0x000bc] in <815ff95f4d6a463fa6a3be490e0514aa>:0
at System.Text.Json.JsonPropertyInfo.GetPolicies () [0x00006] in <815ff95f4d6a463fa6a3be490e0514aa>:0
at System.Text.Json.JsonPropertyInfoCommon`4[TClass,TDeclaredProperty,TRuntimeProperty,TConverter].Initialize (System.Type parentClassType, System.Type declaredPropertyType, System.Type runtimePropertyType, System.Type implementedPropertyType, System.Reflection.PropertyInfo propertyInfo, System.Type elementType, System.Text.Json.Serialization.JsonConverter converter, System.Text.Json.JsonSerializerOptions options) [0x000a3] in <815ff95f4d6a463fa6a3be490e0514aa>:0
at System.Text.Json.JsonClassInfo.CreateProperty (System.Type declaredPropertyType, System.Type runtimePropertyType, System.Type implementedPropertyType, System.Reflection.PropertyInfo propertyInfo, System.Type parentClassType, System.Text.Json.Serialization.JsonConverter converter, System.Text.Json.JsonSerializerOptions options) [0x00184] in <815ff95f4d6a463fa6a3be490e0514aa>:0
at System.Text.Json.JsonClassInfo.AddProperty (System.Type propertyType, System.Reflection.PropertyInfo propertyInfo, System.Type classType, System.Text.Json.JsonSerializerOptions options) [0x0002f] in <815ff95f4d6a463fa6a3be490e0514aa>:0
at System.Text.Json.JsonClassInfo..ctor (System.Type type, System.Text.Json.JsonSerializerOptions options) [0x000d3] in <815ff95f4d6a463fa6a3be490e0514aa>:0
at System.Text.Json.JsonSerializerOptions.GetOrAddClass (System.Type classType) [0x00017] in <815ff95f4d6a463fa6a3be490e0514aa>:0
at System.Text.Json.ReadStackFrame.Initialize (System.Type type, System.Text.Json.JsonSerializerOptions options) [0x00000] in <815ff95f4d6a463fa6a3be490e0514aa>:0
at System.Text.Json.JsonSerializer.ReadCore (System.Type returnType, System.Text.Json.JsonSerializerOptions options, System.Text.Json.Utf8JsonReader& reader) [0x00008] in <815ff95f4d6a463fa6a3be490e0514aa>:0
at System.Text.Json.JsonSerializer.Deserialize (System.String json, System.Type returnType, System.Text.Json.JsonSerializerOptions options) [0x0009d] in <815ff95f4d6a463fa6a3be490e0514aa>:0
at System.Text.Json.JsonSerializer.Deserialize[TValue] (System.String json, System.Text.Json.JsonSerializerOptions options) [0x00000] in <815ff95f4d6a463fa6a3be490e0514aa>:0

JsonSerializer throws exception in xamarin.ios

8 additional answers