Can't create SqlParameter in EF Core 3.1.2 in Xamarin.Android application

[sergtk]

I have Android Xamarin.Forms project.
It depends on Db project with EF Core code (SQL Server) and targeted .Net Standard 2.0. Both projects in one solution.

With EF Core 2.2.6 everything works fine.
When I switch to EF Core 3.1.2, the project does not work anymore.

I made the following changes to compile it:

• I added Microsoft.Data.SqlClient 1.1.1 nuget project reference and use namespace Microsoft.Data.SqlClient instead of System.Data.SqlClient
• Replace DbSet<Entitiy>.FromSql calls with DbSet<Entitiy>.FromSqlRaw

When I create SqlParameter and try to access it I get an error.

E.g. when I run the following code:

try
{
    var sqlParam = new SqlParameter("aaa", "bbb");
    var value = sqlParam.Value;
} catch (Exception ex)
{
    Debug.WriteLine($"Message: {ex.Message}");
    Debug.WriteLine($"StackTrace: {ex.StackTrace}");
}

I get the following error messages:

Message: Object reference not set to an instance of an object
StackTrace: at Microsoft.Data.SqlClient.SqlParameter.get_Value () [0x00000] in E:\SqlClientInternal\agent-1_work\5\s\src\Microsoft.Data.SqlClient
etcore\ref\Microsoft.Data.SqlClient.cs:1222
at [0x00012] in .cs:100

When the sqlParam just assigned, and I want to view its value, I get the following view in Visual Studio:

I use Visual Studio 2019, I tried 16.3.4 and the latest as for now 16.4.6.

How to fix this issue? What is wrong with my code?

[cheenamalhotra]

Hi @sergtk

Please take a look at porting-cheat-sheet as there are a few more related namespaces that need update for applicable classes.

[sergtk]

Hi @cheenamalhotra,

Thank you for the link.

When I try to replace namespace System.Data.SqlTypes with Microsoft.Data.SqlTypes I get an error:

error CS0234: The type or namespace name 'SqlTypes' does not exist in the namespace 'Microsoft.Data' (are you missing an assembly reference?)

This is in .NetStandard 2.0 project.
Nuget package Microsoft.Data.SqlClient is added to the project.

Should I add some other packages which are missed?

[cheenamalhotra]

As mentioned in porting sheet, System.Data.SqlTypes namespace changes are applicable to only SqlFileStream.

Since SqlFileStream is only supported in .NET Core and .NET Framework (SqlFileSteam API Reference), you should not change this namespace for any other class in .NET Standard.

[sergtk]

Thank you for clarification.

But it does not help.
In fact I can't execute any SQL query even without parameters.

E.g.

var db = new DataContext1()
var items = db.Items.FromSqlRaw($"SELECT * FROM [dbo].[Items]");
var itemsList = items.ToList();

The third line of code throws System.NullReferenceException exception.

[cheenamalhotra]

Can I see your code if you could upload here in a small repro app?
I want to validate references you have in your project architecture and your code.

[sergtk]

@cheenamalhotra I have uploaded 2 test projects at repo https://github.com/sergtk/AndroidXamarinEFCore

The first project is compiled with EF Core 2.2.6 and works without thrown exceptions: https://github.com/sergtk/AndroidXamarinEFCore/tree/master/AndroidXamarinEFCore226
The only thing is required is to provide correct user name, password, SQL server and database at file https://github.com/sergtk/AndroidXamarinEFCore/blob/master/AndroidXamarinEFCore226/AndroidXamarinEFCore/Db/App/Db/Config.cs

The second project is updated to EF Core 3.1.2 from the project above: https://github.com/sergtk/AndroidXamarinEFCore/tree/master/AndroidXamarinEFCore312
The error described in this ticket is reproduced in it.
It can be compiled and run. The only thing I did before uploading it to github I removed sensitive information in the file https://github.com/sergtk/AndroidXamarinEFCore/blob/master/AndroidXamarinEFCore312/AndroidXamarinEFCore/Db/App/Db/Config.cs

The first exception is thrown at the following line even without correct user name and password:
https://github.com/sergtk/AndroidXamarinEFCore/blob/master/AndroidXamarinEFCore312/AndroidXamarinEFCore/AndroidXamarinEFCore/App1.xaml.cs#L42 (line 42 of the file)

The rest part of the function OnStart() also throws exceptions either when creating SqlParameter instance members after the creation of it, or after executing SQL Statement and accessing selected data. But this part already requires correct access to the database (user name, password, server, database to reproduce the exception thrown.

I didn't provide DB migrations to create a database, but it is quite simple to create the table just with compatible columns with the ones in the C# code.

[cheenamalhotra]

Hi @sergtk

Thanks for the repro, however I'm getting exception "Microsoft.Data.SqlClient is not supported on this platform." when running EFCore312 project with emulator.

Did you manage to get around that issue?

[sergtk]

Hi @cheenamalhotra

I'm getting exception "Microsoft.Data.SqlClient is not supported on this platform."

I didn't get such an error.
But I just rechecked https://www.nuget.org/packages/Microsoft.Data.SqlClient/1.1.1 and I don't see the support of MonoAndroid.
I don't know how the project compiled, I also reinstalled Visual Studio 16.4.6 in case of Visual Studio corrupt.

But since there is no support of MonoAndroid for Microsoft.Data.SqlClient on nuget page, then does this mean that I can't use it on Android?
Does this mean that I should use System.Data.SqlClient to get SQL Server support of EF Core 3.1 on Android?

Anyway the question is how can I use SQL Server with EF Core 3.1 with Android?

Thank you

[cheenamalhotra]

We support .NET Standard 2.0 so any framework that implements that is indirectly supported.

Are you by chance running on Unix platform? As I see the DLL is rightly picked for Unix runtime.

While on Windows, the DLL seems to be picked from 'lib' folder and not 'runtime', which throws NotSupportedException.

Can I debug for Unix to use the right DLL?

[sergtk]

I use Windows 10.
I don't use Unix for development.

Probably these paths are shown somewhere for Android which is Unix like, but I didn't do something concerning Unix manually.

When I go to definition of SqlParameter class in Visual Studio during debugging, I get to the windows opened for the following library:

C:\Users\sergdev\.nuget\packages\microsoft.data.sqlclient\2.0.0-preview1.20021.1\ref\netstandard2.0\Microsoft.Data.SqlClient.dll

[cheenamalhotra]

C:\Users\sergdev.nuget\packages\microsoft.data.sqlclient\2.0.0-preview1.20021.1\ref\netstandard2.0\Microsoft.Data.SqlClient.dll

This is ref for Visual Studio Intellisene.

On runtime different DLLs are loaded. But I still get the same error, which is a different problem since I don't work on Xamarin/Mono everyday, I'm not an expert in that area. I ran the app with VS 2019 Preview (as it has most recent updates) - v16.6.0 and .NET Core SDK 3.1.2.

Could you try to simplify the repro and remove layers that are non-relevant?
That might help us better understand underlying problem.

[sergtk]

In fact, the app I uploaded is Android Xamarin.Forms application created by Visual Studio.
I added only EF Core code to reproduce the issue, it is quite straightforward.
I need some time to simplify the code even more.

As for now, I want to make it clear what I need.
I want to get a working sample application for Android Xamarin.Forms with EF Core 3.0+ support for SQL Server.
And I can't get such a sample application working.

In other words, I can't make a sample working application for Android with EF Core 3.0+ with SQL Server.
I would be glad if you have such an example.

Just one more note.
I have no problems creating the working code I need, but with SQLite instead of SQL Server.
The issue I have looks like related to Microsoft.Data.SqlClient.

[cheenamalhotra]

In other words, I can't make a sample working application for Android with EF Core 3.0+ with SQL Server. I would be glad if you have such an example.

I agree, I'm looking into it too.. for my own learning and satisfaction 😄

1 info I'll need is if you can provide me binlog for your repro, in your environment.. you can generate it by running msbuild /bl from solution folder.

[sergtk]

Hi @cheenamalhotra,

I updated sandboxes, they are much simpler now https://github.com/sergtk/AndroidXamarinEFCore

I can't provide binlog yet, because I have some issues to build solution with msbuild, I need investigate this yet.

I hope that EF Core 3.1 really supports Android.Xamarin as stated at https://docs.microsoft.com/en-us/ef/core/platforms/ .