NullReferenceException inside .NET code of SqlConnection.CacheConnectionStringProperties()

Question

I'm facing really strange issue. Given the code below:

static void Main()
{
    var c = new System.Data.SqlClient.SqlConnection();

    c.ConnectionString = "Data Source=SOME_NAME;Initial Catalog=SOME_DB;Integrated Security=True";
    c.ConnectionString = ""; //null also triggers exception

    Console.WriteLine("Success");
}

It worked fine for quite a time, but on newest version of Windows 10 (1803) which has .NET Version 4.7.03056 Release 461808 (seems to be 4.7.2) it crashes with following exception:

Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object.
   at System.Data.SqlClient.SqlConnection.CacheConnectionStringProperties()
   at System.Data.SqlClient.SqlConnection.set_ConnectionString(String value)
   at TestCacheConnectionStringProperties.Program.Main()

This crashes on the second assignment, if I remove any of the assignments of the ConnectionString it works ok.

I've looked at the sources and didn't find a place where NullReferenceException could happen (however sources seems to be for .NET Framework 4.7.1 so smth may change).

Now the question is - what causes this issue? Is this a .NET bug? If yes - how to address it?

UPDATE: According to the comments - thanks very much guys - the issue is caused by these lines (decompiled):

private void CacheConnectionStringProperties()
{
  SqlConnectionString connectionOptions = this.ConnectionOptions as SqlConnectionString;
  if (connectionOptions != null)
    this._connectRetryCount = connectionOptions.ConnectRetryCount;

  //Seems like this is causing the bug because it is not inside of null-check-if for connectionOptions variable
  if (this._connectRetryCount != 1 || !ADP.IsAzureSqlServerEndpoint(connectionOptions.DataSource))
    return;
  this._connectRetryCount = 2;
}

It is somehow related to Azure and is quite different from what is available in sources.

I've posted the issue here and will wait for response.

This is a bug in (some version of) CacheConnectionStringProperties. My IL decompiler for assembly version 4.7.3056.0 shows a call to ADP.IsAzureSqlServerEndpoint(sqlConnectionString.DataSource) that is, improperly, outside the check for whether sqlConnectionString is null. It's not here, though, so I'm not sure where those bits are coming from. — Jeroen Mostert
– Jeroen Mostert, Commented May 4, 2018 at 15:16
I don't like that questions are not even being read before marked as a duplicate — adjan
– adjan, Commented May 4, 2018 at 15:20
I've adjusted the title to make it clear that it is .NET code which causes the error, not mine. Please reopen this, it is not a duplicate — Pavel K
– Pavel K, Commented May 4, 2018 at 15:32
@Evk hard to do when you can't find the relevant bug tracker. Perhaps we should use the Twitter bug tracker — Panagiotis Kanavos
– Panagiotis Kanavos, Commented May 4, 2018 at 15:44
@PanagiotisKanavos: I'm sure it's a feature that'll improve things for Azure, and it may even be a very nice feature once it works 100%, but it's more worrisome that the binary bits for this version don't appear to have any publicly available source somewhere. Either someone's private branch ended up in the build or there's still steps for building the framework bits for release that aren't documented anywhere. Neither possibility is attractive, but as long as it's a mistake and not a structural flaw it's OK. — Jeroen Mostert
– Jeroen Mostert, Commented May 4, 2018 at 16:15

Saurabh Singh · Accepted Answer · 2018-05-10 20:54:14Z

2

This is a documented known issue in System.Data in .NET Framework 4.7.2 https://github.com/Microsoft/dotnet/blob/master/releases/net472/dotnet472-known-issues.md

The issue is currently being addressed and will be available in future updates of .NET Framework 4.7.2

answered May 10, 2018 at 20:54

Saurabh Singh

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