[net48] Upgrading 3rd-party library causes System.Configuration.ConfigurationErrorsException.

[msfcolombo]

Description

Upgrading 3rd-party library causes error reading app.config.

This is related to this issue: Azure/azure-cosmos-dotnet-v3#5148.

The Azure/azure-cosmos-dotnet-v3 team could not root cause and asked me to create a ticket for dotnet/runtime team.

The following error happens after upgrading to Cosmos DB SDK v3:
 

Failed to create database: System.Configuration.ConfigurationErrorsException: Configuration system failed to initialize ---> System.Configuration.ConfigurationErrorsException: Unrecognized configuration section system.diagnostics. (<redacted.exe.config> line 464)
   at System.Configuration.ConfigurationSchemaErrors.ThrowIfErrors(Boolean ignoreLocal)
   at System.Configuration.BaseConfigurationRecord.ThrowIfParseErrors(ConfigurationSchemaErrors schemaErrors)
   at System.Configuration.ClientConfigurationSystem.EnsureInit(String configKey)
   --- End of inner exception stack trace ---
   at System.Configuration.ConfigurationManager.PrepareConfigSystem()
   at System.Configuration.ConfigurationManager.GetSection(String sectionName)
   at System.Configuration.ConfigurationManager.get_AppSettings()
   at Microsoft.Azure.Cosmos.DocumentClient.Initialize(Uri serviceEndpoint, ConnectionPolicy connectionPolicy, Nullable`1 desiredConsistencyLevel, HttpMessageHandler handler, ISessionContainer sessionContainer, Nullable`1 enableCpuMonitor, IStoreClientFactory storeClientFactory, TokenCredential tokenCredential, String cosmosClientId, RemoteCertificateValidationCallback remoteCertificateValidationCallback, CosmosClientTelemetryOptions cosmosClientTelemetryOptions)
   at Microsoft.Azure.Cosmos.DocumentClient..ctor(Uri serviceEndpoint, AuthorizationTokenProvider cosmosAuthorization, EventHandler`1 sendingRequestEventArgs, ConnectionPolicy connectionPolicy, Nullable`1 desiredConsistencyLevel, JsonSerializerSettings serializerSettings, ApiType apitype, EventHandler`1 receivedResponseEventArgs, HttpMessageHandler handler, ISessionContainer sessionContainer, Nullable`1 enableCpuMonitor, Func`2 transportClientHandlerFactory, IStoreClientFactory storeClientFactory, Boolean isLocalQuorumConsistency, String cosmosClientId, RemoteCertificateValidationCallback remoteCertificateValidationCallback, CosmosClientTelemetryOptions cosmosClientTelemetryOptions, IChaosInterceptorFactory chaosInterceptorFactory)
   at Microsoft.Azure.Cosmos.ClientContextCore.Create(CosmosClient cosmosClient, CosmosClientOptions clientOptions)
   at Microsoft.Azure.Cosmos.CosmosClient..ctor(String accountEndpoint, AuthorizationTokenProvider authorizationTokenProvider, CosmosClientOptions clientOptions)

This is a legacy system that uses net48. We did attempt to remove settings, but we ended up losing telemetry. Please help us root causing this.

Reproduction Steps

Confidential. Please contact me for bug reproduction steps.

Expected behavior

No exception should not be thrown.

Actual behavior

The exception is thrown.

Regression?

No response

Known Workarounds

No response

Configuration

No response

Other information

No response

[dotnet-policy-service]

Tagging subscribers to this area: @dotnet/area-system-configuration
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[tarekgh]

we need a repro to be able to help with that. Could you please provide that?

Following up with @msfcolombo offline

[tarekgh]

Here are the results of my investigation.

• The failing application references an updated version of the Cosmos DB library. It targets .NET Framework 4.8 and includes a system.diagnostics element in its application configuration file to enable telemetry.

<configuration>
  <system.diagnostics>
  --> details are omitted
  </system.diagnostics>
</configuration>

• To support the system.diagnostics configuration, it's typically necessary to define a corresponding <section> element in the configuration file. This specifies the assembly and type responsible for handling diagnostics. For example:

<section name="system.diagnostics" type="System.Diagnostics.SystemDiagnosticsSection, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />

• The system.diagnostics section is typically defined in the machine.config file, which is located at a path similar to %windir%\Microsoft.NET\Framework64\v4.0.30319\Config\machine.config for .NET Framework 4.x installations.
• The updated Cosmos DB library now depends on System.Configuration.ConfigurationManager, which may impact how configuration settings—such as system.diagnostics—are processed in .NET Framework applications.
• Since the code accesses appSettings via ConfigurationManager, it forces the configuration system to load and parse the relevant config files in order to return the correct settings.
• The ConfigurationManager does not appear to load machine.config from its standard location %windir%\Microsoft.NET\Framework64\v4.0.30319\Config\machine.config. Instead, it attempts to locate the file in the application's base directory AppDomain.BaseDirectory. You can see this behavior in the code referenced here.
• In the absence of a machine.config file in the application’s base directory, ConfigurationManager defaults to an internal, hardcoded configuration string to simulate the expected machine.config structure.
• The hardcoded contents used by ConfigurationManager in place of machine.config are missing the system.diagnostics section definition when targeting .NET Framework. As a result, ConfigurationManager is unable to process the system.diagnostics element defined in the application's app.config, leading to a runtime exception indicating that the section is missing. This behavior aligns with the failure we’re observing.

The simplest workaround is to place the machine.config file inside a folder named Config located at the root of the application. I’ve already tested this approach, and it successfully resolved the issue. Here is sample machine.config file to use:

<configuration>
    <configSections>
        <section name='appSettings' type='System.Configuration.AppSettingsSection, System.Configuration.ConfigurationManager' restartOnExternalChanges='false' requirePermission='false' />
        <section name='connectionStrings' type='System.Configuration.ConnectionStringsSection, System.Configuration.ConfigurationManager' requirePermission='false' />
        <section name='mscorlib' type='System.Configuration.IgnoreSection, System.Configuration.ConfigurationManager' allowLocation='false' />
        <section name='runtime' type='System.Configuration.IgnoreSection, System.Configuration.ConfigurationManager' allowLocation='false' />
        <section name='assemblyBinding' type='System.Configuration.IgnoreSection, System.Configuration.ConfigurationManager' allowLocation='false' />
        <section name='satelliteassemblies' type='System.Configuration.IgnoreSection, System.Configuration.ConfigurationManager' allowLocation='false' />
        <section name='startup' type='System.Configuration.IgnoreSection, System.Configuration.ConfigurationManager' allowLocation='false' />
        <section name="system.diagnostics" type="System.Diagnostics.SystemDiagnosticsSection, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
        <section name='system.runtime.remoting' type='System.Configuration.IgnoreSection, System.Configuration.ConfigurationManager' allowLocation='false' />
        <section name='windows' type='System.Configuration.IgnoreSection, System.Configuration.ConfigurationManager' allowLocation='false' />
    </configSections>
    <configProtectedData defaultProvider='RsaProtectedConfigurationProvider'>
        <providers>
            <add name = 'RsaProtectedConfigurationProvider' type='System.Configuration.RsaProtectedConfigurationProvider, System.Configuration.ConfigurationManager' description='Uses RsaCryptoServiceProvider to encrypt and decrypt' keyContainerName='NetFrameworkConfigurationKey' cspProviderName='' useMachineContainer='true' useOAEP='false' />
            <add name = 'DataProtectionConfigurationProvider' type='System.Configuration.DpapiProtectedConfigurationProvider, System.Configuration.ConfigurationManager' description='Uses CryptProtectData and CryptUnProtectData Windows APIs to encrypt and decrypt' useMachineProtection='true' keyEntropy='' />
        </providers>
    </configProtectedData>
    <connectionStrings>
        <add name = 'LocalSqlServer' connectionString='data source=.\SQLEXPRESS;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|aspnetdb.mdf;User Instance=true' providerName='System.Data.SqlClient' />
    </connectionStrings>
</configuration>