operationcontext-current-returns-null-in-a-using-clause.md

OperationContext.Current may return null when called in a using clause

Scope

Edge

Version Introduced

4.6.2

Version Reverted

Source Analyzer Status

Investigating

Change Description

xref:System.ServiceModel.OperationContext.Current?displayProperty=nameWithType may return null and a xref:System.NullReferenceException may result if all of the following conditions are true:

• You retrieve the value of the xref:System.ServiceModel.OperationContext.Current?displayProperty=nameWithType property in a method that returns a xref:System.Threading.Tasks.Task or xref:System.Threading.Tasks.Task%601.

• You instantiate the xref:System.ServiceModel.OperationContextScope object in a using clause.

• You retrieve the value of the xref:System.ServiceModel.OperationContext.Current?displayProperty=nameWithType property within the using statement. For example:

  using (new OperationContextScope(OperationContext.Current))
  {
      OperationContext context = OperationContext.Current;      // OperationContext.Current is null.
      // ...
  }

• Quirked

• Build-time break

Recommended Action

To address this issue, you can do the following:

• Modify your code as follows to instantiate a new non-null xref:System.ServiceModel.OperationContext.Current%2A object:

  OperationContext ocx = OperationContext.Current;
  using (new OperationContextScope(OperationContext.Current))
  {

    OperationContext.Current = new OperationContext(ocx.Channel);     // ... } ```

• Install the latest update to the .NET Framework 4.6.2, or upgrade to a later version of the .NET Framework. This disables the flow of the xref:System.Threading.ExecutionContext in xref:System.ServiceModel.OperationContext.Current?displayProperty=nameWithType and restores the behavior of WCF applications in the .NET Framework 4.6.1 and earlier versions. This behavior is configurable; it is equivalent to adding the following app setting to your configuration file:

  <appSettings>
      <add key="Switch.System.ServiceModel.DisableOperationContextAsyncFlow" value="true" />
  </appSettings>

  If this change is undesirable and your application depends on execution context flowing between operation contexts, you can enable its flow as follows:

  <appSettings>
      <add key="Switch.System.ServiceModel.DisableOperationContextAsyncFlow" value="false" />
  </appSettings>

Affected APIs

• P:System.ServiceModel.OperationContext.Current

Category

Windows Communication Foundation (WCF)