How to add HTTP headers in a WCF service call

Example.cs

public void PerformSoapCall() {
  using (var client = new SomeClient())
  using (new OperationContextScope(client.InnerChannel))
  {
      HttpRequestMessageProperty requestMessage = new HttpRequestMessageProperty();
      requestMessage.Headers["Authorization"] = "Basic 521vYmFsUGF5bWVudEdhdGV3YXk6R1BHMTIz22==";
      OperationContext.Current.OutgoingMessageProperties[HttpRequestMessageProperty.Name] = requestMessage;
      
      var res = await client.SomethingAsync();
  }
}