/// <summary>
/// Constructs a new <see cref="ServiceInvocationContext"/> using the specified <see cref="HttpClient"/>, <see cref="ITraceSink"/>, base URL and <see cref="CancellationToken"/>.
/// </summary>
/// <param name="httpClient">The <see cref="HttpClient"/> object to use to make Http Requests.</param>
/// <param name="trace">The <see cref="ITraceSink"/> object to write trace events to.</param>
/// <param name="baseUrl">The base URL of the <see cref="NuGetRepository"/> associated with this invocation.</param>
/// <param name="cancellationToken">A <see cref="CancellationToken"/> that can be used to check for cancellation.</param>
public ServiceInvocationContext(HttpClient httpClient, ITraceSink trace, Uri baseUrl, CancellationToken cancellationToken)
{
Guard.NotNull(httpClient, "httpClient");
Guard.NotNull(trace, "trace");
Guard.NotNull(baseUrl, "baseUrl");
InvocationId = Tracing.GetNextInvocationId().ToString(CultureInfo.InvariantCulture);
_client = httpClient;
Trace = new TraceContext(InvocationId, trace);
BaseUrl = baseUrl;
CancellationToken = cancellationToken;
Trace.Start();
}