/// <summary>
/// Gets the context URI for the specified ODataPayloadElement.
/// </summary>
/// <param name="payloadElement">The annotated payload element to get the context URI for.</param>
/// <returns>The context URI from the annotated payload element or null if no context URI annotation exists.</returns>
/// <remarks>If not context URI annotation is found on the <paramref name="payloadElement"/>, this
/// method will try to compute the context URI from the expected type annotation. If successful,
/// it will cache the computed context URI as annotation on the payload element.</remarks>
public static string ContextUri(this ODataPayloadElement payloadElement)
{
ExceptionUtilities.CheckArgumentNotNull(payloadElement, "payloadElement");
JsonLightContextUriAnnotation contextUriAnnotation = (JsonLightContextUriAnnotation)payloadElement.GetAnnotation(typeof(JsonLightContextUriAnnotation));
string contextUri = null;
bool cacheContextUri = false;
// If an explicit context URI exists, return it
if (contextUriAnnotation != null)
{
contextUri = contextUriAnnotation.ContextUri;
}
else
{
// Otherwise construct a context URI from the expected type annotation
ExpectedTypeODataPayloadElementAnnotation expectedTypeAnnotation =
(ExpectedTypeODataPayloadElementAnnotation)payloadElement.GetAnnotation(typeof(ExpectedTypeODataPayloadElementAnnotation));
if (expectedTypeAnnotation != null)
{
// Construct a context URI from the exptected type annotation
JsonLightMetadataDocumentUriAnnotation metadataDocumentUriAnnotation =
(JsonLightMetadataDocumentUriAnnotation)payloadElement.GetAnnotation(typeof(JsonLightMetadataDocumentUriAnnotation));
string metadataDocumentUri = metadataDocumentUriAnnotation == null
? JsonLightConstants.DefaultMetadataDocumentUri.AbsoluteUri
: metadataDocumentUriAnnotation.MetadataDocumentUri;
string projectionString = null;
JsonLightContextUriProjectionAnnotation contextUriProjectionAnnotation = (JsonLightContextUriProjectionAnnotation)payloadElement.GetAnnotation(typeof(JsonLightContextUriProjectionAnnotation));
if (contextUriProjectionAnnotation != null)
{
// If we have a context URI projection, apply it to the context URI if the context URI does not already have one.
projectionString = contextUriProjectionAnnotation.ContextUriProjection;
Regex contextUriSelectExpandPattern = new Regex(@"(?:(?<!#Collection))\(.*\)");
// A 'null' projection string means that all properties should be projected.
if (projectionString != null)
{
bool hasProjection = contextUriSelectExpandPattern.IsMatch(projectionString);
if (!hasProjection)
{
// Inject the projection string into the context URI
projectionString = JsonLightConstants.ContextUriProjectionStart + projectionString + JsonLightConstants.ContextUriProjectionEnd;
}
}
}
contextUri = BuildContextUri(payloadElement.ElementType, metadataDocumentUri, expectedTypeAnnotation, projectionString);
cacheContextUri = true;
}
}
// Cache the computed context URI on the payload element (non-comparable annotation)
if (cacheContextUri)
{
payloadElement.WithContextUri(contextUri);
payloadElement.RemoveAnnotations(typeof(JsonLightContextUriProjectionAnnotation));
}
return(contextUri);
}