/// <summary>
/// This method is invoked by the data services framework to retrieve the default stream associated
/// with the Entity Type specified by the <paramref name="entity"/> parameter.
/// Note that we set the response ETag in the host object before we return.
/// </summary>
/// <param name="entity">The stream returned should be the default stream associated with this entity.</param>
/// <param name="operationContext">A reference to the context for the current operation.</param>
/// <returns>A valid stream the data service use to query / read a streamed BLOB which is associated with the <paramref name="entity"/>.</returns>
internal Stream GetReadStream(object entity, DataServiceOperationContext operationContext)
{
Debug.Assert(entity != null, "entity != null");
Debug.Assert(operationContext != null, "operationContext != null");
string etagFromHeader;
bool? checkETagForEquality;
DataServiceStreamProviderWrapper.GetETagFromHeaders(operationContext, out etagFromHeader, out checkETagForEquality);
Debug.Assert(
string.IsNullOrEmpty(etagFromHeader) && !checkETagForEquality.HasValue || !string.IsNullOrEmpty(etagFromHeader) && checkETagForEquality.HasValue,
"etag and checkETagForEquality parameters must both be set or not set at the same time.");
Stream readStream = null;
try
{
readStream = InvokeApiCallAndValidateHeaders("IDataServiceStreamProvider.GetReadStream", () => this.StreamProvider.GetReadStream(entity, etagFromHeader, checkETagForEquality, operationContext), operationContext);
}
catch (DataServiceException e)
{
if (e.StatusCode == (int)System.Net.HttpStatusCode.NotModified)
{
// For status code 304, we MUST set the etag value. Our Error handler will translate
// DataServiceException(304) to a normal response with status code 304 and an empty message-body.
#if DEBUG
WebUtil.WriteETagValueInResponseHeader(null, this.GetStreamETag(entity, operationContext), operationContext.Host);
#else
WebUtil.WriteETagValueInResponseHeader(this.GetStreamETag(entity, operationContext), operationContext.Host);
#endif
}
throw;
}
try
{
if (readStream == null || !readStream.CanRead)
{
throw new InvalidOperationException(Strings.DataService_InvalidStreamFromGetReadStream);
}
// GetStreamETag can throw and we need to catch and dispose the stream.
#if DEBUG
WebUtil.WriteETagValueInResponseHeader(null, this.GetStreamETag(entity, operationContext), operationContext.Host);
#else
WebUtil.WriteETagValueInResponseHeader(this.GetStreamETag(entity, operationContext), operationContext.Host);
#endif
}
catch
{
WebUtil.Dispose(readStream);
throw;
}
return(readStream);
}
/// <summary>
/// This method is invoked by the data services framework whenever an insert or update operation is
/// being processed for the stream associated with the Entity Type specified via the entity parameter.
/// </summary>
/// <param name="entity">The stream returned should be the default stream associated with this entity.</param>
/// <param name="operationContext">A reference to the context for the current operation.</param>
/// <returns>A valid stream the data service use to write the contents of a BLOB which is associated with <paramref name="entity"/>.</returns>
internal Stream GetWriteStream(object entity, DataServiceOperationContext operationContext)
{
Debug.Assert(entity != null, "entity != null");
Debug.Assert(operationContext != null, "operationContext != null");
string etag;
bool? checkETagForEquality;
DataServiceStreamProviderWrapper.GetETagFromHeaders(operationContext, out etag, out checkETagForEquality);
Debug.Assert(
string.IsNullOrEmpty(etag) && !checkETagForEquality.HasValue || !string.IsNullOrEmpty(etag) && checkETagForEquality.HasValue,
"etag and checkETagForEquality parameters must both be set or not set at the same time.");
Stream writeStream = InvokeApiCallAndValidateHeaders("IDataServiceStreamProvider.GetWriteStream", () => this.StreamProvider.GetWriteStream(entity, etag, checkETagForEquality, operationContext), operationContext);
if (writeStream == null || !writeStream.CanWrite)
{
WebUtil.Dispose(writeStream);
throw new InvalidOperationException(Strings.DataService_InvalidStreamFromGetWriteStream);
}
return(writeStream);
}