/// <summary>
/// Get a function to access the key field of a search document.
/// </summary>
/// <param name="async">Whether to run sync or async.</param>
/// <param name="cancellationToken">The cancellation token.</param>
/// <returns>A Task representing the operation.</returns>
private async Task GetKeyFieldAccessorAsync(bool async, CancellationToken cancellationToken)
{
// Case 1: The user provided an explicit accessor and we're done
if (KeyFieldAccessor != null)
{
return;
}
// Case 2: Infer the accessor from FieldBuilder
try
{
FieldBuilder builder = new FieldBuilder {
Serializer = SearchClient.Serializer
};
IDictionary <string, SearchField> fields = builder.BuildMapping(typeof(T));
KeyValuePair <string, SearchField> keyField = fields.FirstOrDefault(pair => pair.Value.IsKey == true);
if (!keyField.Equals(default(KeyValuePair <string, SearchField>)))
{
KeyFieldAccessor = CompileAccessor(keyField.Key);
return;
}
}
catch
{
// Ignore any errors because this type might not have been
// designed with FieldBuilder in mind
}
// Case 3: Fetch the index to find the key
Exception failure = null;
try
{
// Call the service to find the name of the key
SearchIndexClient indexClient = SearchClient.GetSearchIndexClient();
SearchIndex index = async ?
await indexClient.GetIndexAsync(IndexName, cancellationToken).ConfigureAwait(false) :
indexClient.GetIndex(IndexName, cancellationToken);
SearchField keyField = index.Fields.Single(f => f.IsKey == true);
string key = keyField.Name;
if (typeof(T).IsAssignableFrom(typeof(SearchDocument)))
{
// Case 3a: If it's a dynamic SearchDocument, lookup
// the name of the key in the dictionary
KeyFieldAccessor = (T doc) => (doc as SearchDocument)?.GetString(key);
return;
}
else
{
// Case 3b: We'll see if there's a property with the
// same name and use that as the accessor
if (typeof(T).GetProperty(key) != null ||
typeof(T).GetField(key) != null)
{
KeyFieldAccessor = CompileAccessor(key);
return;
}
}
}
catch (Exception ex)
{
// We'll provide any exceptions as a hint because it could
// be something like using the wrong API Key type when
// moving from SearchClient up to SearchIndexClient that
// potentially could be addressed if the user really wanted
failure = ex;
}
// Case 4: Throw and tell the user to provide an explicit accessor.
throw new InvalidOperationException(
$"Failed to discover the Key field of document type {typeof(T).Name} for Azure Cognitive Search index {IndexName}. " +
$"Please set {typeof(SearchIndexingBufferedSenderOptions<T>).Name}.{nameof(SearchIndexingBufferedSenderOptions<T>.KeyFieldAccessor)} explicitly.",
failure);