/// <summary>
/// Retrieves the metadata block or item identified by a metadata query expression.
/// </summary>
/// <param name="name">The query expression to the requested metadata block or item.</param>
/// <param name="value">The metadata block or item requested or null if not found.</param>
/// <returns>True when the metadata block or item was found, otherwise false.</returns>
/// <remarks>
/// GetMetadataByName uses metadata query expressions to access embedded metadata. For more information on the metadata query language, see the Metadata Query Language Overview.
/// <br/>
/// If multiple blocks or items exist that are expressed by the same query expression, the first metadata block or item found will be returned.
/// </remarks>
public static bool TryGetMetadataByName(this IWICMetadataQueryReader metadataQueryReader, string name, out object?value)
{
if (metadataQueryReader is null)
{
throw new NullReferenceException();
}
if (name is null)
{
throw new ArgumentNullException(nameof(name));
}
var variant = new PROPVARIANT();
try
{
metadataQueryReader.GetMetadataByName(name, ref variant);
value = PropVariantHelper.Decode(variant);
return(true);
}
catch (COMException ex) when(ex.ErrorCode == WinCodecError.PROPERTY_NOT_FOUND)
{
value = null;
return(false);
}
finally
{
PropVariantHelper.Free(variant);
}
}
/// <summary>
/// Retrieves the metadata block or item identified by a metadata query expression.
/// </summary>
/// <param name="name">The query expression to the requested metadata block or item.</param>
/// <returns>The metadata block or item requested.</returns>
/// <exception cref="COMException">Thrown when the metadata block or item was not found (HRESULT 0x88982F40).</exception>
/// <remarks>
/// GetMetadataByName uses metadata query expressions to access embedded metadata. For more information on the metadata query language, see the Metadata Query Language Overview.
/// <br/>
/// If multiple blocks or items exist that are expressed by the same query expression, the first metadata block or item found will be returned.
/// </remarks>
public static object GetMetadataByName(this IWICMetadataQueryReader metadataQueryReader, string name)
{
if (metadataQueryReader is null)
{
throw new NullReferenceException();
}
if (name is null)
{
throw new ArgumentNullException(nameof(name));
}
var variant = new PROPVARIANT();
try
{
metadataQueryReader.GetMetadataByName(name, ref variant);
return(PropVariantHelper.Decode(variant));
}
finally
{
PropVariantHelper.Free(variant);
}
}