Extract Metadata from PDF File in C#

using (var metadata = new GroupDocs.Metadata.Metadata("input.pdf"))
{
	// extract all metadata properties that fall into a particular category
	var properties = metadata.FindProperties(
		p => p.Tags.Any(t => t.Category == GroupDocs.Metadata.Tagging.Tags.Content));

	// iterate over all properties and display
	foreach (var property in properties)
	{
		Console.WriteLine("{0} = {1}", property.Name, property.Value);
	}

	// extract all properties having a specific type and value
	var year = DateTime.Today.Year;
	properties = metadata.FindProperties(
		p => p.Value.Type == GroupDocs.Metadata.Common.MetadataPropertyType.DateTime &&
		p.Value.ToStruct(DateTime.MinValue).Year == year);

	// display all datetime properties with the year value equal to the current year
	foreach (var property in properties)
	{
		Console.WriteLine("{0} = {1}", property.Name, property.Value);
	}

	// extract all properties having names matching the specified regex
	const string pattern = "^author|company|(.+date.*)$";
	var regex = new System.Text.RegularExpressions.Regex(pattern,
		System.Text.RegularExpressions.RegexOptions.IgnoreCase);
	properties = metadata.FindProperties(p => regex.IsMatch(p.Name));

	// display properties whose names match the following pattern
	foreach (var property in properties)
	{
		Console.WriteLine("{0} = {1}", property.Name, property.Value);
	}
}