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// For complete examples and data files, please go to https://github.com/groupdocs-annotation/GroupDocs.Annotation-for-.NET
// Create instance of annotator. 
AnnotationConfig cfg = CommonUtilities.GetConfiguration();

AnnotationImageHandler annotator = new AnnotationImageHandler(cfg);

IDocumentDataHandler documentRepository = annotator.GetDocumentDataHandler();
if (!Directory.Exists(cfg.StoragePath))
{
    Directory.CreateDirectory(cfg.StoragePath);
}

// Create document data object in storage.
var document = documentRepository.GetDocument("Document.pdf");
long documentId = document != null ? document.Id : annotator.CreateDocument("Document.pdf");

// Create annotation object
AnnotationInfo textFieldAnnotation = new AnnotationInfo
{
    AnnotationPosition = new Point(852.0, 201.0),
    FieldText = "text in the box",
    FontFamily = "Arial",
    FontSize = 10,
    Box = new Rectangle(66f, 201f, 64f, 37f),
    PageNumber = 0,
    Type = AnnotationType.TextField,
    CreatorName = "Anonym",
    DocumentGuid = documentId
};

//Add annotation to storage
CreateAnnotationResult createTextFieldAnnotationResult = annotator.CreateAnnotation(textFieldAnnotation);

// Set background color of annotation
SaveAnnotationTextResult setBackgroundColorResult = annotator.SetAnnotationBackgroundColor(createTextFieldAnnotationResult.Id, 16711680);