## SignatureLine.ProviderId property Gets or sets signature provider identifier for this signature line. Default value is "{00000000-0000-0000-0000-000000000000}". ```csharp public Guid ProviderId ......docx"); Shape shape = (Shape)doc.GetChild(NodeType.Shape, 0, true);...true); signatureLine = shape.SignatureLine; Assert.That(signatureLine...