> For the complete documentation index, see [llms.txt](https://docs.apryse.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.apryse.com/xamarin/get-started/samples/fdftest.md).

# FDF

Sample C# code for using Apryse SDK to programmatically merge forms data with the PDF in order to fill forms, or to extract form field data from the PDF. Apryse SDK has full support for Forms Data For

Sample C# code for using Apryse SDK to programmatically merge forms data with the PDF in order to fill forms, or to extract form field data from the PDF. Apryse SDK has full support for Forms Data Format (FDF).

Learn more about our full [PDF Data Extraction SDK Capabilities](https://apryse.com/capabilities/extraction).

To start your free trial, [get stated with Xamarin SDK](/xamarin/get-started/get-started.md).

{% tabs %}
{% tab title="C#" %}
{% code lineNumbers="true" %}

```csharp
//
// Copyright (c) 2001-2021 by PDFTron Systems Inc. All Rights Reserved.
//

using System;
using pdftron;
using pdftron.Common;
using pdftron.Filters;
using pdftron.SDF;
using pdftron.PDF;
using pdftron.FDF;

using NUnit.Framework;

namespace MiscellaneousSamples
{
	/// <summary>
	/// PDFNet includes full support for FDF (Forms Data Format) and for merging/extracting
	/// forms data (FDF) with/from PDF. This sample illustrates basic FDF merge/extract functionality 
	/// available in PDFNet.
	/// </summary>
	[TestFixture]
	public class FDFTest
	{
		
		/// <summary>
		/// The main entry point for the application.
		/// </summary>
		[Test]
		public static void Sample()
		{

			// Relative path to the folder containing test files.
			const string input_path =  "TestFiles/";

			// Example 1)
			// Iterate over all form fields in the document. Display all field names.
			try  
			{
				using (PDFDoc doc = new PDFDoc(Utils.GetAssetTempFile(input_path + "form1.pdf")))
				{
					doc.InitSecurityHandler();
					
					FieldIterator itr;
					for(itr=doc.GetFieldIterator(); itr.HasNext(); itr.Next())
					{
						Console.WriteLine("Field name: {0:s}", itr.Current().GetName());
						Console.WriteLine("Field partial name: {0:s}", itr.Current().GetPartialName());

						Console.Write("Field type: ");
						Field.Type type = itr.Current().GetType();
						switch(type)
						{
							case Field.Type.e_button: 
								Console.WriteLine("Button"); break;
							case Field.Type.e_check: 
								Console.WriteLine("Check"); break;
							case Field.Type.e_radio: 
								Console.WriteLine("Radio"); break;
							case Field.Type.e_text: 
								Console.WriteLine("Text"); break;
							case Field.Type.e_choice: 
								Console.WriteLine("Choice"); break;
							case Field.Type.e_signature: 
								Console.WriteLine("Signature"); break;
							case Field.Type.e_null: 
								Console.WriteLine("Null"); break;
						}

						Console.WriteLine("------------------------------");
					}

					Console.WriteLine("Done.");
				}
			}
			catch (PDFNetException e)
			{
				Console.WriteLine(e.Message);
				Assert.True(false);
			}

			// Example 2) Import XFDF into FDF, then merge data from FDF into PDF
			try  
			{
				// XFDF to FDF
				// form fields
				Console.WriteLine("Import form field data from XFDF to FDF.");
				
				FDFDoc fdf_doc1 = FDFDoc.CreateFromXFDF(Utils.GetAssetTempFile(input_path + "form1_data.xfdf"));
				fdf_doc1.Save(Utils.CreateExternalFile("form1_data.fdf"));
				
				// annotations
				Console.WriteLine("Import annotations from XFDF to FDF.");
				
				FDFDoc fdf_doc2 = FDFDoc.CreateFromXFDF(Utils.GetAssetTempFile(input_path + "form1_annots.xfdf"));
				fdf_doc2.Save(Utils.CreateExternalFile("form1_annots.fdf"));
				
				// FDF to PDF
				// form fields
				Console.WriteLine("Merge form field data from FDF.");
				
				using (PDFDoc doc = new PDFDoc(Utils.GetAssetTempFile(input_path + "form1.pdf")))
				{
					doc.InitSecurityHandler();
					doc.FDFMerge(fdf_doc1);
					
					// Refreshing missing appearances is not required here, but is recommended to make them 
					// visible in PDF viewers with incomplete annotation viewing support. (such as Chrome)
					doc.RefreshAnnotAppearances();
					
					doc.Save(Utils.CreateExternalFile("form1_filled.pdf"), SDFDoc.SaveOptions.e_linearized);
					
					// annotations
					Console.WriteLine("Merge annotations from FDF.");
					
					doc.FDFMerge(fdf_doc2);
					// Refreshing missing appearances is not required here, but is recommended to make them 
					// visible in PDF viewers with incomplete annotation viewing support. (such as Chrome)
					doc.RefreshAnnotAppearances();
					doc.Save(Utils.CreateExternalFile("form1_filled_with_annots.pdf"), SDFDoc.SaveOptions.e_linearized);

					Console.WriteLine("Done.");
				}
			}
			catch (PDFNetException e)
			{
				Console.WriteLine(e.Message);
				Assert.True(false);
			}

			// Example 3) Extract data from PDF to FDF, then export FDF as XFDF
			try  
			{
				// PDF to FDF
				using (PDFDoc in_doc = new PDFDoc(Utils.CreateExternalFile("form1_filled_with_annots.pdf")))
				{
					in_doc.InitSecurityHandler();
					
					// form fields only
					Console.WriteLine("Extract form fields data to FDF.");
					
					FDFDoc doc_fields = in_doc.FDFExtract(PDFDoc.ExtractFlag.e_forms_only);
					doc_fields.SetPdfFileName("../form1_filled_with_annots.pdf");
					doc_fields.Save(Utils.CreateExternalFile("form1_filled_data.fdf"));
					
					// annotations only
					Console.WriteLine("Extract annotations to FDF.");
					
					FDFDoc doc_annots = in_doc.FDFExtract(PDFDoc.ExtractFlag.e_annots_only);
					doc_annots.SetPdfFileName("../form1_filled_with_annots.pdf");
					doc_annots.Save(Utils.CreateExternalFile("form1_filled_annot.fdf"));
					
					// both form fields and annotations
					Console.WriteLine("Extract both form fields and annotations to FDF.");
					
					FDFDoc doc_both = in_doc.FDFExtract(PDFDoc.ExtractFlag.e_both);
					doc_both.SetPdfFileName("../form1_filled_with_annots.pdf");
					doc_both.Save(Utils.CreateExternalFile("form1_filled_both.fdf"));
					
					// FDF to XFDF
					// form fields
					Console.WriteLine("Export form field data from FDF to XFDF.");
					
					doc_fields.SaveAsXFDF(Utils.CreateExternalFile("form1_filled_data.xfdf"));
					
					// annotations
					Console.WriteLine("Export annotations from FDF to XFDF.");
					
					doc_annots.SaveAsXFDF(Utils.CreateExternalFile("form1_filled_annot.xfdf"));
					
					// both form fields and annotations
					Console.WriteLine("Export both form fields and annotations from FDF to XFDF.");
					
					doc_both.SaveAsXFDF(Utils.CreateExternalFile("form1_filled_both.xfdf"));
					
					Console.WriteLine("Done.");
				}
			}
			catch (PDFNetException e)
			{
				Console.WriteLine(e.Message);
				Assert.True(false);
			}

            // Example 4) Merge/Extract XFDF into/from PDF
            try
            {
                // Merge XFDF from string
                PDFDoc in_doc = new PDFDoc(Utils.GetAssetTempFile(input_path + "numbered.pdf"));
				{
					in_doc.InitSecurityHandler();

					Console.WriteLine("Merge XFDF string into PDF.");

					string str = "<?xml version=\"1.0\" encoding=\"UTF-8\" ?><xfdf xmlns=\"http://ns.adobe.com/xfdf\" xml:space=\"preserve\"><square subject=\"Rectangle\" page=\"0\" name=\"cf4d2e58-e9c5-2a58-5b4d-9b4b1a330e45\" title=\"user\" creationdate=\"D:20120827112326-07'00'\" date=\"D:20120827112326-07'00'\" rect=\"227.7814207650273,597.6174863387978,437.07103825136608,705.0491803278688\" color=\"#000000\" interior-color=\"#FFFF00\" flags=\"print\" width=\"1\"><popup flags=\"print,nozoom,norotate\" open=\"no\" page=\"0\" rect=\"0,792,0,792\" /></square></xfdf>";

					using (FDFDoc fdoc = FDFDoc.CreateFromXFDF(str))
					{
						in_doc.FDFMerge(fdoc);
						in_doc.Save(Utils.CreateExternalFile("numbered_modified.pdf"), SDFDoc.SaveOptions.e_linearized);
						Console.WriteLine("Merge complete.");
					}

					// Extract XFDF as string
					Console.WriteLine("Extract XFDF as a string.");
					FDFDoc fdoc_new = in_doc.FDFExtract(PDFDoc.ExtractFlag.e_both);
					string XFDF_str = fdoc_new.SaveAsXFDF();
					Console.WriteLine("Extracted XFDF: ");
					Console.WriteLine(XFDF_str);
					Console.WriteLine("Extract complete.");
				}
            }
            catch (PDFNetException e)
            {
                Console.WriteLine(e.Message);
                Assert.True(false);
            }

			// Example 5) Read FDF files directly
			try  
			{
				FDFDoc doc = new FDFDoc(Utils.CreateExternalFile("form1_filled_data.fdf"));
				FDFFieldIterator itr = doc.GetFieldIterator();
				for(; itr.HasNext(); itr.Next()) 
				{
					Console.WriteLine("Field name: {0:s}", itr.Current().GetName());
					Console.WriteLine("Field partial name: {0:s}", itr.Current().GetPartialName());
					Console.WriteLine("------------------------------");
				}

				Console.WriteLine("Done.");
			}
			catch (PDFNetException e)
			{
				Console.WriteLine(e.Message);
				Assert.True(false);
			}

			// Example 6) Direct generation of FDF.
			try  
			{
				FDFDoc doc = new FDFDoc();

				// Create new fields (i.e. key/value pairs).
				doc.FieldCreate("Company", (int)Field.Type.e_text, "PDFTron Systems");
				doc.FieldCreate("First Name", (int)Field.Type.e_text, "John");
				doc.FieldCreate("Last Name", (int)Field.Type.e_text, "Doe");
				// ...		

				// doc.SetPdfFileName("mydoc.pdf");
				doc.Save(Utils.CreateExternalFile("sample_output.fdf"));
				Console.WriteLine("Done. Results saved in sample_output.fdf");
			}
			catch (PDFNetException e)
			{
				Console.WriteLine(e.Message);
				Assert.True(false);
			}
		}
	}
}
```

{% endcode %}
{% endtab %}
{% endtabs %}


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