> 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/forms/import-data.md). # Merge Form Data File (FDF or XFDF) to PDF Forms in Xamarin Learn how to efficiently merge XFDF or FDF annotations into PDF documents using FDFUpdate, FDFMerge, and MergeXFDF APIs. Choose the best method for your use case and optimize your PDF workflow. The Ap Depending on the type and origin of the XFDF or FDF, one of the following methods should be used: 1. Replace all annotations in the PDF document with the annotations from XFDF or FDF using [FDFUpdate](https://docs.apryse.com) API. 2. Add all annotations from XFDF or FDF to the PDF document using [FDFMerge](https://docs.apryse.com) API (potentially introducing duplicates). 3. Merge XFDF directly into the PDF document using [MergeXFDF](https://docs.apryse.com) API (introduced in PDFNet 9.2) * In order for the API to function, annotations in XFDF should be named ([see below](https://docs.apryse.com)) * `MergeXFDF` API is the recommended solution for command XFDF files See below, which API is best suited to the given [use case](https://docs.apryse.com). ### Replacing all annotations in the document This is a 2-step process: first XFDF needs to be converted into FDF, then FDF needs to be passed to `FDFUpdate` API. As a result of the import operation, the PDF document will have all annotations from XFDF and no other: 1. Annotations that are in XFDF only will be added 2. Annotations that are both in XFDF and PDF will be modified as needed 3. Annotations that are **only** in PDF and not in XFDF will be removed `FDFUpdate` API works best for the scenarios like restoring annotations from a backup. Also it would be a good option when bringing in annotations creating in WebViewer, i.e. use `FDFUpdate` to import XFDF written by WebViewer. {% hint style="warning" %} Note, *FDFUpdate* should be used **only** for the full XFDF files exported by Apryse API (Apryse SDK or WebViewer) from the same document. This method is not applicable to partial (incomplete) XFDF, because all the annotations that are not included in XFDF will be **removed** from the document. If XFDF was created by another tool, all widgets will be removed. {% endhint %} {% tabs %} {% tab title="C#" %} {% code lineNumbers="true" %} ```csharp // Import annotations from XFDF to FDF FDFDoc fdf_doc = new FDFDoc(FDFDoc.CreateFromXFDF(xfdf_filename)); // Optionally read XFDF from a string FDFDoc fdf_doc = new FDFDoc(FDFDoc.CreateFromXFDF(xfdf_string)); // Merge FDF data into PDF doc PDFDoc doc = new PDFDoc(filename); doc.FDFUpdate(fdf_doc); ``` {% endcode %} {% endtab %} {% endtabs %} ### Adding all annotations from XFDF This is a 2-step process: first XFDF needs to be converted into FDF, then FDF needs to be passed to `FDFMerge` API. As a result of the import operation, **all** the XFDF annotations will be added to the PDF document: 1. Annotations that are in XFDF only will be added 2. Annotations that are both in XFDF and PDF will also be added, i.e. duplicating those annotations 3. Annotations that are only in PDF and not in XFDF will not be modified `FDFMerge` API works best for bringing new annotations into a document from a partial XFDF and for adding annotations to an empty PDF document. {% hint style="warning" %} Note, *FDFMerge* does not modify the existing annotations. When an annotation is present in both XFDF and PDF, it will be duplicated. {% endhint %} It also works well for importing field-only XFDF (e.g. field data exported from other PDF solutions). {% hint style="info" %} \*\* Duplicate prevention \*\* To prevent duplicates, remove all the annotations expected to be present in the PDF document from XFDF before using *FDFMerge* API. {% endhint %} ### Merging XFDF directly into the PDF This is a 1-step process: XFDF is passed directly to `MergeXFDF` API. The API can both add and modify the annotations, but not delete them (except when using a command file). : 1. Annotations that are in XFDF only will be added 2. Annotations that are both in XFDF and PDF will be modified (see below) 3. Annotations that are only in PDF and not in XFDF will not be modified {% hint style="warning" %} Note, *MergeXFDF* API relies on annotation names for matching the annotations. If XFDF file contains unnamed annotation, merge operation will be aborted with an exception. In order to proceed, set *Force* option, some annotations may be duplicated. {% endhint %} {% hint style="info" %} \*\* Name generation \*\* XFDF files exported using PDFNet API version 9.0 and higher always contain annotation names, even if the annotations in the PDF document don't have them. When imported, those annotations will still be matched correctly. {% endhint %} `MergeXFDF` is also the API that should be used with command files (a flavor of XFDF with add-delete-modify instructions, see `GetAnnotCommand`() or [`AnnotationManager.exportAnnotCommand`](https://sdk.apryse.com/api/web/Core.AnnotationManager.html#exportAnnotCommand__anchor) in WebViewer). In case of command XFDF, all operations specified by the command file, including deletions will be performed on the document. ### Common use cases | Use case | API | | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------- | | Restoring annotations from backup | `FDFUpdate` | | Importing all changes made to annotations in WebViewer | `FDFUpdate` | | Importing form data exported from other PDF solutions | `FDFMerge` or `MergeXFDF` | | Introducing several new annotations to a document while keeping the existing document's annotations | `FDFMerge` or `MergeXFDF` | | Importing partial XFDF that contains modifications to annotations that already exist in the document (assuming XFDF annotations are named) | `MergeXFDF` | | Importing [command xfdf file](https://www.apryse.com/blog/annotation/how-to-export-xfdf-annotations/#how-to-export-xfdf-from-pdf-with-javascript), which allows fast application of annotation changes made on another WebViewer or Apryse SDK instance. | `MergeXFDF` | [PDF Form fill and form data extraction](/xamarin/get-started/samples.md#fdf) Full sample code which illustrates basic FDF merge/extract functionality and full support for FDF (Forms Data Format) --- # Agent Instructions This documentation is published with GitBook. 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