Write to form fields in PDF

 BackgroundColor="LightGray">

    <ContentPage.Content>

        <AbsoluteLayout>

            <button:SfButton x:Name="Bekijken" Text="PDF"  AbsoluteLayout.LayoutBounds=".90,.49,.30,.08" AbsoluteLayout.LayoutFlags="All" FontSize="Medium" TextColor="White" BackgroundColor="Gray" BackgroundImage="Assortiment" HorizontalTextAlignment="Center" Clicked="OnBekijkenButtonClicked"  />

            <Entry x:Name="Plaats"

                   AbsoluteLayout.LayoutBounds=".100,.49,.35,.08" AbsoluteLayout.LayoutFlags="All"

    Placeholder="" />

         

        </AbsoluteLayout>

    </ContentPage.Content>

</ContentPage>

  void OnBekijkenButtonClicked(object sender, EventArgs args)

        {

            Stream docStream = typeof(App).GetTypeInfo().Assembly.GetManifestResourceStream("Document.Boord.pdf");

            PdfLoadedDocument loadedDocument = new PdfLoadedDocument(docStream);

            //Loads the form

            PdfLoadedForm form = loadedDocument.Form;

            //Fills the textbox field by using index

            

            (form.Fields["f1_01(0)"] as PdfLoadedTextBoxField).Text = Plaats.Text;

           

            //Save the PDF document to stream.

            MemoryStream stream = new MemoryStream();

            loadedDocument.Save(stream);

            //Close the document.

            loadedDocument.Close(false);

        }

            loadedDocument.Form.Flatten = true;

            //Flattens the first field //form.Fields[0].Flatten = true;

            //Add the form field to the document

            loadedDocument.Form.Fields.Add(loadedTextBoxField);

System.ArgumentNullException

  Message=Value cannot be null.

Parameter name: file

  void OnButtonClicked(object sender, EventArgs args)

        {

            //Load PDF 

            Stream docStream = typeof(App).GetTypeInfo().Assembly.GetManifestResourceStream("GettingStarted.Assets.Boord.pdf");

            PdfLoadedDocument loadedDocument = new PdfLoadedDocument(docStream);

            //Get the loaded form

            PdfLoadedForm loadedForm = loadedDocument.Form;

            //Get the loaded text box field and fill it

            PdfLoadedTextBoxField loadedTextBoxField = loadedForm.Fields[0] as PdfLoadedTextBoxField;

            loadedTextBoxField.Text = "First Name";

            loadedDocument.Form.Flatten = true;

            //Flattens the first field //form.Fields[0].Flatten = true;

            //Add the form field to the document

            loadedDocument.Form.Fields.Add(loadedTextBoxField);

            //Save the document to the stream

            MemoryStream stream = new MemoryStream();

            loadedDocument.Save(stream);

            //Close the document

            loadedDocument.Close(true);

            //Save the stream as a file in the device and invoke it for viewing

            Xamarin.Forms.DependencyService.Get<ISave>().SaveAndView("Output.pdf", "application/pdf", stream);

        }

System.ArgumentNullException

  Message=Value cannot be null.

Parameter name: text

 void OnBekijkenButtonClicked(object sender, EventArgs args)

        {

            Stream docStream = typeof(App).GetTypeInfo().Assembly.GetManifestResourceStream("Document.Boord.pdf");

            PdfLoadedDocument loadedDocument = new PdfLoadedDocument(docStream);

            //Loads the form

            PdfLoadedForm form = loadedDocument.Form;

            //Fills the textbox field by using index

            

            (form.Fields["f1_01(0)"] as PdfLoadedTextBoxField).Text = Plaats.Text;

           

            //Save the PDF document to stream.

            MemoryStream stream = new MemoryStream();

            loadedDocument.Save(stream);

            //Close the document.

            loadedDocument.Close(false);

        }