Fill Form Fields in PDF File in C#

We have already demonstrated how to create form fields in PDF file. This article mainly shows you how developers fill form field in PDF in C# only with 3 simple steps by using a standalone .NET PDF component Spire.PDF.

Make sure Spire.PDF for .NET has been installed correctly and then add Spire.Pdf.dll as reference in the downloaded Bin folder though the below path: "..\Spire.Pdf\Bin\NET4.0\ Spire.Pdf.dll". Here comes to the details of how developers Fill Form Fields by using Spire.PDF:

Step 1: Open the form that needs to fill the data

[C#]
//Create a pdf document
PdfDocument doc = new PdfDocument();
//Load from file
doc.LoadFromFile(@"..\..\FormField.pdf");

Step 2: Update the data to the form

[C#]
//Get form
PdfFormWidget formWidget = doc.Form as PdfFormWidget;
for (int i = 0; i < formWidget.FieldsWidget.List.Count; i++)
            {
                PdfField field = formWidget.FieldsWidget.List[i] as PdfField;


//Fill the data for textBoxField
if (field is PdfTextBoxFieldWidget)
   {
    PdfTextBoxFieldWidget textBoxField = field as PdfTextBoxFieldWidget;
    switch (textBoxField.Name)
     {

     case "email":
        textBoxField.Text = "support@e-iceblue.com";
    break;
     case "password":
        textBoxField.Password = true;
        textBoxField.Text = "e-iceblue";

//Fill the data for listBoxField
if (field is PdfListBoxWidgetFieldWidget)
  {
     PdfListBoxWidgetFieldWidget listBoxField = field as PdfListBoxWidgetFieldWidget;
     switch (listBoxField.Name)
       {

        case "email_format":
         int[] index = { 1 };
         listBoxField.SelectedIndex = index;
         break;


//Fill the data for comBoxField
if (field is PdfComboBoxWidgetFieldWidget)
  {
   PdfComboBoxWidgetFieldWidget comBoxField = field as PdfComboBoxWidgetFieldWidget;
   switch (comBoxField.Name)
    {

     case "title":
       int[] items = { 0 };
       comBoxField.SelectedIndex = items;
       break;


//Fill the data for checkBoxField
if (field is PdfCheckBoxWidgetFieldWidget)
  {
   PdfCheckBoxWidgetFieldWidget checkBoxField = field as PdfCheckBoxWidgetFieldWidget;
   switch (checkBoxField.Name)
    {

    case "agreement_of_terms":
      checkBoxField.Checked = true;
      break;

Step 3: Save and launch file

[C#]
//Save the document to file in PDF format
doc.SaveToFile(@"../../FormFieldData.pdf.pdf");
//Launch the file
System.Diagnostics.Process.Start(@"../../FormFieldData.pdf.pdf");

Effective Screenshot:

The original PDF with form fields:

before fill form fields

After fill the form fields:

after fill form fields

View the full code as below:

C#
using Spire.Pdf;
using Spire.Pdf.Fields;
using Spire.Pdf.Widget;


namespace FillFormFields
{
    class Program
    {
        static void Main(string []args){
            PdfDocument doc = new PdfDocument();
            doc.LoadFromFile(@"..\..\FormField.pdf");
            PdfFormWidget formWidget = doc.Form as PdfFormWidget;
            for (int i = 0; i < formWidget.FieldsWidget.List.Count; i++)
            {
                PdfField field = formWidget.FieldsWidget.List[i] as PdfField;
                if (field is PdfTextBoxFieldWidget)
                {
                    PdfTextBoxFieldWidget textBoxField = field as PdfTextBoxFieldWidget;
                    switch (textBoxField.Name)
                    {
                        case "email":
                            textBoxField.Text = "support@e-iceblue.com";
                            break;
                        case "username":
                            textBoxField.Text = "E-iceblue";
                            break;
                        case "password":
                            textBoxField.Password = true;
                            textBoxField.Text = "e-iceblue";
                            break;
                        case "password2":
                            textBoxField.Password = true;
                            textBoxField.Text = "e-iceblue";
                            break;
                        case "company_name ":
                            textBoxField.Text = "E-iceblue";
                            break;
                        case "first_name":
                            textBoxField.Text = "James";
                            break;
                        case "last_name":
                            textBoxField.Text = "Chen";
                            break;
                        case "middle_name":
                            textBoxField.Text = "J";
                            break;
                        case "address1":
                            textBoxField.Text = "Chengdu";
                            break;
                        case "address2":
                            textBoxField.Text = "Beijing";
                            break;
                        case "city":
                            textBoxField.Text = "Shanghai";
                            break;
                        case "postal_code":
                            textBoxField.Text = "11111";
                            break;
                        case "state":
                            textBoxField.Text = "Shanghai";
                            break;
                        case "phone":
                            textBoxField.Text = "1234567901";
                            break;
                        case "mobile_phone":
                            textBoxField.Text = "123456789";
                            break;
                        case "fax":
                            textBoxField.Text = "12121212";
                            break;
                    }
                }
                if (field is PdfListBoxWidgetFieldWidget)
                {
                    PdfListBoxWidgetFieldWidget listBoxField = field as PdfListBoxWidgetFieldWidget;
                    switch (listBoxField.Name)
                    {
                        case "email_format":
                            int[] index = { 1 };
                            listBoxField.SelectedIndex = index;
                            break;
                    }
                }

                if (field is PdfComboBoxWidgetFieldWidget)
                {
                    PdfComboBoxWidgetFieldWidget comBoxField = field as PdfComboBoxWidgetFieldWidget;
                    switch (comBoxField.Name)
                    {
                        case "title":
                            int[] items = { 0 };
                            comBoxField.SelectedIndex = items;
                            break;
                    }
                }

                if (field is PdfRadioButtonListFieldWidget)
                {
                    PdfRadioButtonListFieldWidget radioBtnField = field as PdfRadioButtonListFieldWidget;
                    switch (radioBtnField.Name)
                    {
                        case "country":
                            radioBtnField.SelectedIndex = 1;
                            break;
                    }
                }

                if (field is PdfCheckBoxWidgetFieldWidget)
                {
                    PdfCheckBoxWidgetFieldWidget checkBoxField = field as PdfCheckBoxWidgetFieldWidget;
                    switch (checkBoxField.Name)
                    {
                        case "agreement_of_terms":
                            checkBoxField.Checked = true;
                            break;
                    }
                }
                if (field is PdfButtonWidgetFieldWidget)
                {
                    PdfButtonWidgetFieldWidget btnField = field as PdfButtonWidgetFieldWidget;
                    switch (btnField.Name)
                    {
                        case "submit":
                            btnField.Text = "Submit";
                            break;
                    }
                }
            }
            doc.SaveToFile(@"../../FormFieldData.pdf.pdf");
            System.Diagnostics.Process.Start(@"../../FormFieldData.pdf.pdf");
        }
    }
}
VB.NET
Imports Spire.Pdf
Imports Spire.Pdf.Fields
Imports Spire.Pdf.Widget


Namespace FillFormFields
	Class Program
		Private Shared Sub Main(args As String())
			Dim doc As New PdfDocument()
			doc.LoadFromFile("..\..\FormField.pdf")
			Dim formWidget As PdfFormWidget = TryCast(doc.Form, PdfFormWidget)
			For i As Integer = 0 To formWidget.FieldsWidget.List.Count - 1
				Dim field As PdfField = TryCast(formWidget.FieldsWidget.List(i), PdfField)
				If TypeOf field Is PdfTextBoxFieldWidget Then
					Dim textBoxField As PdfTextBoxFieldWidget = TryCast(field, PdfTextBoxFieldWidget)
					Select Case textBoxField.Name
						Case "email"
							textBoxField.Text = "support@e-iceblue.com"
							Exit Select
						Case "username"
							textBoxField.Text = "E-iceblue"
							Exit Select
						Case "password"
							textBoxField.Password = True
							textBoxField.Text = "e-iceblue"
							Exit Select
						Case "password2"
							textBoxField.Password = True
							textBoxField.Text = "e-iceblue"
							Exit Select
						Case "company_name "
							textBoxField.Text = "E-iceblue"
							Exit Select
						Case "first_name"
							textBoxField.Text = "James"
							Exit Select
						Case "last_name"
							textBoxField.Text = "Chen"
							Exit Select
						Case "middle_name"
							textBoxField.Text = "J"
							Exit Select
						Case "address1"
							textBoxField.Text = "Chengdu"
							Exit Select
						Case "address2"
							textBoxField.Text = "Beijing"
							Exit Select
						Case "city"
							textBoxField.Text = "Shanghai"
							Exit Select
						Case "postal_code"
							textBoxField.Text = "11111"
							Exit Select
						Case "state"
							textBoxField.Text = "Shanghai"
							Exit Select
						Case "phone"
							textBoxField.Text = "1234567901"
							Exit Select
						Case "mobile_phone"
							textBoxField.Text = "123456789"
							Exit Select
						Case "fax"
							textBoxField.Text = "12121212"
							Exit Select
					End Select
				End If
				If TypeOf field Is PdfListBoxWidgetFieldWidget Then
					Dim listBoxField As PdfListBoxWidgetFieldWidget = TryCast(field, PdfListBoxWidgetFieldWidget)
					Select Case listBoxField.Name
						Case "email_format"
							Dim index As Integer() = {1}
							listBoxField.SelectedIndex = index
							Exit Select
					End Select
				End If

				If TypeOf field Is PdfComboBoxWidgetFieldWidget Then
					Dim comBoxField As PdfComboBoxWidgetFieldWidget = TryCast(field, PdfComboBoxWidgetFieldWidget)
					Select Case comBoxField.Name
						Case "title"
							Dim items As Integer() = {0}
							comBoxField.SelectedIndex = items
							Exit Select
					End Select
				End If

				If TypeOf field Is PdfRadioButtonListFieldWidget Then
					Dim radioBtnField As PdfRadioButtonListFieldWidget = TryCast(field, PdfRadioButtonListFieldWidget)
					Select Case radioBtnField.Name
						Case "country"
							radioBtnField.SelectedIndex = 1
							Exit Select
					End Select
				End If

				If TypeOf field Is PdfCheckBoxWidgetFieldWidget Then
					Dim checkBoxField As PdfCheckBoxWidgetFieldWidget = TryCast(field, PdfCheckBoxWidgetFieldWidget)
					Select Case checkBoxField.Name
						Case "agreement_of_terms"
							checkBoxField.Checked = True
							Exit Select
					End Select
				End If
				If TypeOf field Is PdfButtonWidgetFieldWidget Then
					Dim btnField As PdfButtonWidgetFieldWidget = TryCast(field, PdfButtonWidgetFieldWidget)
					Select Case btnField.Name
						Case "submit"
							btnField.Text = "Submit"
							Exit Select
					End Select
				End If
			Next
			doc.SaveToFile("../../FormFieldData.pdf.pdf")
			System.Diagnostics.Process.Start("../../FormFieldData.pdf.pdf")
		End Sub
	End Class
End Namespace