Extract data from PDF form fields in C# .NET

using GdPicturePDF gdpicturePDF = new GdPicturePDF();

// Create a `StringBuilder` variable to store data.
StringBuilder data = new StringBuilder();
// Add headers to the first line.
String[] headers = {"Field ID", "Field Type", "Field Location Page"};
data.AppendLine(string.Join(";", headers));

gdpicturePDF.LoadFromFile(@"C:\temp\source.pdf");
// Get the form field count.
int fieldCount = gdpicturePDF.GetFormFieldsCount();
// Loop through all form fields.
for (int i = 0; i < fieldCount; i++)
{
    // Get the field ID, type, and page location of each form field.
    int fieldID = gdpicturePDF.GetFormFieldId(i);
    PdfFormFieldType fieldType = gdpicturePDF.GetFormFieldType(fieldID);
    int location = gdpicturePDF.GetFormFieldPage(fieldID);
    // Add a new line to the `StringBuilder` with the form field data.
    String[] newLine = { fieldID.ToString(), fieldType.ToString(), location.ToString() };
    data.AppendLine(string.Join(";", newLine));
}
// Save the collected data to a CSV file.
String formData = @"C:\temp\output.csv";
File.AppendAllText(formData, data.ToString());

Using gdpicturePDF As GdPicturePDF = New GdPicturePDF()
    ' Create a `StringBuilder` variable to store data.
    Dim data As StringBuilder = New StringBuilder()
    ' Add headers to the first line.
    Dim headers = {"Field ID", "Field Type", "Field Location Page"}
    data.AppendLine(String.Join(";", headers))

    gdpicturePDF.LoadFromFile("C:\temp\source.pdf")
    ' Get the form field count.
    Dim fieldCount As Integer = gdpicturePDF.GetFormFieldsCount()
    ' Loop through all form fields.
    For i = 0 To fieldCount - 1
        ' Get the field ID, type, and page location of each form field.
        Dim fieldID As Integer = gdpicturePDF.GetFormFieldId(i)
        Dim fieldType As PdfFormFieldType = gdpicturePDF.GetFormFieldType(fieldID)
        Dim location As Integer = gdpicturePDF.GetFormFieldPage(fieldID)
        ' Add a new line to the `StringBuilder` with the form field data.
        Dim newLine As String() = {fieldID.ToString(), fieldType.ToString(), location.ToString()}
        data.AppendLine(String.Join(";", newLine))
    Next
    ' Save the collected data to a CSV file.
    Dim formData = "C:\temp\output.csv"
    File.AppendAllText(formData, data.ToString())
End Using