Export annotation data from PDFs in C# .NET

using GdPicturePDF gdpicturePDF = new GdPicturePDF();
gdpicturePDF.LoadFromFile(@"C:\temp\source.pdf");
// Create a `StringBuilder` variable to store data.
StringBuilder data = new StringBuilder();
// Add headers to the first line.
String[] headers = { "Index", "Annotation Type", "Contents", "Page" };
data.AppendLine(string.Join(";", headers));
// Get the number of pages.
int pageCount = gdpicturePDF.GetPageCount();
// Loop through all pages.
for(int page = 1; page <= pageCount; page++)
{
    // Select a PDF page.
    gdpicturePDF.SelectPage(page);
    int annotCount = gdpicturePDF.GetAnnotationCount();
    // Loop through all annotations.
    for (int i = 0; i < annotCount; i++)
    {
        // Get the current annotation type.
        string annotType = gdpicturePDF.GetAnnotationSubType(i);
        // Get the current annotation contents.
        string annotContents = gdpicturePDF.GetAnnotationContents(i);
        // Add a new line to the `StringBuilder` with the annotation data.
        String[] newLine = { i.ToString(), annotType.ToString(),
            annotContents.ToString(), page.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()
    gdpicturePDF.LoadFromFile("C:\temp\source.pdf")
    ' Create a `StringBuilder` variable to store data.
    Dim data As StringBuilder = New StringBuilder()
    ' Add headers to the first line.
    Dim headers = {"Index", "Annotation Type", "Contents", "Page"}
    data.AppendLine(String.Join(";", headers))
    ' Get the number of pages.
    Dim pageCount As Integer = gdpicturePDF.GetPageCount()
    ' Loop through all pages.
    For page = 1 To pageCount
        ' Select a PDF page.
        gdpicturePDF.SelectPage(page)
        Dim annotCount As Integer = gdpicturePDF.GetAnnotationCount()
        ' Loop through all annotations.
        For i = 0 To annotCount - 1
            ' Get the current annotation type.
            Dim annotType As String = gdpicturePDF.GetAnnotationSubType(i)
            ' Get the current annotation contents.
            Dim annotContents As String = gdpicturePDF.GetAnnotationContents(i)
            ' Add a new line to the `StringBuilder` with the annotation data.
            Dim newLine As String() = {i.ToString(), annotType.ToString(), annotContents.ToString(), page.ToString()}
            data.AppendLine(String.Join(";", newLine))
        Next
    Next
    ' Save the collected data to a CSV file.
    Dim formData = "C:\temp\output.csv"
    File.AppendAllText(formData, data.ToString())
End Using