VB.NET Requires Chilkat v11.7.0+

PDF Placeholders Without a Value: Error, Blank or Keep

See more PDF Text Replacement Examples

Demonstrates the "unusedPlaceholders" option, which decides what happens to a placeholder found on the page that has no value in "placeholders": "error" (the default) makes it a problem with the reason unusedPlaceholder, so nothing is applied; "blank" replaces it with nothing; "keep" leaves it on the page as it is. VB.NET

Dim success As Boolean = False

'  This example requires the Chilkat API to have been previously unlocked.
'  See Global Unlock Sample for sample code.

'  The PDF used in this example is available at invoice_template.pdf

Dim pdf As New Chilkat.Pdf
success = pdf.LoadFile("qa_data/pdf/invoice_template.pdf")
If (success = False) Then
    Debug.WriteLine(pdf.LastErrorText)
    Exit Sub
End If


'  Values for every placeholder except {{po}} (the purchase order number, which this customer has none of).
Dim json As New Chilkat.JsonObject
json.UpdateString("placeholders.customer","Acme Corp")
json.UpdateString("placeholders.date","2026-10-18")
json.UpdateString("placeholders.qty1","2")
json.UpdateString("placeholders.desc1","Cordless drill, 18 V")
json.UpdateString("placeholders.price1","$460.00")
json.UpdateString("placeholders.amount1","$920.00")
json.UpdateString("placeholders.qty2","6")
json.UpdateString("placeholders.desc2","Galvanized hinge, 4 inch")
json.UpdateString("placeholders.price2","$12.50")
json.UpdateString("placeholders.amount2","$75.00")
json.UpdateString("placeholders.subtotal","$995.00")
json.UpdateString("placeholders.taxRate","7.35%")
json.UpdateString("placeholders.tax","$73.13")
json.UpdateString("placeholders.total","$1,068.13")

Dim jsonOut As New Chilkat.JsonObject

'  The default, "error": the unfilled {{po}} is a problem and nothing would be applied.
success = pdf.TextReplace("check",json,jsonOut)
If (success = False) Then
    Debug.WriteLine(pdf.LastErrorText)
    Exit Sub
End If

Debug.WriteLine("error (default): ok = " & jsonOut.BoolOf("ok") & ", problem: " & jsonOut.StringOf("problems[0].field") & " " & jsonOut.StringOf("problems[0].reason"))

'  "keep": {{po}} stays on the page, literally.
json.UpdateString("unusedPlaceholders","keep")
success = pdf.TextReplace("check",json,jsonOut)
If (success = False) Then
    Debug.WriteLine(pdf.LastErrorText)
    Exit Sub
End If

Debug.WriteLine("keep: ok = " & jsonOut.BoolOf("ok"))

'  "blank": {{po}} is replaced by nothing, leaving "PO Number:" with an empty value.
json.UpdateString("unusedPlaceholders","blank")
success = pdf.TextReplace("apply",json,jsonOut)
If (success = False) Then
    Debug.WriteLine(pdf.LastErrorText)
    Exit Sub
End If

Debug.WriteLine("blank: applied = " & jsonOut.BoolOf("applied"))

success = pdf.WriteFile("qa_output/invoice_no_po.pdf")
If (success = False) Then
    Debug.WriteLine(pdf.LastErrorText)
    Exit Sub
End If


'  Sample output:

'  error (default): ok = false, problem: po unusedPlaceholder
'  keep: ok = true
'  blank: applied = true