Hi
I think that you should use Documentbuilder class to insert FormField into the document. For example see the following code.
Dim doc As Document = New Document()
Dim builder As DocumentBuilder = New DocumentBuilder(doc)
Dim shape1 As Shape = New Shape(doc, ShapeType.TextBox)
shape1.Width = 200
shape1.Height = 50
doc.Sections(0).Body.FirstParagraph.AppendChild(shape1)
Dim par1 As Paragraph = New Paragraph(doc)
Dim run1 As Run = New Run(doc)
run1.Text = ""
par1.AppendChild(run1)
shape1.AppendChild(par1)
builder.MoveTo(run1)
'Insert Text input
builder.InsertTextInput("Input1", TextFormFieldType.RegularText, "", "test", 1024)
builder.InsertBreak(BreakType.LineBreak)
'InsertCheckBox
builder.InsertCheckBox("Check1", False, 10)
builder.InsertBreak(BreakType.LineBreak)
'Insert Combobox
builder.InsertComboBox("Combo1", New String() {"test1", "test2"}, 0)
doc.Save("out.doc")
I hope that this will help you.
Best regards.