FieldCollection Class

public class FieldCollection : IEnumerable<Field>, 
	IEnumerable

Public Class FieldCollection
	Implements IEnumerable(Of Field), IEnumerable

public ref class FieldCollection : IEnumerable<Field^>, 
	IEnumerable

type FieldCollection =  
    class
        interface IEnumerable<Field>
        interface IEnumerable
    end

public void FieldCollection()
{
    // Create a new document and insert some fields
    Document doc = new Document();
    DocumentBuilder builder = new DocumentBuilder(doc);

    builder.InsertField(" DATE \\@ \"dddd, d MMMM yyyy\" ");
    builder.InsertField(" TIME ");
    builder.InsertField(" REVNUM ");
    builder.InsertField(" AUTHOR  \"John Doe\" ");
    builder.InsertField(" SUBJECT \"My Subject\" ");
    builder.InsertField(" QUOTE \"Hello world!\" ");
    doc.UpdateFields();

    // Get the collection that contains all the fields in a document
    FieldCollection fields = doc.Range.Fields;
    Assert.AreEqual(6, fields.Count);

    // Iterate over the field collection and print contents and type of every field using a custom visitor implementation
    FieldVisitor fieldVisitor = new FieldVisitor();

    using (IEnumerator<Field> fieldEnumerator = fields.GetEnumerator())
    {
        while (fieldEnumerator.MoveNext())
        {
            if (fieldEnumerator.Current != null)
            {
                fieldEnumerator.Current.Start.Accept(fieldVisitor);
                fieldEnumerator.Current.Separator?.Accept(fieldVisitor);
                fieldEnumerator.Current.End.Accept(fieldVisitor);
            }
            else
            {
                Console.WriteLine("There are no fields in the document.");
            }
        }
    }

    Console.WriteLine(fieldVisitor.GetText());

    // Get a field to remove itself
    fields[0].Remove();
    Assert.AreEqual(5, fields.Count);

    // Remove a field by reference
    Field lastField = fields[3];
    fields.Remove(lastField);
    Assert.AreEqual(4, fields.Count);

    // Remove a field by index
    fields.RemoveAt(2);
    Assert.AreEqual(3, fields.Count);

    // Remove all fields from the document
    fields.Clear();
    Assert.AreEqual(0, fields.Count);
}

/// <summary>
/// Document visitor implementation that prints field info.
/// </summary>
public class FieldVisitor : DocumentVisitor
{
    public FieldVisitor()
    {
        mBuilder = new StringBuilder();
    }

    /// <summary>
    /// Gets the plain text of the document that was accumulated by the visitor.
    /// </summary>
    public string GetText()
    {
        return mBuilder.ToString();
    }

    /// <summary>
    /// Called when a FieldStart node is encountered in the document.
    /// </summary>
    public override VisitorAction VisitFieldStart(FieldStart fieldStart)
    {
        mBuilder.AppendLine("Found field: " + fieldStart.FieldType);
        mBuilder.AppendLine("\tField code: " + fieldStart.GetField().GetFieldCode());
        mBuilder.AppendLine("\tDisplayed as: " + fieldStart.GetField().Result);

        return VisitorAction.Continue;
    }

    /// <summary>
    /// Called when a FieldSeparator node is encountered in the document.
    /// </summary>
    public override VisitorAction VisitFieldSeparator(FieldSeparator fieldSeparator)
    {
        mBuilder.AppendLine("\tFound separator: " + fieldSeparator.GetText());

        return VisitorAction.Continue;
    }

    /// <summary>
    /// Called when a FieldEnd node is encountered in the document.
    /// </summary>
    public override VisitorAction VisitFieldEnd(FieldEnd fieldEnd)
    {
        mBuilder.AppendLine("End of field: " + fieldEnd.FieldType);

        return VisitorAction.Continue;
    }

    private readonly StringBuilder mBuilder;
}