bool ShowCodes { get; set; }

Property ShowCodes As Boolean

using DevExpress.XtraRichEdit;
using DevExpress.XtraRichEdit.API.Native;
//...

using (RichEditDocumentServer wordProcessor = new RichEditDocumentServer())
{
    // Access a document.
    Document document = wordProcessor.Document;

    // Load a document from the file.
    document.LoadDocument("MailMergeSimple.docx", DocumentFormat.Docx);

    // Check all fields in the main document body.
    for (int i = 0; i < document.Fields.Count; i++)
    {
        // Show field codes.
        document.Fields[i].ShowCodes = true;
    }
}

Imports DevExpress.XtraRichEdit
Imports DevExpress.XtraRichEdit.API.Native
'...

Using wordProcessor As New RichEditDocumentServer()
    ' Access a document.
    Dim document As Document = wordProcessor.Document

    ' Load a document from the file.
    document.LoadDocument("MailMergeSimple.docx", DocumentFormat.Docx)

    ' Check all fields in the main document body.
    For i As Integer = 0 To document.Fields.Count - 1
        ' Show field codes.
        document.Fields(i).ShowCodes = True
    Next i
End Using

doc.BeginUpdate();
foreach (Field f in doc.Fields) f.ShowCodes = true;
doc.EndUpdate();

doc.BeginUpdate();
foreach (Field f in doc.Fields) f.ShowCodes = showCodes;
doc.EndUpdate();

{
    document.Fields[i].ShowCodes = true;
}

{
    document.Fields[i].ShowCodes = true;
}

// Show field codes.
    document.Fields[i].ShowCodes = true;
}

For Each f As Field In doc.Fields
    f.ShowCodes = True
Next

For Each f As Field In doc.Fields
    f.ShowCodes = showCodes
Next

For i As Integer = 0 To document.Fields.Count - 1
    document.Fields(CInt((i))).ShowCodes = True
Next

For i As Integer = 0 To document.Fields.Count - 1
    document.Fields(i).ShowCodes = True
Next i

' Show field codes.
    document.Fields(CInt((i))).ShowCodes = True
Next