document.BeginUpdate();

document.DocumentProperties.Creator = "John Doe";
document.DocumentProperties.Title = "Inserting Custom Properties";
document.DocumentProperties.Category = "TestDoc";
document.DocumentProperties.Description = "This code demonstrates API to modify and display standard document properties.";

document.Fields.Create(document.AppendText("\nAUTHOR: ").End, "AUTHOR");
document.Fields.Create(document.AppendText("\nTITLE: ").End, "TITLE");
document.Fields.Create(document.AppendText("\nCOMMENTS: ").End, "COMMENTS");
document.Fields.Create(document.AppendText("\nCREATEDATE: ").End, "CREATEDATE");
document.Fields.Create(document.AppendText("\nCategory: ").End, "DOCPROPERTY Category");
document.Fields.Update();
document.EndUpdate();

document.BeginUpdate()

document.DocumentProperties.Creator = "John Doe"
document.DocumentProperties.Title = "Inserting Custom Properties"
document.DocumentProperties.Category = "TestDoc"
document.DocumentProperties.Description = "This code demonstrates API to modify and display standard document properties."

document.Fields.Create(document.AppendText(vbLf & "AUTHOR: ").End, "AUTHOR")
document.Fields.Create(document.AppendText(vbLf & "TITLE: ").End, "TITLE")
document.Fields.Create(document.AppendText(vbLf & "COMMENTS: ").End, "COMMENTS")
document.Fields.Create(document.AppendText(vbLf & "CREATEDATE: ").End, "CREATEDATE")
document.Fields.Create(document.AppendText(vbLf & "Category: ").End, "DOCPROPERTY Category")
document.Fields.Update()
document.EndUpdate()

document.BeginUpdate();
    document.AppendText("A new value of MyBookmarkProperty is obtained from here: NEWVALUE!\n");
    document.Bookmarks.Create(document.FindAll("NEWVALUE!", SearchOptions.CaseSensitive)[0], "bmOne");
    document.AppendText("\nMyNumericProperty: ");
    document.Fields.Create(document.Range.End, "DOCVARIABLE CustomProperty MyNumericProperty");
    document.AppendText("\nMyStringProperty: ");
    document.Fields.Create(document.Range.End, "DOCVARIABLE CustomProperty MyStringProperty");
    document.AppendText("\nMyBooleanProperty: ");
    document.Fields.Create(document.Range.End, "DOCVARIABLE CustomProperty MyBooleanProperty");
    document.AppendText("\nMyBookmarkProperty: ");
    document.Fields.Create(document.Range.End, "DOCVARIABLE CustomProperty MyBookmarkProperty");
    document.EndUpdate();

    document.CustomProperties["MyNumericProperty"] = 123.45;
    document.CustomProperties["MyStringProperty"] = "The Final Answer";
    document.CustomProperties["MyBookmarkProperty"] = document.Bookmarks[0];
    document.CustomProperties["MyBooleanProperty"] = true;

    document.CalculateDocumentVariable += DocumentPropertyDisplayHelper.OnCalculateDocumentVariable;
    document.Fields.Update();
class DocumentPropertyDisplayHelper
{
    public static void OnCalculateDocumentVariable(object sender, DevExpress.XtraRichEdit.CalculateDocumentVariableEventArgs e)
    {
        if (e.Arguments.Count == 0 || e.VariableName != "CustomProperty")
            return;
        string name = e.Arguments[0].Value;
        var customProperty = ((DevExpress.Xpf.RichEdit.RichEditControl)sender).Document.CustomProperties[name];
        if (customProperty != null)
            e.Value = customProperty.ToString();
        e.Handled = true;
    }
}

document.BeginUpdate()
    document.AppendText("A new value of MyBookmarkProperty is obtained from here: NEWVALUE!" & vbLf)
    document.Bookmarks.Create(document.FindAll("NEWVALUE!", SearchOptions.CaseSensitive)(0), "bmOne")
    document.AppendText(vbLf & "MyNumericProperty: ")
    document.Fields.Create(document.Range.End, "DOCVARIABLE CustomProperty MyNumericProperty")
    document.AppendText(vbLf & "MyStringProperty: ")
    document.Fields.Create(document.Range.End, "DOCVARIABLE CustomProperty MyStringProperty")
    document.AppendText(vbLf & "MyBooleanProperty: ")
    document.Fields.Create(document.Range.End, "DOCVARIABLE CustomProperty MyBooleanProperty")
    document.AppendText(vbLf & "MyBookmarkProperty: ")
    document.Fields.Create(document.Range.End, "DOCVARIABLE CustomProperty MyBookmarkProperty")
    document.EndUpdate()

    document.CustomProperties("MyNumericProperty") = 123.45
    document.CustomProperties("MyStringProperty") = "The Final Answer"
    document.CustomProperties("MyBookmarkProperty") = document.Bookmarks(0)
    document.CustomProperties("MyBooleanProperty") = True

    AddHandler document.CalculateDocumentVariable, AddressOf DocumentPropertyDisplayHelper.OnCalculateDocumentVariable
    document.Fields.Update()
Private Class DocumentPropertyDisplayHelper
    Public Shared Sub OnCalculateDocumentVariable(ByVal sender As Object, ByVal e As DevExpress.XtraRichEdit.CalculateDocumentVariableEventArgs)
        If e.Arguments.Count = 0 OrElse e.VariableName <> "CustomProperty" Then
            Return
        End If
        Dim name As String = e.Arguments(0).Value
        Dim customProperty = DirectCast(sender, DevExpress.Xpf.RichEdit.RichEditControl).Document.CustomProperties(name)
        If customProperty IsNot Nothing Then
            e.Value = customProperty.ToString()
        End If
        e.Handled = True
    End Sub
End Class