acad-fields

name	acad-fields
description	Dynamic text fields — field codes, evaluation, embedding in MText/attributes

AutoCAD Fields (Dynamic Text)

Use this skill when creating or managing field objects - dynamic text that updates based on object properties, system variables, dates, formulas, or other data sources.

Field Class

Namespace: Autodesk.AutoCAD.DatabaseServices Base class: DBObject

Creating a Field

// Create a field that shows the current date
Field dateField = new Field("%<\\AcVar Date \\f \"M/d/yyyy\">%");

// Create a field that shows an object property
Field propField = new Field(
    string.Format("%<\\AcObjProp Object(%<\\_ObjId {0}>%).Area \\f \"%lu2%pr2\">%",
        entityId.Handle));

// Set evaluation options
dateField.EvaluationOption = FieldEvaluationOptions.OnOpen
    | FieldEvaluationOptions.OnSave
    | FieldEvaluationOptions.OnPlot;

// Evaluate the field
dateField.Evaluate();

Common Field Code Patterns

// Object property (area of a polyline)
string areaField = string.Format(
    "%<\\AcObjProp Object(%<\\_ObjId {0}>%).Area \\f \"%lu2%pr2\">%",
    entity.Handle);

// System variable
string dateField = "%<\\AcVar Date \\f \"M/d/yyyy\">%";
string fileNameField = "%<\\AcVar FileName>%";
string scaleField = "%<\\AcVar CANNOSCALE \\f \"%sc\">%";

// Formula field
string formulaField = "%<\\AcExpr (1 + 2) * 3>%";

// Sheet set fields
string sheetTitle = "%<\\AcSm SheetSet.Title>%";
string sheetNumber = "%<\\AcSm Sheet.Number>%";

// Diesel expression
string dieselField = "%<\\AcDiesel $(getvar,dwgname)>%";

Embedding Fields in MText

MText mtext = new MText();
// Embed a field in MText content using field code syntax
mtext.Contents = "Area: %<\\AcObjProp Object(%<\\_ObjId "
    + entity.Handle + ">%).Area \\f \"%lu2%pr2\">%";

FieldCodeWithChildren

For managing nested/compound fields. Implements IDisposable — always Dispose() when done.

using (FieldCodeWithChildren fcc = field.GetFieldCodeWithChildren())
{
    string code = fcc.FieldCode;
    Field[] children = fcc.Children;

    // Modify
    fcc.FieldCode = "new field code";
    fcc.Add(0, childField);  // add child at index

    field.SetFieldCodeWithChildren(fcc);
}  // Dispose() called automatically

Evaluation Status

FieldEvaluationStatusResult status = field.EvaluationStatus;
FieldEvaluationStatus evalStatus = status.Status;
int errorCode = status.ErrorCode;
string errorMsg = status.ErrorMessage;

// Construct status manually
var result = new FieldEvaluationStatusResult(
    FieldEvaluationStatus.Success, 0, "");

Enums

FieldEvaluationOptions (flags): Disable=0, OnOpen=1, OnSave=2, OnPlot=4, OnEtransmit=8, OnRegen=16, OnDemand=32, Automatic=63

FieldEvaluationStatus: NotYetEvaluated=1, Success=2, EvaluatorNotFound=4, SyntaxError=8, InvalidCode=16, InvalidContext=32, OtherError=64

FieldEvaluationContext: Open=1, Save=2, Plot=4, Etransmit=8, Regen=16, Demand=32, Preview=64

FieldState (flags): Initialized=1, Compiled=2, Modified=4, Evaluated=8, HasCache=16, HasFormattedString=32

FieldCodeFlags (flags): FieldCode=1, EvaluatedText=2, EvaluatedChildren=4, ObjectReference=8, AddMarkers=16, EscapeBackslash=32, StripOptions=64, PreserveFields=128, TextField=256

FieldFilingOptions (flags): SkipFilingResult=1

Gotchas

• Field codes use %< and >% as delimiters - these MUST be present
• Object references in field codes use Handle values (not ObjectId) - handles are persistent across sessions, ObjectIds are not
• Evaluate() must be called explicitly for programmatically created fields; automatic evaluation only happens based on EvaluationOption triggers
• ConvertToTextField() permanently freezes the field - it cannot be converted back to a dynamic field
• Field codes are case-sensitive for evaluator names (\\AcVar, \\AcObjProp, \\AcExpr, etc.)
• Nested fields (fields within field codes) use %<\\_ObjId>% syntax for object references
• GetFieldCode() without flags returns the raw field code; use FieldCodeFlags.EvaluatedText to get the current display value
• The \\f format specifier in field codes uses AutoCAD format strings, not .NET format strings

Related Skills

• acad-mtext — embedding fields in MText content
• acad-tables — field content in table cells
• acad-blocks — embedding fields in attribute definitions