public string GetScriptExpression()

//Consult https://github.com/Esri/arcade-expressions/ and
//https://developers.arcgis.com/arcade/profiles/attribute-rules/ for
//more examples and arcade reference

QueuedTask.Run(() =>
{
  //Retrieve the desired feature class/table
  var def = featLayer.GetFeatureClass().GetDefinition();
  
  //get the desired attribute rule whose expression is to be
  //evaluated.
  //AttributeRuleType.All, Calculation, Constraint, Validation
  var validation_rule = def.GetAttributeRules(
                              AttributeRuleType.Validation).FirstOrDefault();
  if (validation_rule == null)
    return;

  //Get the expression
  var expr = validation_rule.GetScriptExpression();
  //construct a CIMExpressionInfo
  var arcade_expr = new CIMExpressionInfo()
  {
    Expression = expr,
    //Return type can be string, numeric, or default
    ReturnType = ExpressionReturnType.Default
  };

  System.Diagnostics.Debug.WriteLine($"Evaluating {expr}:");
  //Construct an evaluator
  //we are using ArcadeProfile.AttributeRules profile...
  //Consult: https://developers.arcgis.com/arcade/profiles/
  using (var arcade = ArcadeScriptEngine.Instance.CreateEvaluator(
                          arcade_expr, ArcadeProfile.AttributeRuleValidation))
  {
    //we are evaluating the expression against all features
    using (var rc = featLayer.Search())
    {

      while (rc.MoveNext())
      {
        //Provision  values for any profile variables referenced...
        //in our case we assume '$feature'
        //...use arcade.ProfileVariablesUsed() if necessary...
        var variables = new List<KeyValuePair<string, object>>() {
          new KeyValuePair<string, object>("$feature", rc.Current)
        };

        //evaluate the expression per feature
        try
        {
          var result = arcade.Evaluate(variables).GetResult();
          //'Validation' attribute rules return true or false...
          var valid = System.Boolean.Parse(result.ToString());
          System.Diagnostics.Debug.WriteLine(
            $"{rc.Current.GetObjectID()} valid: {valid}");
        }
        //handle any exceptions
        catch (InvalidProfileVariableException ipe)
        {
          //something wrong with the profile variable specified
          //TODO...
        }
        catch (EvaluationException ee)
        {
          //something wrong with the query evaluation
          //TODO...
        }
      }
    }
  }
});

public void GetAttributeRules(Geodatabase geodatabase, string tableName)
{
    using (TableDefinition tableDefinition = geodatabase.GetDefinition<TableDefinition>(tableName))
    {
        // Get all attribute rule types
        IReadOnlyList<AttributeRuleDefinition> ruleDefinitions = tableDefinition.GetAttributeRules();

        // Iterate rule definitions
        foreach (AttributeRuleDefinition ruleDefinition in ruleDefinitions)
        {
            AttributeRuleType ruleType = ruleDefinition.GetAttributeRuleType();
            string ruleDescription = ruleDefinition.GetDescription();
            bool isAttributeFieldEditable = ruleDefinition.GetIsFieldEditable();
            string arcadeVersionToSupportRule = ruleDefinition.GetMinimumArcadeVersion();
            int ruleEvaluationOrder = ruleDefinition.GetEvaluationOrder();
            AttributeRuleTriggers triggeringEvents = ruleDefinition.GetTriggeringEvents();
            string scriptExpression = ruleDefinition.GetScriptExpression();

            // more properties
        }
    }
}