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

  // Note: the following should be embedded in a QueuedTask.Run() statement
  {
    //Retrieve the desired feature class/table
    FeatureClassDefinition def = featureLayer.GetFeatureClass().GetDefinition();

    //get the desired attribute rule whose expression is to be evaluated.
    //AttributeRuleType.All, Calculation, Constraint, Validation
    AttributeRuleDefinition 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 = featureLayer.Search();

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

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

{
  // Must be called within QueuedTask.Run
  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 ...
      }
    }
  }
}