Find variables with user defined attribute

Question

In a c# app how would I find all the variables in a project with a specific Attribute?

class Program
{
    static void Main()
    {
        try
        {
            using (AdsClient Client = new AdsClient())

            {
                // Connect to the TwinCAT ADS router
                Client.Connect("172.18.233.27.1.1", 851);
                //Creating a symbol loader
                SymbolLoaderSettings settings = new SymbolLoaderSettings(SymbolsLoadMode.DynamicTree);
                IAdsSymbolLoader dynLoader = (IAdsSymbolLoader)SymbolLoaderFactory.Create(Client, settings);

                // Search for symbols with a specific attribute
                string desiredAttribute = "AddToConfig";  
                
                foreach (IAdsSymbol symbol in dynLoader.Symbols)
                {
                    if ( symbol.Attributes.Contains(desiredAttribute))
                    {
                        // Perform actions on the symbol that has the attribute
                        Console.WriteLine($"Symbol Name: {symbol.InstanceName}");
                        Console.WriteLine($"Symbol Path: {symbol.InstancePath}");
                        // ... Additional actions
                    }
                }
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Error: {ex.Message}");
        }

        Console.WriteLine("Press any key to exit...");
        Console.ReadKey();
    }

I get this error.

Error: Unable to cast object of type 'TwinCAT.TypeSystem.DynamicVirtualStructInstance' to type 'TwinCAT.Ads.TypeSystem.IAdsSymbol'.

Answer 1

The code you are trying to implement requires a little bit more of recursion to find nested variables inside global variable lists or also in a POUs (Program), i had a similar situation once and i developed the following solution:

using System;
using System.Collections.Generic;
using System.Linq;
using TwinCAT;
using TwinCAT.Ads;
using TwinCAT.Ads.TypeSystem;
using TwinCAT.TypeSystem;

namespace StackOverflow
{
    internal class Program
    {
        static void Main()
        {
            try
            {
                using (AdsClient Client = new AdsClient())

                {
                    string ams = "172.18.233.27.1.1";
                    // Connect to the TwinCAT ADS router
                    Client.Connect(ams, 851);
                    //Creating a symbol loader
                    SymbolLoaderSettings settings = new SymbolLoaderSettings(SymbolsLoadMode.DynamicTree);
                    var symbolCollectionDict = (SymbolLoaderFactory.Create(Client, SymbolLoaderSettings.Default).Symbols as SymbolCollection).ToInstanceDictionary();


                    // Search for symbols with a specific attribute
                    string desiredAttribute = "AddToConfig";

                    foreach (var symbol in symbolCollectionDict)
                    {
                        var firstAttribute = symbol.Value.Attributes.FirstOrDefault(x => x.Name.Contains(desiredAttribute));

                        if (firstAttribute != null)
                        {
                            // Perform actions on the symbol that has the attribute
                            Console.WriteLine($"Symbol Name: {symbol.Key}");
                            Console.WriteLine($"Symbol Path: {symbol.Value.InstancePath}");
                            // ... Additional actions
                        }
                    }
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine($"Error: {ex.Message}");
            }

            Console.WriteLine("Press any key to exit...");
            Console.ReadKey();
        }





    }
    // This static class will define extension methods that 
    // we are calling in our program

    public static class ExtMethods
    {
        public static Dictionary<string, Instance> ToInstanceDictionary(this ISymbolCollection symbolCollection)
        {
            if (symbolCollection == null)
            {
                return new Dictionary<string, Instance>();
            }

            var dict = symbolCollection.ToDictionary(t => t.InstancePath, t => (Instance)t);

            foreach (var symbol in dict.Values.ToArray())
            {
                dict.MergeDicts(GetMemeberList(symbol));
            }

            return dict;
        }

        private static Dictionary<string, Instance> GetMemeberList(Instance symbol)
        {
            var memberInstancesPropInfo = symbol.GetType().GetProperty("MemberInstances");

            if (memberInstancesPropInfo != null)
            {
                var dict = ((ISymbolCollection)memberInstancesPropInfo.GetValue(symbol)).ToDictionary(t => t.InstancePath, t => (Instance)t);

                foreach (var internalSymbol in dict.Values.ToArray())
                {
                    dict.MergeDicts(GetMemeberList(internalSymbol));
                }

                if (dict.Count > 0)
                {
                    return dict;
                }
            }

            return new Dictionary<string, Instance>();
        }

        public static Dictionary<T1, T2> MergeDicts<T1, T2>(this Dictionary<T1, T2> masterDictionary, Dictionary<T1, T2> dictionaryToAppend)
        {

            foreach (KeyValuePair<T1, T2> keyValuePair in dictionaryToAppend)
            {
                if (masterDictionary.ContainsKey(keyValuePair.Key) == false)
                {
                    masterDictionary.Add(keyValuePair.Key, keyValuePair.Value);
                }
            }

            return masterDictionary;
        }
    }

}

The extension methods handle the recursion and generate a dictionary where you can find the variable name and instance, after that you have to loop inside the attributes until you find the required variables, i tested with a small project in twincat 3. I got the following output in the console:

which is correct!