Question

I am facing one issue with linq query in c# , my linq query as per below

list = (from row in dt.AsEnumerable()
                            select new Perfmon
                            {
                                id = row.Field<long>("id"),
                                counter1 = row.Field<string>("counter"),

                            }).ToList();

I have one perfmon class and it contains properties like (id, counter1, counter2 …)
there are more then 20 counters now i have developed sql query to select id and counter based on passed countername in parameter e.g. if i have passed counter1 then it will select id , counter1 (renamed as counter) only

if i will use switch case here then it will have 20 witch case, can anyone please help me how can bind property dynamically in linq?

Thanks in advance.

Answer 1

You can make your Perfmon class backed by a dictionary rather than fields per properties. like:

class Perfmon
{
    private readonly Dictionary<string, string> _counters = new Dictionary<string, string>();

    public Perfmon(params KeyValuePair<string, string>[] knownCounters)
    {
        foreach (var knownCounter in knownCounters)
        {
            SetCounter(knownCounter.Key, knownCounter.Value);
        }
    }   
    public void SetCounter(string name, string value)
    {
        _counters[name] = value;
    }

    protected string GetCounterValue(string name)
    {
        if (_counters.ContainsKey(name))
            return _counters[name];
        else
            return null;
    }

    public string Counter1 { get { return GetCounterValue("Counter1"); } }
    public string Counter2 { get { return GetCounterValue("Counter2"); } }
    public string Counter3 { get { return GetCounterValue("Counter3"); } }
}

The constructor is there so you can easily use it in your query like:

var counterName = "Counter2";
list = (from row in dt.AsEnumerable() 
                            select new Perfmon(new KeyValuePair<string, string>(counterName, row.Field<string>("counter")))
                            { 
                                id = row.Field<long>("id")
                            }).ToList();