C# Find object inside List object

Question

What I am trying to do Is, find an object inside a list

Log q = logs.Find(x => (x.dnsq.queryID.Contains(queryid)));

However when I do it, I get this error

x.dnsq.queryID = 'x.dnsq.queryID' threw an exception of type 'System.NullReferenceException

The Log class looks like this

class Log : LogCtrl
{
    public int id { set; get; }
    public string source { set; get; }
    public string destination { set; get; }
    public string protocol { set; get; }
    public double time { set; get; }
    public string info { set; get; }
    public DNSresponse dnsr { set; get; }
    public DNSquery dnsq { set; get; }
}

one of your object is null or dnsq is null or queryID is null — Steve, Sep 25 '15 at 20:09

score 2 · Accepted Answer · answered Sep 25 '15 at 20:09

2

It sounds like either x or x.dnsq or x.dnsq.queryId is null for at least one item in logs. You can check for this in your statement by doing the following:

    Log q = logs.Find(x => (x != null && x.dnsq != null && x.dnsq.queryID != null && x.dnsq.queryID.Contains(queryid)));

answered Sep 25 '15 at 20:09

Maria Gullickson

53
5

Or with the new `?.` operator – Adriano Repetti Sep 25 '15 at 20:10
Well, I used the debugger to check the logs List, and I know it contains an entry where dnsq.queryID is equal to what I'm searching for. – Mathias_ Sep 25 '15 at 20:10
1

@Mathias_ doesn't matter if the list contains it or not, as long as one of the field is null it will throw null exception – Steve Sep 25 '15 at 20:11
Great, that seems to have dont the trick, thanks alot! – Mathias_ Sep 25 '15 at 20:15

C# Find object inside List object

1 Answers1