How to resolve variable in Linq Query c#?

Question

I have the below dynamic array

dynamic[] queueList = await queueInfo.Run.GetData<dynamic[]>(Name);

I want to get the unique values present in ImportTableName field. So, after some search I found this,

var distNames = queueList.Select(o => new {o.ImportTableName }).Distinct();

which works as expected.

But I don't want to hard code the fieldname "ImportTableName". So tried doing something like this

dynamic[] queueList = await queueInfo.Run.GetData<dynamic[]>(Name);
string tableName = "ImportTableName"
var distNames = queueList.Select(o => new {o.tableName }).Distinct();

But it doesn't work, result is just NULL. Can someone help me to achieve this ?

The second way you tried that is hard coded not the first one which worked. In first method that is property of that class and second one is hard-coded string. — Tech Yogesh, Oct 17 '18 at 05:54
@TechYogesh - I think I did not explain it properly, it is not always "ImportTableName", it can be anything. — Pரதீப், Oct 17 '18 at 05:56
Dynamic select https://stackoverflow.com/questions/16516971/linq-dynamic-select than just a `Distinct` after that. — Magnus, Oct 17 '18 at 06:02
Dynamic is not a good fit when you don't know the property names at compile time. Have you considered storing your data in dictionaries instead? — Jonas Høgh, Oct 17 '18 at 06:28
In order to answer this, we need to know how the dynamic objects are generated inside the GetData method. Using reflection works for regular .Net objects assigned to a dynamic reference, but not for e.g. ExpandoObjects. See https://stackoverflow.com/questions/4939508/get-value-of-c-sharp-dynamic-property-via-string — Jonas Høgh, Oct 17 '18 at 07:03
@alexqc - it returns `{Name = "JObject" FullName = "Newtonsoft.Json.Linq.JObject"}` — Pரதீப், Oct 17 '18 at 11:11

Slava Utesinov · Accepted Answer · 2018-10-17T12:05:01.943

2

As it is array of JObject, which has indexer, you can apply it to each element to get value of desired field:

var distNames = queueList.Select(x => x[tableName]).Distinct().ToList();

edited Oct 17 '18 at 12:05

answered Oct 17 '18 at 06:29

Slava Utesinov

13,410
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Thanks for your time. But its not working, `property` is null. – Pரதீப் Oct 17 '18 at 06:47
Try `GetField` instead of `GetProperty`, I did not know what is `ImportTableName` exactly. – Slava Utesinov Oct 17 '18 at 07:11
It is `JsonConvert.DeserializeObject` – Pரதீப் Oct 17 '18 at 11:07
Also `queueList.Select(o => o.GetType())` gives me `{Name = "JObject" FullName = "Newtonsoft.Json.Linq.JObject"}` – Pரதீப் Oct 17 '18 at 11:16
If it is JSON, you can simply cast it to `JObject` and then `GetValue` of property with `tableName` name. Look at updated answer. – Slava Utesinov Oct 17 '18 at 11:28
Thats it. Thanks for your help. – Pரதீப் Oct 17 '18 at 11:33

score 1 · Answer 2 · answered Oct 17 '18 at 07:05

1

My solution is:

    dynamic[] queueList = new dynamic[]{new { id = 1, ImportTableName = "Data"}};

    string propName = "ImportTableName";    
    var distNames = queueList.Select(d => d.GetType().GetProperty(propName).GetValue(d, null)).Distinct();

It returns as expected "Data".

answered Oct 17 '18 at 07:05

alexqc

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It works for your example, but it doesn't work on my code. Note, `GetData` returns `JsonConvert.DeserializeObject` – Pரதீப் Oct 17 '18 at 11:08

How to resolve variable in Linq Query c#?

2 Answers2