LINQ to JSON - Select array object element where specific property matches

Question

MY LINQ-Fu skills pretty bad and after looking at JSON.NET examples I am still having trouble figuring out how to select that data I am after. I have a blob of JSON as follows ...

{
    "@odata.context": "http://wabi-us-north-central-b-redirect.analysis.windows.net/v1.0/myorg/$metadata#groups",
    "@odata.count": 2,
    "value": [
        {
            "id": "z48856e6-f385-4c89-a4b8-33c24hsr5c",
            "isReadOnly": false,
            "isOnDedicatedCapacity": false,
            "name": "Blood Values"
        },
        {
            "id": "k95d7cfe-c2a5-41f9-804w-e1b7ab31g31k",
            "isReadOnly": false,
            "isOnDedicatedCapacity": false,
            "name": "Tissue Preps"
        }
    ]
}

I am trying to write a LINQ to JSON expression that will allow me to select the value of the id element where the name value is equal to `Tissue Preps'.

var parsedJson = JObject.Parse(webResponse.Response);
var datasetId = parsedJson["value"].Select(i => i.SelectToken("id")).Where(n => n.SelectToken("name").ToString() == "Tissue Preps");

Above is the LINQ expression I tried but I end up getting a Object reference not set to an instance of an object. error. I would like to avoid having to write a class to represent the JSON so it can be deserialized.

I think your first Select is going to remove everything except token "id", which means there is "name" to use in the Where - what is it there for? — NetMage
– NetMage, Commented Jul 13, 2018 at 20:04
I tried putting the Where first but got the same results. var groupId = parsedJson["value"].Where(y => y.SelectToken("name").ToString() == groupName).Select(x => x.SelectToken("id"));. I want to grab the id property of the element in the value array where the name property is Tissue Preps — webworm
– webworm, Commented Jul 13, 2018 at 20:27
What type do you want GroupId to be? What if more than one member of "value" has the name of "Tissue Preps"? The Select definitely needs to go to the end. Are you sure that error is on this line, I don't see how? — NetMage
– NetMage, Commented Jul 13, 2018 at 20:41
groupId will be a string. There will not be any cases where more than one has the same name value. Basicaly I am trying to find the identifier based on the name — webworm
– webworm, Commented Jul 13, 2018 at 20:42
The return type from Select is? I believe you want First instead of Where. — NetMage
– NetMage, Commented Jul 13, 2018 at 20:43

NetMage · Accepted Answer · 2018-07-16 23:01:22Z

1

Since you expect a single answer and not an IEnumerable, you need to use First:

var parsedJson = JObject.Parse(webResponse.Response);
var datasetId = parsedJson["value"].First(n => n.SelectToken("name").ToString() == "Tissue Preps")
                                   .SelectToken("id")
                                   .ToString();

edited Jul 16, 2018 at 23:01

answered Jul 16, 2018 at 17:40

NetMage

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