How to get single values from am gremlinquery in C# code - azure

Question

I am using gremlin with Azure Cosmos DB. I'm using this code to get a list of files from a graph database.
public async Task<List<string>> GetFilesWithMoreThanOneFilename()
{
List<string> list = new List<string>();
using (var gremlinClient = new GremlinClient(gremlinServer, new GraphSON2Reader(), new GraphSON2Writer(), GremlinClient.GraphSON2MimeType))
{
var resultSet = await gremlinClient.SubmitAsync<dynamic>("g.V().hasLabel('file').where(out().count().is(gt(1)))");
if (resultSet.Count > 0)
{
foreach (var result in resultSet)
{
string output = JsonConvert.SerializeObject(result);
list.Add(output);
}
}
}
return list;
}
The output string looks like this:
{"id":"0a37e4896b6310b6d152f6cf89336173ffb89b819f7955494322e0f0bec017b4","label":"file","type":"vertex","properties":{"fileSize":[{"id":"456b087c-7cf3-43ea-a482-0f31219bc520","value":"41096"}],"mimeType":[{"id":"d849b065-16f8-465b-986c-f8e0fdda9ac7","value":"text/plain"}]}}
My Question is how I can get a single value from the result. For example just the ID or the mimeType or is the only possiblity to work with the output and string manipulation?

Answer 1

Due to your output data is in json format, so you could use Newtonsoft.Json to read the data.
I create a json file with your data, you could just parse the json data without file. And just read the id and properties.fileSize
static void Main(string[] args)
{
JObject jsonData = JObject.Parse(File.ReadAllText( "test.json"));
Console.WriteLine("id:"+jsonData["id"].ToString());
Console.WriteLine("properties:"+jsonData["properties"]["fileSize"].ToString());
Console.ReadLine();
}
And here is the result:
Hope this could help you, if yo ustill have other questions, please let me know.
Update: if you want to get the value in the array, you could use this to get the value:
Console.WriteLine("mimeType.value:" + jsonData["properties"]["mimeType"][0]["value"].ToString());

Answer 2

In general, you should only retrieve the values that you actually need and not vertices with all their properties and then filter locally. This is equivalent to relational databases where you wouldn't usually do SELECT * and instead do something like SELECT name.
Additionally, you should specify the return type you're expecting which allows Gremlin.NET to deserialize the result for you so you don't have to do that yourself.
These two suggestions together give you something like this:
var names = await client.SubmitAsync<string>(
"g.V().hasLabel('person').where(out().count().is(gt(1))).values('name')");
Console.WriteLine($"First name: {names.First()}");
names is then just a ResultSet<string> which implements IReadOnlyCollection<string>.