The WAAPI C# sample implementation using WampSharp included in 2017.1 and 2018.1 is very hard to use and we don't recommend using it anymore.
Instead, we recommend using the Audiokinetic implementation provided with 2019.1. It is compatible with 2017.1 Authoring.
To get it, download the most recent version of Wwise (2019.1.1+) and use the folder \SDK\samples\WwiseAuthoringAPI\cs. Here is an example:
https://www.audiokinetic.com/library/edge/?source=SDK&id=wamp__cs.html
Here is an example with the new C# API:
// Query the volume, using JObject constructor
var query = new JObject(
new JProperty("from", new JObject(
new JProperty("id", new JArray(new string[] { testObj["id"].ToString() })))));
var options = new JObject(
new JProperty("return", new string[] { "name", "id", "@Volume" }));
JObject result = await client.Call(ak.wwise.core.@object.get, query, options);
System.Console.WriteLine(result["return"][0]["@Volume"]);
There is also version of Call which takes JSON string directly.