Get value from JToken that may not exist (best practices)

Question

This is pretty much what the generic method Value() is for. You get exactly the behavior you want if you combine it with nullable value types and the ?? operator:

width = jToken.Value<double?>("width") ?? 100;

I would write GetValue as below

public static T GetValue<T>(this JToken jToken, string key, T defaultValue = default(T))
{
    dynamic ret = jToken[key];
    if (ret == null) return defaultValue;
    if (ret is JObject) return JsonConvert.DeserializeObject<T>(ret.ToString());
    return (T)ret;
}

This way you can get the value of not only the basic types but also complex objects. Here is a sample

public class ClassA
{
    public int I;
    public double D;
    public ClassB ClassB;
}
public class ClassB
{
    public int I;
    public string S;
}

var jt = JToken.Parse("{ I:1, D:3.5, ClassB:{I:2, S:'test'} }");

int i1 = jt.GetValue<int>("I");
double d1 = jt.GetValue<double>("D");
ClassB b = jt.GetValue<ClassB>("ClassB");

Here is how you can check if the token exists:

if (jobject["Result"].SelectToken("Items") != null) { ... }

It checks if "Items" exists in "Result".

This is a NOT working example that causes exception:

if (jobject["Result"]["Items"] != null) { ... }

You can simply typecast, and it will do the conversion for you, e.g.

var with = (double?) jToken[key] ?? 100;

It will automatically return null if said key is not present in the object, so there's no need to test for it.