How to check if dynamic is empty.

Question

I am using Newtonsoft's Json.NET to deserialize a JSON string:

var output = JsonConvert.DeserializeObject<dynamic>("{ 'foo': 'bar' }");

How can I check that output is empty? An example test case:

var output = JsonConvert.DeserializeObject<dynamic>("{ }");
Assert.IsNull(output); // fails

Solution 1

The object you get back from DeserializeObject is going to be a JObject, which has a Count property. This property tells you how many properties are on the object.

var output = JsonConvert.DeserializeObject<dynamic>("{ }");

if (((JObject)output).Count == 0)
{
    // The object is empty
}

This won't tell you if a dynamic object is empty, but it will tell you if a deserialized JSON object is empty.

Solution 2

You can also check with following code:

var output = JsonConvert.DeserializeObject<dynamic>("{ }");
if (output as JObject == null)
{
}

That worked for me.

Comments

[Kirk Woll]

According to the docs, DeserializeObject returns T, which will not be a JObject.

[James Newton-King]

dynamic is not an actual type so Json.NET falls back to using JObject.

[Hilton Giesenow]

I had to do something similar today and this helped, but I needed to adjust it to: ((JToken)output).Count()