Retrieving an array from JSON in ASP.net C#

Question

I'm gathering data from a web API which returns a complex JSON string. This contains values of many different types, a few arrays, and some fairly deep nesting.

Currently I'm converting the string to a dynamic object like so:

dynamic dynamicObject = JsonConvert.DeserializeObject(jsonString);

Then I'm retrieving values from this object as needed and typecasting them, however this method gives a null reference exception when I attempt to retrieve an array:

int myValue         = (int)dynamicObject.foo.value; // Works!
int[] myArrayOfInts = (int[])dynamicObject.bar.values; // Null

I'm not sure how to proceed as I'm fairly new to C# and ASP.net. Most of the solutions I have come across so far require the creation of small, strictly-typed classes which mirror the entire JSON structure. In my case it would be preferable to simply use a dynamic object, partly for simplicity and partly because only certain values are actually being used.

Answer 1

When I try to run your code, I get a RuntimeBinderException: Cannot convert type 'Newtonsoft.Json.Linq.JArray' to 'int[]' . You can do this conversion with ToObject .

dynamic dynamicObject = JsonConvert.DeserializeObject("{\"values\": [1, 3, 4]}");
int[] myArrayOfInts = dynamicObject.values.ToObject<int[]>();

The cast to int works because a casting conversion is defined for many types including int , but not int[] .

Answer 2

You could deserialize the array using the ToObject<type> extension method (where type is the desired data type):

var jsonString = @"{ ""name"":""test"", ""array"": [""10"",""20"",""30"",""40""] }";
dynamic dynamicObject = JsonConvert.DeserializeObject(jsonString);
Console.WriteLine(((string)dynamicObject.name));
var items = dynamicObject.array.ToObject<int[]>();
foreach (var item in items)
{
    Console.WriteLine(item);
}

The output is:

test
10
20
30
40

Another possibility would be to cast the object to JObject and then fetch the array as a property - the retrieved object is automatically of type JToken , which allows iteration:

var array = ((JObject)dynamicObject)["array"];
foreach (var item in array)
{
    Console.WriteLine(item.ToString());
}