如何使用“动态”变量从匿名类型中读取属性

Question

I had the cunning idea of using a dynamic variable to test the results of a method that returns an anonymous type - more specifically it returns a JsonResult, which as json looks like this

{ "newData" : [ 1120741.2697475906,
      826527.64681837813
    ],
  "oldData" : [ 1849870.2326665826,
      1763440.5884212805
    ],
  "timeSteps" : [ 0,
      4.8828124999999998e-10
    ],
  "total" : 2
}

I can read the JSonResult which will give me the anonymous type. Here's my code:

var jsonResult = controller.GetChangeData(1) as JsonResult;
dynamic data = jsonResult.Data;
Assert.AreEqual(2, data.total); // This works fine :)

But how do I get at "newData" for example? This code....

var newData = data.newData;

Gives me a System.Linq.Enumerable.WhereSelectArrayIterator, but I don't know what to do with it to be able to just use it as an arry of doubles.

I tried casting it as a double[], but it doesn't work either.

As an aside, can I easily check if a property is defined on the dynamic?

Answer 1

The reason .ToArray() doesn't work is that it's an extension method, and extension methods aren't available at runtime. That just means you have to call the function statically. Does Enumerable.ToArray<double>(data.newData) work?

You may need Enumerable.ToArray(Enumerable.Cast<double>(data.newData)) depending on what elements newData actually has.

Answer 2

To get the properties of an instance of a dynamic type

PropertyDescriptorCollection props = TypeDescriptor.GetProperties(dyn);
foreach (PropertyDescriptor prop in props)
{
  object val = prop.GetValue(dyn);
  var propName = prop.Name;
  var propValue = val;
}

where dyn is an instance of a dynamic object.

Answer 3

Could you use the JavaScriptSerializer class to parse the Json string into a dynamic variable? Eg:

var serializer = new JavaScriptSerializer();
var jsonObj = serializer.Deserialize<dynamic>(jsonString);
var newData1 = jsonObj["newData"][0];