What should be the class structure for this Json?

See more:

C#

C#4.0

JSON

MVC4

I try to parse this below json string in class object

The Json String is:

{"formula":"MaxDate","parameters":[{"Value":"03/25/2014","Type":"Date"},{"Value":"22","Type":"Unit"}]}

And the class i create is:

class CustomFormula
{
    public string formula { get; set; }
    public List<Parameters> parameters { get; set; }
}
public class Parameters
{
    public string Value { get; set; }
    public string Type { get; set; }
}

To parse the code is:

JavaScriptSerializer JsonSerializer = new JavaScriptSerializer();
CustomFormula OCustomFormula =(CustomFormula)JsonSerializer.DeserializeObject(formulaValue.ToString());

But I am Getting the exception :

"Unable to cast object of type 'System.Collections.Generic.Dictionary`2[System.String,System.Object]' to type 'WDCS.MODELS.CustomFormula'."

Please help ?