What's the best practice for retrieving JSON values that may not even exist in C# using Json.NET?
Right now I'm dealing with a JSON provider that returns JSON that sometimes contains certain key/value pairs, and sometimes does not. I've been using (perhaps incorrectly) this method to get my values (example for getting a double):
if(null != jToken["width"])
width = double.Parse(jToken["width"].ToString());
else
width = 100;
Now that works fine, but when there are a lot of them it's cumbersome. I ended up writing an extension method, and only after writing it did I wonder whether maybe I was being stupid... anyways, here is the extension method (I only include cases for double and string, but in reality I have quite a few more):
public static T GetValue<T>(this JToken jToken, string key,
T defaultValue = default(T))
{
T returnValue = defaultValue;
if (jToken[key] != null)
{
object data = null;
string sData = jToken[key].ToString();
Type type = typeof(T);
if (type is double)
data = double.Parse(sData);
else if (type is string)
data = sData;
if (null == data && type.IsValueType)
throw new ArgumentException("Cannot parse type "" +
type.FullName + "" from value "" + sData + """);
returnValue = (T)Convert.ChangeType(data,
type, CultureInfo.InvariantCulture);
}
return returnValue;
}
And here's an example of using the extension method:
width = jToken.GetValue<double>("width", 100);
BTW, Please forgive what may be a really dumb question, since it seems like something there should be a built in function for... I did try Google, and Json.NET documentation, however I'm either inept at finding the solution to my question or it's not clear in the documentation.
See Question&Answers more detail:
os 与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…