Json.NET DeserializeObject allow constructor exception to bubble up

Question

I am using the JsonConvert.DeserializeObject<T>(string value) method to deserialize an object of type T from a string.

In a custom class (which I am attempting to deserialize) I perform checks on the arguments supplied to the constructor and can throw an ArgumentNullException. However, this exception does not bubble up through the deserializer and to the original caller, and therefore the exception stays unhandled inside the constructor.

This is the generic method I am using in a helper class:

public static T FromJsonString<T>(string json)
{
    try
    {
        return JsonConvert.DeserializeObject<T>(json);
    }
    catch(ArgumentNullException)
    {
        // Would like to handle exception here, but never reached
    }
}

My class constructor example:

[JsonConstructor]
public Profile(string name, ...)
{
    if (string.IsNullOrWhiteSpace(name)) { throw new ArgumentNullException("name"); }
    // ...
}

I have attempted using JsonSerializerSettings when calling DeserializeObject<T>(), for example the Error property, however this made no difference.

How can I make the exception bubble up and not stay inside the constructor of my class?

Answer 1

The problem is caused by Visual Studio breaking on the exception as it is classed as "user-unhandled". In Debug > Windows > Exception Settings you can change which exceptions break and which do not.