JSON.NET Line serialization winrt

问题

I'm having some trouble with serializing a ObservableCollection of Lines (Shape). I'm developing for Windows RT and I'm using JSON.NET v5.02. I'm getting the following exception for the code below:

ObservableCollection<Line> lines;
//some code
string linesString = JsonConvert.SerializeObjectAsync(lines); // problem

An exception of type Newtonsoft.Json.JsonSerializationException occurred in mscorlib.dll but was not handled in user code

Additional information: Error getting value from 'X1' on 'Windows.UI.Xaml.Shapes.Line'.

If there is a handler for this exception, the program may be safely continued.

Is this a bug and is there a possible workaround?

回答1:

Your problem is a cross thread problem. When using await JsonConvert.SerializeObjectAsync(lines); that function will be executed in another thread (not the UI thread). Since a Windows.UI.Xaml.Shapes.Line is a UIElement and was created in the UI (main) thread you can't access the properties of the object in another thread. The solution would be to convert it to a simpler object that doesn't have this restrictions.

Besides, a Windows.UI.Xaml.Shapes.Line contains a lot of information, Visibility, IsEnabled etc, I think you would only need the X1, X2, Y1 and Y2. So you could just use this:

string s = await JsonConvert.SerializeObjectAsync(lines
             .Select(l => new 
                     {
                         l.X1,
                         l.X2,
                         l.Y1,
                         l.Y2
                     }).ToArray());

In this way, you get the properties you need in your UI (main) thread. Then pass that array to the serialize function. This way it works.

string s would now contain:

[{"X1":20.0,"X2":20.0,"Y1":40.0,"Y2":40.0},{"X1":20.0,"X2":20.0,"Y1":40.0,"Y2":40.0},{"X1":20.0,"X2":20.0,"Y1":40.0,"Y2":40.0},{"X1":20.0,"X2":20.0,"Y1":40.0,"Y2":40.0}]

回答2:

I am not sure whether Json.Net allow serializing framework class object. I tried with this.

public class CustomLine
{
    public double X1 { get; set; }
    public double X2 { get; set; }
    public double Y1 { get; set; }
    public double Y2 { get; set; }
}

I Changed the Line to CustomLine line. If you want to use Line class then retrieve properties X1, X2, Y1, Y2 and then assign it to CustomLine class properties.

来源：https://stackoverflow.com/questions/15944553/json-net-line-serialization-winrt

标签

serialization

windows-8

line

json.net

observablecollection