Handling possible null value when converting JSON to C# class

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Category:Languages

I've run into an interesting problem when converting API data to a C# class in UWP.

I have an API that returns image dimensions, like this:

{     "height": "25",     "width": "25" } 

I also have a class with properties that match the JSON data, generated by json2csharp.com.

public class Image {     public int height { get; set; }     public Uri url { get; set; }     public int width { get; set; } } 

And I am converting the JSON to a C# class using something like this:

dynamic JsonData = JObject.Parse(JsonString); Image img = JsonData.ToObject<Image>(); 

However, if the API does not know the height or width, it returns null instead of an int, like this:

{     "height": null,     "width": "25" } 

This obviously causes an exception to throw, specifically this error message:

Newtonsoft.Json.JsonSerializationException: Error converting value {null} to type 'System.Int32'

Is there some way to work around this or handle this scenario?

 


You can make an int nullable by adding a ?:

public class Image {     public int? height { get; set; }     public Uri url { get; set; }     public int? width { get; set; } } 

Other than json2csharp.com, QuickType can also help you do this:

public partial class Image {     [JsonProperty("height")]     [JsonConverter(typeof(ParseStringConverter))]     public long? Height { get; set; }      [JsonProperty("width")]     [JsonConverter(typeof(ParseStringConverter))]     public long Width { get; set; } } 

You have to add in the URL property yourself. QuickType also generates a bunch of other things for you as well, such as the ParseStringConverter custom JsonConverter.

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