Databases
StackOverflow2013
Postsdbo
POSerializing null in JSON.NET
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POSerializing null in JSON.NET
    primarykey
    data
    text
    <p>When serializing arbitrary data via JSON.NET, any property that is null is written to the JSON as </p> <blockquote> <p>"propertyName" : null</p> </blockquote> <p>This is correct, of course. </p> <p>However I have a requirement to automatically translate all nulls into the default empty value, e.g. null <code>string</code>s should become <code>String.Empty</code>, null <code>int?</code>s should become <code>0</code>, null <code>bool?</code>s should be <code>false</code>, and so on. </p> <p><code>NullValueHandling</code> is not helpful, since I dont want to <code>Ignore</code> nulls, but neither do I want to <code>Include</code> them (Hmm, new feature?). </p> <p>So I turned to implementing a custom <code>JsonConverter</code>.<br> While the implementation itself was a breeze, unfortunately this still didnt work - <code>CanConvert()</code> is never called for a property that has a null value, and therefore <code>WriteJson()</code> is not called either. Apparently nulls are automatically serialized directly into <code>null</code>, without the custom pipeline. </p> <p>For example, here is a sample of a custom converter for null strings:</p> <pre><code>public class StringConverter : JsonConverter { public override bool CanConvert(Type objectType) { return typeof(string).IsAssignableFrom(objectType); } ... public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer) { string strValue = value as string; if (strValue == null) { writer.WriteValue(String.Empty); } else { writer.WriteValue(strValue); } } } </code></pre> <p>Stepping through this in the debugger, I noted that neither of these methods are called for properties that have a null value.</p> <p>Delving into JSON.NET's sourcecode, I found that (apparently, I didnt go into a lot of depth) there is a special case checking for nulls, and explictly calling <code>.WriteNull()</code>.</p> <p>For what it's worth, I did try implementing a custom <code>JsonTextWriter</code> and overriding the default <code>.WriteNull()</code> implementation... </p> <pre><code>public class NullJsonWriter : JsonTextWriter { ... public override void WriteNull() { this.WriteValue(String.Empty); } } </code></pre> <p>However, this can't work well, since the <code>WriteNull()</code> method knows nothing about the underlying datatype. So sure, I can output <code>""</code> for any null, but that doesnt work well for e.g. int, bool, etc. </p> <p>So, my question - short of converting the entire data structure manually, is there any solution or workaround for this? </p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USAviD
    1. USAviD
    plurals
    1. This table or related slice is empty.
    1. PL
      singulars
      1. LTLinked
    2. PL
      singulars
      1. LTLinked
    3. PL
      singulars
      1. LTLinked
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POSerializing null in JSON.NET
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POSerializing null in JSON.NET
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. POSerializing null in JSON.NET
      1. This table or related slice is empty.
      1. VTUpMod
    1. COI'm guessing the `WriteNull()` method is called internally within the JSON serialization process and you can't determine which value you are currently serializing?
      singulars
      1. POSerializing null in JSON.NET
      1. USSamuel Slade
    2. COThe WriteNull method is called by the JsonSerializer when the property has a null value. To be accurate, the value I'm serializing is always null :), but yes there seems to be no way to know the underlying data type for which the null is being written.
      singulars
      1. POSerializing null in JSON.NET
      1. USAviD
    3. COWhat's the point of using nullable types if you are just going to ignore null as a valid state of the object?
      singulars
      1. POSerializing null in JSON.NET
      1. USJames Holmes
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload