New in .NET 8.0 (28): Extensions for deserialization of JSON objects

with the newly introduced function UnmappedMemberHandling It’s about how System.Text.Json The behavior occurs when the object has more properties than the properties when deserializing.

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In the example code below, this JSON string has a property “CITY” but no corresponding property exists City in class Consultant and its base class Person,

Classes Consultant And Person was already used in the previous section and is not reproduced here. Discontinuation of the naming convention was also discussed.

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try
{
 var jsonString = """
 {
 "ID":42,
 "FULL-NAME":"Holger Schwichtenberg",
 "PERSONAL-WEBSITE":"www.dotnet-doktor.de",
 "CITY":"Essen"
 }
 """;
 Console.WriteLine("JSON: " + jsonString);
 var obj = JsonSerializer.Deserialize(jsonString, options);
 if (obj != null) CUI.Success(obj.ToString());
}
catch (Exception ex)
{
 CUI.PrintError(ex.Message); 
}

would have happened till now System.Text.Json The extra information is easily overlooked. This is still the case in the standard edition. Through annotations (JsonUnmappedMemberHandling) on the class or property to be deserialized UnmappedMemberHandling in object JsonSerializerOptions Developers can now change this: The allowed values ​​are Skip (ignore as before) and Disallow,

The following shot of Disallow So the above solves it Deserialize() A runtime error: “The JSON property ‘CITY’ could not be mapped to any .NET member contained in the type ‘FCL_JSON.Consultant’.”

var options = new JsonSerializerOptions
{
 // NEU: Enumeration JsonNamingPolicy mit Namenskonventionen 
 // KebabCaseLower, KebabCaseUpper, SnakeCaseLower 
 // und SnakeCaseUppter als Alternative zum 
 // bisher fest gesetzten CamelCase
 PropertyNamingPolicy = JsonNamingPolicy.KebabCaseUpper, 
 // Standard wäre CamelCase
 
 // NEU: Einstellungen zur Handhabung zusätzlicher Daten
 // bei der Deserialisierung von JSON in Objekten 
 // via Annotation (JsonUnmappedMemberHandling) 
 // oder Eigenschaft UnmappedMemberHandling 
 // im Objekt JsonSerializerOptions.
 UnmappedMemberHandling = JsonUnmappedMemberHandling.Disallow, 
 // Default wäre Skip
};

(RME)