When <Tvalue> contains null fields, why does PostAsJsonAsync fail to call the Controller?

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PostAsJsonAsync method fails to call the controller when <tvalue> contains null fields because it sends the serialized data as JSON to the server, and JSON does not support null values. When the server receives the JSON data with null values, it tries to deserialize it, but it fails because JSON does not provide any way to differentiate between a null value and a missing value. Therefore, the server cannot map the incoming JSON data to the model object, and it returns an error. To resolve this issue, you need to either set default values for the null fields or use a different serialization format that supports null values.