How to support multiple names for a property using System.Text.Json Deserialization?

Question

Hello together,

right now I'm reading following learn article:

https://learn.microsoft.com/en-us/dotnet/standard/serialization/system-text-json/custom-contracts

It is written

Support multiple names for a single property (for example, if a previous library version used a different name).

Since JsonPropertyNameAttribute is only allowed once, does this mean only 2 names are possible like that?

public class Test {
    [JsonPropertyName("Value2")]
    public string Value1 { get; set; };
}

How could I handle deserializiing two json objects, differing only in the name of the Value, into my class?

public class Test {
    [JsonPropertyName("Value2")]
    [JsonPropertyName("Value1")]
    public string Value { get; set; }

    public string Desc { get; set}
}

I dont want to inherit from the Test class and override those propertys to have each a JsonPropertyNameAttribute assigned to.

Best regards

Answer 1

@PFJ, Welcome to Microsoft Q&A, you could try to add a second property to your class.

Here is a code example you could refer to.

   internal class Program
    {
        static void Main(string[] args)
        {
            string json1 = @"{""Value1"":""test1"",""Desc"":""This is d1""}";
            string json2 = @"{""Value2"":""test2"",""Desc"":""This is d2""}";

            var obj1 = JsonSerializer.Deserialize<Test>(json1); 
            var obj2= JsonSerializer.Deserialize<Test>(json2);
            Console.WriteLine(obj1.Value1);
            Console.WriteLine(obj2.Value1);

        }
    }
    public class Test
    {
       
        [JsonPropertyName("Value1")]
        public string Value1 { get; set; }

        [JsonPropertyName("Value2")]
        public string Value2 { set { Value1 = value; } }

        public string Desc { get; set; }
    }

As the result is shown, we also could output the Value2's value:

Hope my solution could be helpful for you.

Best Regards,

Jack

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Answer 2

Only one attribute is allowed. But with a custom contract you could write code that determines the property name. One of the use cases is multiple names for a single property.