ReadAsAsync got null values from Json data?

Question

I have a class

public class C
{
    public int Id { get; set; }
    public SqlXml Range { get; set; } // System.Data.SqlTypes.SqlXml
}

And the following code is used to read the data from web api.

    List<C> cs = null;
    var response = await client.GetAsync(url);
    if (response.IsSuccessStatusCode)
    {
        cs = await response.Content.ReadAsAsync<List<C>>(); // cs[..].Range is null
    }

The following is some sample Json file returned from the Web API.

[{"id":0,"range":{"isNull":false,"value":"<Range>....</Range>"}},
 {"id":1,"range":{"isNull":false,"value":"<Range>...</Range>"}},
 {"id":2,"range":{"isNull":false,"value":"<Range>....</Range>"}}]

However, the variable cs got the following values. The Id values are correct. But all the Ranges got null values?

0, null
1, null
2, null

The debugger shows cs[...].Range.IsNull is true.

Can you show definition of SqlXml class. maybe json.net is unable to desrialize that object, but will need to see what it looks like. — Nkosi
– Nkosi, Commented Feb 28, 2018 at 1:24

Nkosi · Accepted Answer · 2018-02-28 01:37:41Z

2

The properties of System.Data.SqlTypes.SqlXml are read only. When the deserializer tries to create objects of that type it will fail while trying to set the properties.

Create you own class to hold the desired values

public class Range {
    public bool IsNull { get; set; }
    public string Value { get; set; }
}

public class C {
    public int Id { get; set; }
    public Range Range { get; set; }
}

This should now allow the Range values to be properly populated

answered Feb 28, 2018 at 1:37

Nkosi

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