C#- deserialize json to object

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Hi..I have an issue with json serialization which throws the error: 

"Could not cast or convert from System.String to System.Collections.Generic.IList`1[System.String].]".
 
My json: "{\"Type\": \"abc\",\"Filepath\": \"D:\\\\abc.doc\"}"; 
My class: 
public class Arguments { public string Type { get; set; } 
public IList Filepath { get; set; } } 
My code to deserialize: 
var jsonObj = new JavaScriptSerializer().Deserialize(json); 

Can you help me understand the issue? I have made it a list as there can be situation to receive multiple objects and hence it is required. Would be great if you can help me!

It works fine when i have multiple values, ie:
 "{\"Type\": \"abc\",\"Filepath\": [\"D:\\\\abc1.doc\",\"D:\\\\abc2.doc\"]}";
I want it to work fine in both ways.

What I have tried:

My code to deserialize: 
var jsonObj = new JavaScriptSerializer().Deserialize(json);

Posted 5-Mar-19 3:03am

Member 7677029

Updated 5-Mar-19 3:24am

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2 solutions

Solution 2

That's a terrible JSON schema. You'll have to use JSON.NET[^] with a custom converter to read it.

This StackOverflow thread[^] has an example:

C#

class SingleOrArrayConverter<T> : JsonConverter
{
    public override bool CanConvert(Type objectType)
    {
        return (objectType == typeof(List<T>));
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        JToken token = JToken.Load(reader);
        if (token.Type == JTokenType.Array)
        {
            return token.ToObject<List<T>>();
        }
        return new List<T> { token.ToObject<T>() };
    }

    public override bool CanWrite
    {
        get { return false; }
    }

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        List<T> list = (List<T>)value;
        if (list.Count == 1)
        {
            value = list[0];
        }
        serializer.Serialize(writer, value);
    }
}

...

[JsonConverter(typeof(SingleOrArrayConverter<string>))]
public List<string> Filepath { get; set; }

Posted 5-Mar-19 3:25am

Richard Deeming

Updated 5-Mar-19 3:27am

v2

Comments

Member 7677029 5-Mar-19 9:27am

Thanks for the response, however i cannot use json.net :(

Richard Deeming 5-Mar-19 9:29am

The you'll have to get the person who's generating the JSON to fix their schema so that it always sends an array. The JavaScriptSerializer class can't cope with a property being either an array or a single value.

Graeme_Grant 5-Mar-19 13:14pm

5'd

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Graeme_Grant · Accepted Answer · 2019-03-05T03:23:00

Okay, this

{
    "Type": "abc",
    "Filepath": "D:\\abc.doc"
}

deserializes to this:

C#

public class Example
{
    public string Type { get; set; }
    public string Filepath { get; set; }
}

And this

{
    "Type": "abc",
    "Filepath": ["D:\\abc1.doc","D:\\abc2.doc"]
}

deserializes to this:

C#

public class Example
{
    public string Type { get; set; }
    public IList<string> Filepath { get; set; }
}

So the error that you are seeing:

"Could not cast or convert from System.String to System.Collections.Generic.IList`1[System.String].]".

Should now have more meaning. So you can not deserialize this:

{
    "Type": "abc",
    "Filepath": "D:\\abc.doc"
}

to this:

C#

public class Example
{
    public string Type { get; set; }
    public IList<string> Filepath { get; set; }
}

For more information on working with deserializing JSON, check out this article: Working with JSON in C# & VB[^]