Using JSON.Net how can I serialize a dynamic and force all string values to lower case?

Question

In an object I am serializing to a document database I have a dynamic property that needs all string values written in lower-case for indexing purposes. I tried using a custom converter for this, but that requires me to write serialization code for several different types. All I want is the standard serialization behavior, but with the string values forced to lower-case. Given the flexibility of the Newtonsoft library this seems like it should be straightforward, I just haven't found the right interface.

Note that I don't have direct control over serialization. I am writing to Azure COSMOSDB, and their client library uses JSON.Net for serialization. I am able to pass in a custom serializer to use.

Update

The following appears to work. Steps are:

add code to populate the dynamic property via JToken.FromObject()
use code below to force all string values to lower-case (arrays were tricky)

send object to CosmosDB

private static JToken JTokenStringValuesToLower(JToken startToken)
{
    Stack<JEnumerable<JToken>> tokenStack = new Stack<JEnumerable<JToken>>();
    tokenStack.Push(startToken.Children());

    while (tokenStack.Count != 0)
    {
        JEnumerable<JToken> children = tokenStack.Pop();

        foreach (JToken child in children)
        {
            if (child.Type == JTokenType.Property)
            {
                JProperty property = (JProperty)child;

                if (child.HasValues)
                {
                    tokenStack.Push(child.Children());
                }

                if (property.Value.Type == JTokenType.String)
                {
                    property.Value = property.Value.ToString().ToLowerInvariant();
                }
            }
            else if (child.Type == JTokenType.Array && child.HasValues)
            {
                JArray array = (JArray)child;
                JToken[] arrayItems = new JToken[array.Count];
                int idx = 0;
                bool modified = false;

                foreach (JToken arrayItem in array.Children())
                {
                    arrayItems[idx++] = arrayItem;
                }

                for (int i = 0; i < arrayItems.Length; ++i)
                {
                    JToken token = arrayItems[i];

                    if (token.Type == JTokenType.String)
                    {
                        modified = true;
                        arrayItems[i] = token.ToString().ToLowerInvariant();
                    }
                }

                if (modified)
                {
                    array.Clear();

                    foreach (JToken item in arrayItems)
                    {
                        array.Add(item);
                    }
                }
            }
            else if (child.HasValues)
            {
                tokenStack.Push(child.Children());
            }
        }
    }

    return startToken;
}

Since it's the values that you want forced to lowercase I don't think this is a job for JSON.net or any Json serialiser. Can't you simply pass all of the values through a conversion function before saving to CosmosDB? Or if you know they're all strings can't you just say someDynamicObject.someProperty.ToString().ToLower() on each of the fields? — Dan
– Dan, Commented Aug 25, 2017 at 17:34

devio · Accepted Answer · 2017-08-25 17:20:41Z

0

For a similar question, I found the use of JToken very powerful, as this example (SO) shows how to iterate through a JSON data structure and manipulate each data node based on type or content.

answered Aug 25, 2017 at 17:20

devio

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1 Comment

Peter Friend Over a year ago

I think this would work if I had control over serialization. I edited my question to note that I am using Azure CosmosDB, and their client library handles serialization. I can pass in a serializer, but not the serialized string.

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