Setting value of attribute in serviceContext when using JSON WS of Liferay

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C#

C#4.0

Hi,

I am accessing liferay services in C#.NET. I need to setup attributes field of serviceContext parameter when calling a service e.g. /dlapp/update-file-entry
I am able to set workflow action using the below format:

formData.Add(new StringContent(status + ""), "serviceContext.workflowAction");

but don't know how to set value of an attribute e.g. setting fileEntryTypeId for a txt file to RichText

I've tried below format, but it is not working

formData.Add(new StringContent("211990"), "serviceContext.attributes.fileEntryTypeId");

kindly provide any pointers, help in this regard

Thanks