Pass multiple complex objects to Web API action

Working with ASP.NET Web API, the most unexpected thing is the limited support of POST data values to simple ApiController methods.

When a parameter has [FromBody], Web API uses the Content-Type header to select a formatter. At most one parameter is allowed to read from the message body. The reason for this rule is that the request body might be stored in a non-buffered stream that can only be read once.

A simple principle, you can send any content in HTTP request, it only need to be serializable into a string. So, it could be multiple JSON object. In this example, the content type is "application/json" and the request body is a raw JSON string (not a JSON object).

Here I found a workaround to pass multiple complex objects (using the above principle) from jquery to a WEB API using JObject, and then cast back to your required specific object type in api controller. This objects provides a concrete type specifically designed for working with JSON.

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var customer = { "Name": "jhon", "Id": 1, }; var product = { "Name": "table", "CategoryId": 5, "Count": 100 }; var employee = { "Name": "Fatih", "Id": 4, };   var combinedObj = {}; combinedObj["obj1"] = customer; combinedObj["obj2"] = product; combinedObj["obj3"] = employee;   $.ajax({ type: 'POST', async: true, url: 'api/PostGenericObjects/', data: JSON.stringify(combinedObj), success: function (response) { console.log("Response Data ↓"); console.log(response); }, error: function (err) { console.log(err); } });

and then you can get this object in your ApiController

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using Newtonsoft.Json.Linq;   public string PostGenericObjects(object obj) { string[] str = GeneralMethods.UnWrapObjects(obj); var customer = JsonConvert.DeserializeObject<Customer>(str[0]); var product = JsonConvert.DeserializeObject<Product>(str[1]); var employee = JsonConvert.DeserializeObject<Employee>(str[2]);   //... other work....   }

I have made a generic function to unwrap the complex object, so there is no limitation of number of objects while sending and unwrapping. We can even send more than two objects

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public class GeneralMethods {   public static string[] UnWrapObjects(object obj)   {     JObject o = JObject.Parse(obj.ToString());       string[] str = new string[o.Count];       for (int i = 0; i < o.Count; i++)     {       string var = "obj" + (i + 1).ToString();       str[i] = o[var].ToString();     }     return str;   } }

I hope it would help someone. I would be interested to hear from the experts here regarding the pros and cons of using this methodology. Do share your feedback.

Happy Coding!