NullObjectReference when performing a PUT in Web Api - asp.net-web-api2

Question

I am trying to update a variable inside a class "Conversation" put the parameter objects are not binding for some reason. I don't know why not. As a result I am getting this error:
"Object reference not set to an instance of an object.",
Controller:
[HttpPut]
public async Task<IHttpActionResult> AddMember(string key, User user)
{
if (!ModelState.IsValid)
{
return BadRequest(ModelState);
}
Conversation conver = await db.Conversations.FindAsync(key); //THIS IS NULL
if (conver == null)
{
return NotFound(); //METHOD IS ENDING HERE
}
conver.Members.Add(user); //THIS IS NULL
db.Entry(conver).State = EntityState.Modified;
try
{
await db.SaveChangesAsync();
}
catch (DbUpdateConcurrencyException)
{
return NotFound();
}
return StatusCode(HttpStatusCode.NoContent);
}
Model class User:
namespace AcademicAssistant.Models
{
[DataContract]
public class User
{
[Key]
[DataMember]
public string Email { get; set; }
[DataMember]
public string Password { get; set; }
[DataMember]
public bool Admin { get; set; }
}
}
Model Class Conversation:
[DataContract]
public class Conversation
{
[Key]
[DataMember]
public string Key { get; set; }
[DataMember]
public string ConversationName { get; set; }
[DataMember]
public string Administrator { get; set; }
[DataMember]
public virtual ICollection<User> Members { get; set; }
[DataMember]
public virtual ICollection<Message> Messages { get; set; }
}
I am testing this in Postman like this:
ROUTE = api/Conversations/AddMember/?key="1LM4"
JSON = {"user": { "Email": "56#56.com", "Password" : "Passw-1", "Admin" : true } }

Answer 1

SOLUTION:
The Route should have been
api/Conversations/AddMember/?key=1LM4
and the JSON formatted like this:
{
"Email": "56#56.com",
"Password" : "Passw-1",
"Admin" : true
}