Create a JSON string in C#

{
    "Name" : "22", 
    "Age" : "0", 
    "FullAddress" : "-5", 
    "Interest" : "0"
}

to create a json string as shown below, here is what you could use.

string myJsonString =   "{"
                        + "\"Name\": \"" + model.FirstName + "\", "
                        + "\"Age\": \"" + model.Age + "\", "
                        + "\"Address\": \"" + model.FullAddress + "\", "
                        + "\"Interests\": \"" + model.Interests +"\" "
                        + "}";