根据查询字符串返回对象

Question

I'm trying to return objects based on query strings.
For example, I would like api/users/{id}?fields=username,email,reputation to return an object of type User that contains only the three included properties (username, email, reputation).

On a side note, comma separated query strings are not possible by default in .NET Core.
Here's a tutorial on making that work .

Following the guide above, I have a list of strings. How can I create an object that only includes the properties that match the names of those strings?
For only a few strings I can do this (thanks Ben Hall):

List<string> listOfStrings ...; // Strings from query
User user = GetUser(id); // User from db 

User newUser = new User();

if (listOfStrings.Contains("username"))
    newUser.username = user.username;
if (listOfStrings.Contains("email"))
    newUser.email = user.email;
if (listOfStrings.Contains("reputation"))
    newUser.reputation = user.reputation;

But for a long list of strings (my user class has 30+ properties) how would I go about doing this?

For reference, Facebook Graph API does this.

Answer 1

List<string> listOfStrings ...; // Strings from query
User user = GetUser(id); // User from db 

User newUser = new User();
//gettting object type
var userType = user.GetType();

This solution needs some knowledge about Reflections
It uses the methods GetValue and SetValue
(The code is tested in Visual Studio)
Now foreach element in listOfStrings

foreach(var propertyName in listOfString){
// This line of code retrives the value of the propety in the user class
 var retrivedValue = userType.GetProperty(propertyName).GetValue(user);
// This line of code sets the value retrived to the property in the newUser class
 userType.GetProperty(propertyName).SetValue(newUser, retrivedValue , null);
}

Answer 2

We could explore other ways like reflection but if should still serve you well enough. Looks like you're making a simple mistake trying to use an If in an object initialiser. You will have to do that after instaniating the new User object eg

User newUser = new User();
if (listOfStrings.Contains("username"))
{
       newUser.username = user.username;
}

Answer 3

Turns out there is actually Middleware for this called Popcorn.

Popcorn is a communication protocol on top of a RESTful API that allows requesting clients to identify individual fields of resources to include when retrieving the resource or resource collection.

It allows for a recursive selection of fields, allowing multiple calls to be condensed into one.

Features:

• Selective inclusion from a RESTful API
• Configurable response defaults
• Sorting of responses
• Selective authorization and permissioning of response values
• Configurable response inspectors
• Factory and advanced projection support
• Set relevant contexts for your API
• Blind expansion f response objects