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C# C# Streams and Data Processing Serialization Using Json.NET

Ranvir Sahota
Ranvir Sahota
9,844 Points
Posted by Ranvir Sahota
Ranvir Sahota
9,844 Points

why use Deserilize<T>(JsonReader)

In the video, the teacher says don't want to use Deserilize method that returns an object because she would have to cast it. So what are the differences between t and object their advantages and disadvantages? What were her reasons for not casting? I've been reading into boxing and unboxing and in general about t, but I feel like im missing something an explanation about this I believe will clear up my misunderstanding. Thank you.

5 Answers

James Churchill
STAFF
James Churchill
Treehouse Teacher
James Churchill
James Churchill
Treehouse Teacher

Ranvir,

One of the advantages of open source software is that we can go read the source code to see what the differences are between two different methods. Here's a link to the implementation of the generic Deserialize<T> method:

https://github.com/JamesNK/Newtonsoft.Json/blob/master/Src/Newtonsoft.Json/JsonSerializer.cs#L844

And here's the method implementation:

public T Deserialize<T>(JsonReader reader)
{
    return (T)Deserialize(reader, typeof(T));
}

In this code snippet, we can see that the method delegates to the non-generic Deserialize method and simply casts the object returned from that method to type of T. Here's the implementation of the non-generic Deserialize method:

public object Deserialize(JsonReader reader, Type objectType)
{
    return DeserializeInternal(reader, objectType);
}

That method itself delegates to an internal method named DeserializeInternal. Here's the link to that method in the source code:

https://github.com/JamesNK/Newtonsoft.Json/blob/master/Src/Newtonsoft.Json/JsonSerializer.cs#L861

So, as Steven speculated above, the generic Deserialize method is really just a convenience method that saves you from having to do the cast yourself.

I hope this helps! Please let me know if you have any further questions.

Thanks ~James

Adham Ali
Adham Ali
Courses Plus Student 1,112 Points

Well in Deserialize<T> it seems that doesn`t solve any performance issues it casts the return type to a <T> which we would do actually if we use the non-generic Deserialize method. The unboxing impact is still there

James Churchill
James Churchill
Treehouse Teacher
James Churchill
James Churchill
Treehouse Teacher

Adham,

Explicitly casting an object to another reference type (presumably a custom type defined by a class)--which is what is happening in the generic Deserialize<T> method--is not the same thing as boxing/unboxing. Boxing is the act of converting a value type to an object. Before we had the System.Collections.Generic namespace (introduced in .NET 2.0), this was a common performance issue developers had to deal with, as the available collections in the System.Collections namespace only worked with objects (see ArrayList https://msdn.microsoft.com/en-us/library/system.collections.arraylist(v=vs.110).aspx for an example).

For more information about boxing and unboxing, see: https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/types/boxing-and-unboxing

Thanks ~James

Steven Parker
Steven Parker
231,198 Points
Steven Parker
Steven Parker
231,198 Points

I would not expect a functional difference, but it seems that using the generic is cleaner looking and a more modern technique. If you want a more definitive answer you could try tagging Carling and see if she responds.

Adham Ali
PLUS
Adham Ali
Courses Plus Student 1,112 Points
Adham Ali
Adham Ali
Courses Plus Student 1,112 Points

to avoid boxing and unboxing. If you wanna understand this in depth(actually you gotta because you are a software developer)you should see both of this articles (in order):

1-An Introduction to C# Generics - MSDN - Microsoft:

This is an Introduction to gerneric types in C#

2-Generics (C# Programming Guide) | Microsoft Docs:

This is an Generic types in more depth in C#

Adham Ali
PLUS
Adham Ali
Courses Plus Student 1,112 Points
Adham Ali
Adham Ali
Courses Plus Student 1,112 Points

Mr. James,

I mean that non-generic Deserialize method returns an object right? The generic one casts the object returned from non-generic Deserialize to the Type parameter specified between the angle brackets. the unboxing impact still there. That's what I`m trying to say. Thanks

James Churchill
James Churchill
Treehouse Teacher
James Churchill
James Churchill
Treehouse Teacher

Adham,

Assuming that type T in Deserialize<T> is a reference type (and not a value type), then there isn't any boxing or unboxing occurring. Boxing only occurs when converting a value type to a type object (or to any interface type implemented by the value type).

Thanks ~James

Adham Ali
PLUS
Adham Ali
Courses Plus Student 1,112 Points
Adham Ali
Adham Ali
Courses Plus Student 1,112 Points

Mr. James, Yeah yeah i got what u tryna mean ! Thanks, sir

Can i ask you a question? later in this course i couldn't do the bing subscriptions keys thing could u explain to me how to do it Keep in mind that the video is from 2015 or 2016 i dont know exactly and the design of the site is changed

Thanks!