Read-Only Structs: C# 7.2

C# supports two basic types : Value Type and Reference Type. The main difference between them where they get created: Value Types gets created in stack while Reference type in Heap. Other key difference, for ValueType whenever a parameter is passed as an argument, a copy gets created and passed while for reference types, refernce of the same onstance gets passed. There is another type called – Nullable Type but actually it’s a wrapper over value type. I wrote a post on it, you can have a look here.

All the Value Types internally inherits System.ValueType. Struct is also a ValueType which inherits same.

It’s a good idea to make struct immutable, it means once it is initalized, it cannot be modified. System.DateTime is an immutable Value Type. It provides many static methods but it always returns a new instance.

To make a struct immutable, the simple way to make all the members readonly and initializ these values via parameterized constructor. It’s members should be exposed via getter fields.

Let’s see an example

public struct Person
{
    public string FirstName { get; }

    public string LastName { get; }

    public int Age { get; }

    public Person(string firstName, string lastName, int age)
    {
        this.FirstName = firstName;
        this.LastName = lastName;
        this.Age = age;
    }
}

Above struct is immutable as there is no way to modify the initialized variable.

Read-Only structs:

Prior to C# 7.2, to create an Immutable value type, we had to write the struct in a way so that it doesn’t allow an update as in above example. If few fields are left without marking readonly/const unknowingly then it wont work as expected. C# 7.2 allows us to add readonly modifier before struct which makes sure thatg all the members are read only. If any member doesn’t, it will throw an error. Above struct can be marked as read only as

public readonly struct Person
{
    public string FirstName { get; }

    public string LastName { get; }

    public int Age { get; }

    public Person(string firstName, string lastName, int age)
    {
        this.FirstName = firstName;
        this.LastName = lastName;
        this.Age = age;
    }

}

One important thing, the parameterized constructor should be used to create the instance always else in case of using parameterless constructor use, the member would be set to default value which cannot be ever changed and we probably won’t want this. We cannot make parameter less private for struct in C# and even if there is a way we can bypass that. We can have some validate method which should be fired before using that struct’s memebers. I wont discuss this in details here.

Read-only struct provides framework support to write readonly struct and help us to avoid any unintended modification. In my previous post, I discussed about In modifier, it also can be used while passing any immutable object. These changes like ref, out, in etc in .NET framework got developed to make low level programming simpler and faster. Few more changes, we will be discussing in coming posts.

Note: If you are not sure how to use X# 7.2 (7.x) in your project, you may have a look on one of my previos post here.

Hope you enjoyed the post.

Cheers
Brij

Advertisements

Using In Parameter Modifier : C# 7.2

Changes are the only constant thing in the world and that got little faster with C# new releases as we have minor now releases (also referred as point releases) with significant enhancements. New features are getting added and existing features are getting enhanced. In one my earlier posts, I discussed about Ref and Out improvements that took places in C# 7.0. You can go through the link below.

Ref and Out improvements in C# 7.0

Let’s have a quick look on it

Here we can see that if we want to pass the argument by ref then reference of the instance (value type or reference type) is passed and any change the in the argument in the called method reflects in the calling method as well.

Note – If you are curious about the using the ref keyword with reference type object, you can have a look to one of my previous posts by clicking here.

Out parameters, are also like pass by reference except it enforces a rule that calling method pass the variable without initializing while called method must initialize.

Say you have a big struct or any other value type, that you have to pass as an argument. Everytime you will call the method, a new copy will be created and passed to the method. If this has to be done multiple times then it can be a major performance issue.

Also, out keyword  forces to the called method to initialize the variable but we dont have opposite option. And ref keyword allows to pass the paramter via reference and here caller and called method both can modify the variable.

C# 7.2 introduced another keyword In which provides the ability to pass the argument as readonly. It fails at compile time if there is any code which tries to modify in the called method. The variable must be initialized before passing as a parameter.

Lets see an example

There are few restrictions.

  1. In, Out and Ref keywords cannot be used in async methods.
  2. Cannot be used in iterator methods (which has yield statements)
  3. Marking the arguments of main method as In, makes it invalid as entry method.

To summarize, In keyword can be really useful when you are passing a big value type object to method which is called multiple times because instead of creating a new copy in each call, it will be passed by reference.

Cheers,
Brij

How to use C# 7.2 (7.x – minor releases) in your Project

C# 7.0 and other minor releases (7.x) are loaded with many awesome features and I’ve been all those nice features recently. You can have a look here. I have seen many people facing issues with using these features. So in this quick post, I will discuss how you can leverage C# 7.x features.

Using Visual Studio 2017

To use C# 7.x features, Microsoft recommends to upgrade the IDE to Visual Studio 2017. To use C# latest minor releases C# 7.X (currently C# 7.2), this is not enough, we need to follow the below steps

  1. Right click on the project => Select Properties
  2. Select Build tab from the left pane.
  3. Go down and select Advanced button
  4. Select the Language version as

Here we can see tha the default selection is C# latest major version (default) which means 7.0. We also have the option to select specific versions like 7.0/7.1 but for 7.2, we need to select C# latest minor version (latest).

Using Visual Studio 2015

As mentioned above that Microsoft recommends to use Visual Studio 2017 for C# 7.x features but as these features are implemented by compiler so as long as your build is pointing to correct version of CSC, you can build the new features. However, Visual Studio 2015 may not like it as it doesn’t understand the new features and you may not get intellisense or any other IDE support.

To use C# 7.X in Visual Studio 2015, install the following nuget package

Microsoft.Net.Compilers

Once, you install this package, you should be able to use the latest language feature in VS 2015. However you might red   squiggly in the editor as

Here we can see that even the VS2015 editor is complaining but it is getting built.

Using System.ValueTuple

ValueTuple is not available by default as part of C# 7.0, we need to install following nuget package

System.ValueTuple

Hope you like the post and able to use the C# latest features.

Cheers,
Brij