New features in C# 6.0

28 Oct

This post covers what are the new language features in C# 6.0. Also a new compiler has been introduced code name “Roslyn”. The compiler source code is  open source and can be downloaded at codeplex site from the following link https://roslyn.codeplex.com/.

New features in C# 6.0

We can discuss about each of the new feature but first list of few features in C# 6.0

  1. Auto Property Initializer
  2. Primary Consturctors
  3. Dictionary Initializer
  4. Declaration Expressions
  5. Static Using
  6. await inside catch block
  7. Exception Filters
  8. Conditional Access Operator to check NULL Values

1. Auto Property initialzier


 Before

The only way to initialize an Auto Property is to implement an explicit constructor and set property values inside it.

public class AutoPropertyBeforeCsharp6
{
    private string _postTitle = string.Empty;
    public AutoPropertyBeforeCsharp6()
    {
        //assign initial values
        PostID = 1;
        PostName = "Post 1";
    }

    public long PostID { get; set; }

    public string PostName { get; set; }

    public string PostTitle
    {
        get { return _postTitle; }
        protected set
        {
            _postTitle = value;
        }
    }
}

After

In C# 6 auto implemented property with initial value can be initialized with out having to write the constructor. We can simplify the above example to the following

public class AutoPropertyInCsharp6
{
    public long PostID { get;  } = 1;

    public string PostName { get; } = "Post 1";

    public string PostTitle { get; protected set; } = string.Empty;
}

 2. Primary Constructors


We mainly use constructor to initialize the values inside it.(Accept parameter values and assign those parameters to instance properties).

Before

public class PrimaryConstructorsBeforeCSharp6
{
    public PrimaryConstructorsBeforeCSharp6(long postId, string postName, string postTitle)
    {
        PostID = postId;
        PostName = postName;
        PostTitle = postTitle; 
    }

    public long PostID { get; set; }
    public string PostName { get; set; }
    public string PostTitle { get; set; }
}

After

public class PrimaryConstructorsInCSharp6(long postId, string postName, string postTitle)
{        
    public long PostID { get;  } = postId;
    public string PostName { get; } = postName;
    public string PostTitle { get;  } = postTitle;
}

In C# 6,  primary constructor gives us a shortcut syntax for defining constructor with parameters. Only one primary constructor per class is allowed.

If you closely at the above example we moved the parameters initialization beside the class name.

You may get the following  error “Feature ‘primary constructor’ is only available in ‘experimental’ language version.” To solve this we need to edit the SolutionName.csproj file to get rid of this error.  What you have to do is we need to add additional setting after WarningTag

<LangVersion>experimental</LangVersion>

Feature 'primary constructor' is only available in 'experimental' language version

Feature ‘primary constructor’ is only available in ‘experimental’ language version

 3. Dictionary Initializer

Before

The old way writing an dictionary initializer is as follows

public class DictionaryInitializerBeforeCSharp6
{
    public Dictionary<string, string> _users = new Dictionary<string, string>()
    {
        {"users", "Venkat Baggu Blog" },
        {"Features", "Whats new in C# 6" }
    };
}

After

We can define dictionary initializer like an array using square brackets

public class DictionaryInitializerInCSharp6
{
    public Dictionary<string, string> _users { get; } = new Dictionary<string, string>()
    {
        ["users"]  = "Venkat Baggu Blog",
        ["Features"] =  "Whats new in C# 6" 
    };
}

4. Declaration Expressions

 Before

public class DeclarationExpressionsBeforeCShapr6()
{
    public static int CheckUserExist(string userId)
    {
        //Example 1
        int id;
        if (!int.TryParse(userId, out id))
        {
            return id;
        }
        return id;
    }

    public static string GetUserRole(long userId)
    {
        ////Example 2
        var user = _userRepository.Users.FindById(x => x.UserID == userId);
        if (user!=null)
        {
            // work with address ...

            return user.City;
        }
    }
}

After

In C# 6 you can declare an local variable in middle of the expression. With declaration expressions we can also declare variables inside if statements and various loop statements

public class DeclarationExpressionsInCShapr6()
{
    public static int CheckUserExist(string userId)
    {
        if (!int.TryParse(userId, out var id))
        {
            return id;
        }
        return 0;
    }

    public static string GetUserRole(long userId)
    {
        ////Example 2
        if ((var user = _userRepository.Users.FindById(x => x.UserID == userId) != null)
        {
            // work with address ...

            return user.City;
        }
    }
}

 5.  Using Statics

Before

To you static members you don’t need an instance of object to invoke a method. You use syntax as follows

TypeName.MethodName

public class StaticUsingBeforeCSharp6
{
    public void TestMethod()
    {
        Console.WriteLine("Static Using Before C# 6");
    }
}

After

In  C# 6 you have the ability to use the Static Members with out using the type name. You can import the static classes in the namespaces.

If you look at the below example we moved the Static Console class to the namespace

using System.Console;
namespace newfeatureincsharp6
{
    public class StaticUsingInCSharp6
    {
        public void TestMethod()
        {
            WriteLine("Static Using Before C# 6");
        }
    }
}

6. await inside catch block

Before C# 6 await keyword is not available inside the catch and finally block. In C# 6 we can finally use the await keyword inside catch and finally blocks.

try 
{	        
	//Do something
}
catch (Exception)
{
	await Logger.Error("exception logging")
}

7. Exception Filters

Exception filters allow you a feature to check an if condition before the catch block excutes.

Consider an example that an exception occurred now we want to check if the InnerException  null then it will executes catch block

//Example 1
try
{
    //Some code
}
catch (Exception ex) if (ex.InnerException == null)
{
    //Do work

}

//Before C# 6 we write the above code as follows

//Example 1
try
{
    //Some code
}
catch (Exception ex) 
{
    if(ex.InnerException != null)
    {
        //Do work;
    }
}

 8. Conditional Access Operator to check NULL Values ?.

Consider an example that we want to retrieve an UserRanking based on the UserID only if UserID is not null.

Before

var userRank = "No Rank";
if(UserID != null)
{
    userRank = Rank;
}

//or

var userRank = UserID != null ? Rank : "No Rank" 

After

var userRank = UserID?.Rank ?? "No Rank";

 

 

 

 

 

 

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