[C#] Object Initializers, Collection Initializers

• 由於 Auto-implemented properties 的用法產生，也連同產生出新的 Object Initializers, Collection Initializers
• Code

public class User
{
    // Auto-implemented properties.
    public string Name { get; set; }
    public int Age { get; set; }
}
C#

• Object Initializers
• Code
• 一般用法

public class Initializers
{
    public void function()
    {
        User user = new User();
        user.Name = "Lyndon";
        user.Age = 30;
    }
}
C#

• Code
• syntactic sugar 語言特性來簡化

public class Initializers
{
    public void function()
    {
        User user = new User() { Name = "Lyndon", Age = 30 };
    }
}
C#

• Collection Initializers
• Code 2.0

public class Initializers
{
    public void function()
    {
        List< User> lUser = new List< User>();
        lUser.Add( new User { Name = "Helen", Age = 25 } );
        lUser.Add( new User { Name = "Lyndon", Age = 30 } );
        lUser.Add( new User { Name = "Daisy", Age = 27 } );
    }
}
C#

• Code 3.0 (Orcas version)

public class Initializers
    {
        public void function()
        {
            List< User> lUser = new List< User>()
            {
                new User { Name = "Helen", Age = 25 },
                new User { Name = "Lyndon", Age = 30 },
                new User { Name = "Daisy", Age = 27 }
            };
        }
    }
C#

public class Initializers
{
    public void function()
    {
        Dictionary< int, User> students = new Dictionary< int, User>()
        {
            { 111, new User { Name = "Helen", Age = 25 }},
            { 112, new User { Name = "Lyndon", Age = 30 }},
            { 113, new User { Name = "Daisy", Age = 27 }}
        };
    }
}
C#

• Code 3.0 固定記憶體大小
• 一般陣列宣告後，會給固定的記憶體大小

public class Initializers
{
    public void function()
    {
        List< User> lUser = new List< User>(3)
        {
            new User { Name = "Helen", Age = 25 },
            new User { Name = "Lyndon", Age = 30 },
            new User { Name = "Daisy", Age = 27 }
        };
    }
}
C#

• Ref
• https://weblogs.asp.net/scottgu/new-c-orcas-language-features-automatic-properties-object-initializers-and-collection-initializers
• https://docs.microsoft.com/zh-tw/dotnet/csharp/programming-guide/classes-and-structs/object-and-collection-initializers
• https://docs.microsoft.com/zh-tw/dotnet/csharp/programming-guide/classes-and-structs/object-and-collection-initializers