自动实现的get中的C＃支持字段背后的代码是什么？ 组;？

Question

I am learning it may be something like this:

public string ModifiedBy {
      get { return m_ModifiedBy ?? string.Empty; }
      set { 
        if(value!=null) {
            m_ModifiedBy = value;
            m_Modified = DateTime.Now;       
        }
      }
    } 

Is this correct or is there more or less involved? I would just like to duplicate exactly what is done with a get; set; that is auto implemented.

Answer 1

It's wrong; your code is doing much more than just getting and setting a string.

An auto-implemented string property ModifiedBy simply expands to the following equivalent manually-implemented property:

// Key difference: the backing field of an automatic property
// is not accessible by your own code
private string m_modifiedBy;

public string ModifiedBy {
    get { return m_modifiedBy; }
    set { m_modifiedBy = value; }
}

That's it. There is no non-null default of string.Empty , no other class members are involved, no null checks, no additional logic, etc. Null values are handled in exactly the same way as any other value.

Answer 2

An auto-implemented property is implemented like this:

private int _foo;   // compiler-generated
public int Foo
{
    get { return _foo; }
    set { _foo = value; }
}

Answer 3

The auto-implemented properties will mostly work like in the following example

// This class is mutable. Its data can be modified from
// outside the class.
class Customer
{
    // Auto-Impl Properties for trivial get and set
    public double TotalPurchases { get; set; }
    public string Name { get; set; }
    public int CustomerID { get; set; }

    // Constructor
    public Customer(double purchases, string name, int ID)
    {
        TotalPurchases = purchases;
        Name = name;
        CustomerID = ID;
    }
    // Methods
    public string GetContactInfo() {return "ContactInfo";}
    public string GetTransactionHistory() {return "History";}

    // .. Additional methods, events, etc.
}


class Program
{

    static void Main()
    {
        // Intialize a new object.
        Customer cust1 = new Customer ( 4987.63, "Northwind",90108 );

        //Modify a property
        cust1.TotalPurchases += 499.99;

    }
}

And in your code part you shouldn't check for null values, because if the null is set to the property then it will not work.

Answer 4

You can see the actual code that get's created by the compiler by decompiling it with ILSpy. Check here for an example of what get's generated.