C# Automatic Properties - Why Do I Have To Write “get; set;”?

Question

If both get and set are compulsory in C# automatic properties, why do I have to bother specifying \"get; set;\" at all?

Answer 1

Just thought I would share my findings on this topic.

Coding a property like the following, is a .net 3.0 shortcut call “auto-implemented property”.

public int MyProperty { get; set; }

This saves you some typing. The long way to declare a property is like this:

private int myProperty;
public int MyProperty 
{
  get { return myProperty; }
  set { myProperty = value; } 
}

When you use the “auto-implemented property” the compiler generates the code to wire up the get and set to some “k_BackingField”. Below is the disassembled code using Reflector.

public int MyProperty
{
    [CompilerGenerated]
    get
    {
        return this.k__BackingField;
    }
    [CompilerGenerated]
    set
    {
        this.k__BackingField = value;
    }
}

disassembled C# code from IL

Also wires up a method for the setter and getter.

[CompilerGenerated]
public void set_MyProperty(int value)
{
    this.k__BackingField = value;
}
[CompilerGenerated]
public int get_MyProperty()
{
    return this.k__BackingField;
}

disassembled C# code from IL

When you declare a read only auto-implemented property, by setting the setter to private:

 public int MyProperty { get; private set; }

All the compiler does flag the "set" as private. The setter and getter method say the same.

public int MyProperty
{
    [CompilerGenerated]
    get
    {
        return this.k__BackingField;
    }
    private [CompilerGenerated]
    set
    {
        this.k__BackingField = value;
    }
}

disassembled C# code from IL

So I am not sure why the framework require both the get; and set; on an auto-implemented property. They could have just not written the set and setter method if it was not supplied. But there may be some compiler level issue that makes this difficult, I don't know.

If you look at the long way of declaring a read only property:

public int myProperty = 0;
public int MyProperty
{
    get { return myProperty; }
}  

And then look at the disassembled code. The setter is not there at all.

public int Test2
{
    get
    {
        return this._test;
    }
}

public int get_Test2()
{
    return this._test;
}

disassembled C# code from IL