Why Automatically implemented properties must define both get and set accessors

Question

When we define a property like

    public string Name {get; set;}

dot net can make our properties code. but when we use

Answer 1

Because the auto-implemented properties generate their own backing store for the property values. You have no access to the internal store.

Implementing a property with

• just get : means you can only retrieve the values. You can't ever set the property value (even in the containing class)
• just set : means you can only set the values. You can't retrieve the property value.

for a normal property

private int _data;
public int Data{  get { return _data } };

Here the parent class can do the following somewhere else in the class ( which it can't with auto props)

_data = 100;

Note: You can define an auto-prop like this (which is how I use it the most).

public int Data { get; private set;}

This means that the property can't be set by external clients of the class. However the containing class itself can set the property multiple times via this.Data = x; within the class definition.

Answer 2

If there is no setter, the property can never have anything other than the default value, so doesn't serve any purpose.

Answer 3

A more modern scenario for receiving this error is building code that uses C#6 syntax using a version of VisualStudio that is less than VS 2015 (or using MsBuild that is less than 14).

In C#6.0 it is allowable to have autoProperties that do not have a setter (they are assumed to be a private set).

Try compiling with VS2015+ or msbuild 14+ .. or modify the code so that all autoProperties have a setter.