In C# 3.0 and later, auto-implemented properties make property-declaration more concise when no additional logic is required in the property accessors. They also enable client code to create objects When you declare a property as shown in the following example, the compiler creates a private, anonymous backing field can only be accessed through the property's get and set accessors.

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Contrary to what the documentation suggests, it is not possible to define an auto-implemented property that uses the same behavior as the C# readonly keyword (when applied to an explicit backing field). The link to the readonly topic should be removed, at the very least.

Using private set will define an auto-implemented property with a read-only public contract, although this leaves open the possibility for the value to change after the constructor has been invoked; behavior that is prevented by defining a property without a set accessor and applying the readonly keyword to the backing field.

[http://msdn.microsoft.com/en-us/library/bb384054.aspx]