.NET Properties - Use Private Set or ReadOnly Property?
In what situation should I use a Private Set on a property versus making it a ReadOnly property? Take into consideration the two very simplistic examples below.
First example:
Public Class Person Private _name As String Public Property Name As String Get Return _name End Get Private Set(ByVal value As String) _name = value End Set End Property Public Sub WorkOnName() Dim txtInfo As TextInfo = _ Threading.Thread.CurrentThread.CurrentCulture.TextInfo Me.Name = txtInfo.ToTitleCase(Me.Name) End Sub End Class // ---------- public class Person { private string _name; public string Name { get { return _name; } private set { _name = value; } } public void WorkOnName() { TextInfo txtInfo = System.Threading.Thread.CurrentThread.CurrentCulture.TextInfo; this.Name = txtInfo.ToTitleCase(this.Name); } }Second example:
Public Class AnotherPerson Private _name As String Public ReadOnly Property Name As String Get Return _name End Get End Property Public Sub WorkOnName() Dim txtInfo As TextInfo = _ Threading.Thread.CurrentThread.CurrentCulture.TextInfo _name = txtInfo.ToTitleCase(_name) End Sub End Class // --------------- public class AnotherPerson { private string _name; public string Name { get { return _name; } } public void WorkOnName() { TextInfo txtInfo = System.Threading.Thread.CurrentThread.CurrentCulture.TextInfo; _name = txtInfo.ToTitleCase(_name); } }They both yield the same results. Is this a situation where there's no right and wrong, and it's just a matter of preference?
There are a couple reasons to use
private set.1) If you are not using a backing field at all and want a read-only automatic property:
public string Name { get; private set; } public void WorkOnName() { TextInfo txtInfo = Thread.CurrentThread.CurrentCulture.TextInfo; Name = txtInfo.ToTitleCase(Name); }2) If you want to do extra work when you modify the variable inside your class and want to capture that in a single location:
private string _name = string.Empty; public string Name { get { return _name; } private set { TextInfo txtInfo = Thread.CurrentThread.CurrentCulture.TextInfo; _name = txtInfo.ToTitleCase(value); } }In general, though, it's a matter of personal preference. Far as I know, there are no performance reasons to use one over the other.
Just adding this because the question also has a vb.net tag, but in vb.net you need to specify a backer if you use private on either either get or set. So in vb.net it's actually less work to make the property readonly I think.
I never knew about that `private set`. :-)
An update for those reading this answer in 2016. C# 6.0 has introduced readonly auto-properties, which allow you to have a readonly property without a backing field: `public string Name { get; }`. If you don't want a mutable property, that's the preferred syntax now.
One very good reason not to use `private set` is that it's not as immutable as we like to pretend it is. If you want to implement a truly immutable class, read only is a must.
May be a performance reason to NOT use readonly. Seems to cause unnecessary copying of structs when accessing methods of a readonly struct field. https://codeblog.jonskeet.uk/2014/07/16/micro-optimization-the-surprising-inefficiency-of-readonly-fields/
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Content dated before 6/26/2020 9:53 AM
samis 3 years ago
`public string Name { get; protected set; }` through inheritance.