Examples of Immutable Types in .Net

Question

We know the concept of immutability but need to know few immutable types other than

• String
• DateTime

Are there more?

Answer 1

A list of immutable types in the framework class library follows below. (Feel free to expand it!)

System.…

• All primitive value types: ^{(Note: not all value types are immutable!)}
  • Byte and SByte
  • Int16 and UInt16
  • Int32 and UInt32
  • Int64 and UInt64
  • IntPtr
  • Single
  • Double
• Decimal
• All anonymous types created by the compiler (new { ... } in C#, New With { ... } in VB.NET) ^{(Wrong for two reasons: These types are not in the FCL, and apparently VB.NET types are mutable.)}
• All enumeration types (enum, Enum)
• All delegate types. ^{(see this answer. While it might seem that delegates are mutable (since you can do things like obj.PropertyChanged += callback, it's actually the obj.PropertyChanged reference that is mutated to point to a newly constructed delegate instance; the original delegate instance stays unchanged.)}
• DateTime, TimeSpan ^{(mentioned in this answer)} and DateTimeOffset
• DBNull
• Guid
• Nullable<T>
• String
• The Tuple<…> types introduced with .NET 4 ^{(mentioned in this answer)}
• Uri
• Version
• Void

System.Linq.…

• Lookup<TKey, TElement>