dotnet · BillWagner · Feb 28, 2022 · Feb 26, 2022
@@ -0,0 +1,93 @@
+module EqualsEx2
+
+// <Snippet3>
+open System
+open System.Text.RegularExpressions
+
+type Person(lastName, ssn) =
+    let mutable lastName = lastName
+    let ssn = 
+        if Regex.IsMatch(ssn, @"\d{9}") then
+            $"{ssn.Substring(0, 3)}-{ssn.Substring(3, 2)}-{ssn.Substring(5, 4)}"
+        elif Regex.IsMatch(ssn, @"\d{3}-\d{2}-\d{4}") then
+            ssn
+        else
+            raise (FormatException "The social security number has an invalid format.")
+
+    member _.SSN =
+        ssn
+
+    member _.LastName
+        with get () = lastName
+        and set (value) =
+            if String.IsNullOrEmpty value then
+                invalidArg (nameof value) "The last name cannot be null or empty."
+            else
+                lastName <- value
+
+    static member op_Equality (person1: Person, person2: Person) =
+        if box person1 |> isNull || box person2 |> isNull then
+            Object.Equals(person1, person2)
+        else
+            person1.Equals person2
+
+    static member op_Inequality (person1: Person, person2: Person) =
+        if box person1 |> isNull || box person2 |> isNull then
+            Object.Equals(person1, person2) |> not
+        else
+            person1.Equals person2 |> not
+
+    override _.GetHashCode() =
+        ssn.GetHashCode()
+
+    override this.Equals(obj: obj) =
+        match obj with 
+        | :? Person as personObj ->
+            (this :> IEquatable<_>).Equals personObj
+        | _ -> false
+
+    interface IEquatable<Person> with
+        member this.Equals(other: Person) =
+            match box other with 
+            | null -> false
+            | _ ->
+                this.SSN = other.SSN
+// </Snippet3>
+// Create a Person object for each job applicant.
+let applicant1 = Person("Jones", "099-29-4999")
+let applicant2 = Person("Jones", "199-29-3999")
+let applicant3 = Person("Jones", "299-49-6999")
+
+// Add applicants to a List object.
+let applicants = ResizeArray()
+applicants.Add applicant1
+applicants.Add applicant2
+applicants.Add applicant3
+
+// Create a Person object for the final candidate.
+let candidate = Person("Jones", "199-29-3999")
+if applicants.Contains candidate then
+    printfn $"Found {candidate.LastName} (SSN {candidate.SSN})."
+else
+    printfn $"Applicant {candidate.SSN} not found."
+
+// Call the shared inherited Equals(Object, Object) method.
+// It will in turn call the IEquatable<T>.Equals implementation.
+printfn $"{applicant2.LastName}({applicant2.SSN}) already on file: {Person.Equals(applicant2, candidate)}."
+
+// The example displays the following output:
+//       Found Jones (SSN 199-29-3999).
+//       Jones(199-29-3999) already on file: True.
+
+// This tests the handling of null values, but does not appear in the documentation.
+//
+//public class Example
+//{
+//   public static void Main()
+//   {
+//      var p1 = new Person("Joe", "613-24-0068")
+//      Person p2 = null
+//
+//      Console.WriteLine(p1 == p2)
+//   }
+//}
@@ -0,0 +1,80 @@
+open System
+open System.Collections.Generic
+open System.Text.RegularExpressions
+
+type Person(lastName, ssn) =
+    let mutable lastName = lastName
+    let ssn = 
+        if Regex.IsMatch(ssn, @"\d{9}") then
+            $"{ssn.Substring(0, 3)}-{ssn.Substring(3, 2)}-{ssn.Substring(5, 4)}"
+        elif Regex.IsMatch(ssn, @"\d{3}-\d{2}-\d{4}") then
+            ssn
+        else
+            raise (FormatException "The social security number has an invalid format.")
+
+    member _.SSN =
+        ssn
+
+    member _.LastName
+        with get () = lastName
+        and set (value) =
+            if String.IsNullOrEmpty value then
+                invalidArg (nameof value) "The last name cannot be null or empty."
+            else
+                lastName <- value
+
+    static member op_Equality (person1: Person, person2: Person) =
+        if box person1 |> isNull || box person2 |> isNull then
+            Object.Equals(person1, person2)
+        else
+            person1.Equals person2
+
+    static member op_Inequality (person1: Person, person2: Person) =
+        if box person1 |> isNull || box person2 |> isNull then
+            Object.Equals(person1, person2) |> not
+        else
+            person1.Equals person2 |> not
+
+    override _.GetHashCode() =
+        ssn.GetHashCode()
+
+    override this.Equals(obj: obj) =
+        match obj with 
+        | :? Person as personObj ->
+            (this :> IEquatable<_>).Equals personObj
+        | _ -> false
+
+    interface IEquatable<Person> with
+        member this.Equals(other: Person) =
+            match box other with 
+            | null -> false
+            | _ ->
+                this.SSN = other.SSN
+
+// <Snippet12>
+// Create a Person object for each job applicant.
+let applicant1 = Person("Jones", "099-29-4999")
+let applicant2 = Person("Jones", "199-29-3999")
+let applicant3 = Person("Jones", "299-49-6999")
+
+// Add applicants to a List object.
+let applicants = ResizeArray()
+applicants.Add applicant1
+applicants.Add applicant2
+applicants.Add applicant3
+
+// Create a Person object for the final candidate.
+let candidate = Person("Jones", "199-29-3999")
+if applicants.Contains candidate then
+    printfn $"Found {candidate.LastName} (SSN {candidate.SSN})."
+else
+    printfn $"Applicant {candidate.SSN} not found."
+
+// Call the shared inherited Equals(Object, Object) method.
+// It will in turn call the IEquatable<T>.Equals implementation.
+printfn $"{applicant2.LastName}({applicant2.SSN}) already on file: {Person.Equals(applicant2, candidate)}."
+
+// The example displays the following output:
+//       Found Jones (SSN 199-29-3999).
+//       Jones(199-29-3999) already on file: True.
+// </Snippet12>
@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="EqualsEx2.fs" />
+    <Compile Include="Snippet12.fs" />
+  </ItemGroup>
+</Project>
@@ -145,11 +145,13 @@
  The following example shows the partial implementation of a `Person` class that implements <xref:System.IEquatable%601> and has two properties, `LastName` and `SSN`. The <xref:System.IEquatable%601.Equals%2A> method returns `True` if the `SSN` property of two `Person` objects is identical; otherwise, it returns `False`.  
 
  :::code language="csharp" source="~/snippets/csharp/System/IEquatableT/Equals/EqualsEx2.cs" id="Snippet3":::
+ :::code language="fsharp" source="~/snippets/fsharp/System/IEquatableT/Equals/EqualsEx2.fs" id="Snippet3":::
  :::code language="vb" source="~/snippets/visualbasic/VS_Snippets_CLR_System/system.GenericIEquatable.Equals/vb/EqualsEx2.vb" id="Snippet3":::  
 
  `Person` objects can then be stored in a <xref:System.Collections.Generic.List%601> object and can be identified by the `Contains` method, as the following example shows.  
 
  :::code language="csharp" source="~/snippets/csharp/System/IEquatableT/Equals/Snippet12.cs" id="Snippet12":::
+ :::code language="fsharp" source="~/snippets/fsharp/System/IEquatableT/Equals/Snippet12.fs" id="Snippet12":::
  :::code language="vb" source="~/snippets/visualbasic/VS_Snippets_CLR_System/system.GenericIEquatable.Equals/vb/Snippet12.vb" id="Snippet12":::  
 
  ]]></format>