IFormattable F# snippets (#7769)

Author: albert-du

snippets/fsharp/System/IFormattable/Overview/example1.fs

@@ -0,0 +1,92 @@
+// <Snippet1>
+open System
+open System.Globalization
+
+type Temperature(temperature: decimal) =
+    do 
+        if temperature < -273.15M then
+            raise (ArgumentOutOfRangeException $"{temperature} is less than absolute zero.")
+
+    member _.Celsius =
+        temperature
+
+    member _.Fahrenheit =
+        temperature * 9M / 5M + 32M
+
+    member _.Kelvin =
+        temperature + 273.15m
+
+    override this.ToString() =
+        this.ToString("G", CultureInfo.CurrentCulture)
+
+    member this.ToString(format) =
+        this.ToString(format, CultureInfo.CurrentCulture)
+
+    member this.ToString(format, provider: IFormatProvider) =
+        let format =
+            if String.IsNullOrEmpty format then "G"
+            else format
+
+        let provider =
+            if isNull provider then 
+                CultureInfo.CurrentCulture :> IFormatProvider
+            else provider
+
+        match format.ToUpperInvariant() with
+        | "G" | "C" ->
+            temperature.ToString("F2", provider) + " °C"
+        | "F" ->
+            this.Fahrenheit.ToString("F2", provider) + " °F"
+        | "K" ->
+            this.Kelvin.ToString("F2", provider) + " K"
+        | _ ->
+            raise (FormatException $"The {format} format string is not supported.")
+
+    interface IFormattable with
+        member this.ToString(format, provider) = this.ToString(format, provider)
+
+// </Snippet1>
+
+// <Snippet2>
+open System
+open System.Globalization
+
+[<EntryPoint>]
+let main _ =
+    // Use composite formatting with format string in the format item.
+    let temp1 = Temperature 0
+    Console.WriteLine("{0:C} (Celsius) = {0:K} (Kelvin) = {0:F} (Fahrenheit)\n", temp1)
+
+    // Use composite formatting with a format provider.
+    let temp1 = Temperature -40
+    String.Format(CultureInfo.CurrentCulture, "{0:C} (Celsius) = {0:K} (Kelvin) = {0:F} (Fahrenheit)", temp1)
+    |> printfn "%s"
+    String.Format(CultureInfo "fr-FR", "{0:C} (Celsius) = {0:K} (Kelvin) = {0:F} (Fahrenheit)\n", temp1)
+    |> printfn "%s"
+
+    // Call ToString method with format string.
+    let temp1 = Temperature 32
+    Console.WriteLine("{0} (Celsius) = {1} (Kelvin) = {2} (Fahrenheit)\n",
+                      temp1.ToString "C", temp1.ToString "K", temp1.ToString "F")
+
+    // Call ToString with format string and format provider
+    let temp1 = Temperature 100      
+    let current = NumberFormatInfo.CurrentInfo
+    let nl = CultureInfo "nl-NL"
+    Console.WriteLine("{0} (Celsius) = {1} (Kelvin) = {2} (Fahrenheit)",
+                      temp1.ToString("C", current), temp1.ToString("K", current), temp1.ToString("F", current))
+    Console.WriteLine("{0} (Celsius) = {1} (Kelvin) = {2} (Fahrenheit)",
+                      temp1.ToString("C", nl), temp1.ToString("K", nl), temp1.ToString("F", nl))
+    0
+
+// The example displays the following output:
+//    0.00 °C (Celsius) = 273.15 K (Kelvin) = 32.00 °F (Fahrenheit)
+//
+//    -40.00 °C (Celsius) = 233.15 K (Kelvin) = -40.00 °F (Fahrenheit)
+//    -40,00 °C (Celsius) = 233,15 K (Kelvin) = -40,00 °F (Fahrenheit)
+//
+//    32.00 °C (Celsius) = 305.15 K (Kelvin) = 89.60 °F (Fahrenheit)
+//
+//    100.00 °C (Celsius) = 373.15 K (Kelvin) = 212.00 °F (Fahrenheit)
+//    100,00 °C (Celsius) = 373,15 K (Kelvin) = 212,00 °F (Fahrenheit)
+// </Snippet2>

snippets/fsharp/System/IFormattable/Overview/fs.fsproj

@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="example1.fs" />
+  </ItemGroup>
+</Project>

xml/System/IFormattable.xml

@@ -81,11 +81,13 @@
  The following example defines a `Temperature` class that implements the <xref:System.IFormattable> interface. The class supports four format specifiers: "G" and "C", which indicate that the temperature is to be displayed in Celsius; "F", which indicates that the temperature is to be displayed in Fahrenheit; and "K", which indicates that the temperature is to be displayed in Kelvin. In addition, the <xref:System.IFormattable.ToString%2A?displayProperty=nameWithType> implementation also can handle a format string that is `null` or empty. The other two `ToString` methods defined by the `Temperature` class simply wrap a call to the <xref:System.IFormattable.ToString%2A?displayProperty=nameWithType> implementation.  
   
  :::code language="csharp" source="~/snippets/csharp/System/IFormattable/Overview/example1.cs" id="Snippet1":::
+ :::code language="fsharp" source="~/snippets/fsharp/System/IFormattable/Overview/example1.fs" id="Snippet1":::
  :::code language="vb" source="~/snippets/visualbasic/VS_Snippets_CLR_System/system.iformattable/vb/example1.vb" id="Snippet1":::  
   
  The following example then calls the <xref:System.IFormattable.ToString%2A?displayProperty=nameWithType> implementation either directly or by using a composite format string.  
   
  :::code language="csharp" source="~/snippets/csharp/System/IFormattable/Overview/example1.cs" id="Snippet2":::
+ :::code language="fsharp" source="~/snippets/fsharp/System/IFormattable/Overview/example1.fs" id="Snippet2":::
  :::code language="vb" source="~/snippets/visualbasic/VS_Snippets_CLR_System/system.iformattable/vb/example1.vb" id="Snippet2":::  
   
  ]]></format>
@@ -189,6 +191,7 @@
  The following example demonstrates a `Temperature` class that implements the <xref:System.IFormattable.ToString%2A> method. This code example is part of a larger example provided for the <xref:System.IFormattable> class.  
   
  :::code language="csharp" source="~/snippets/csharp/System/IFormattable/Overview/example1.cs" id="Snippet1":::
+ :::code language="fsharp" source="~/snippets/fsharp/System/IFormattable/Overview/example1.fs" id="Snippet1":::
  :::code language="vb" source="~/snippets/visualbasic/VS_Snippets_CLR_System/system.iformattable/vb/example1.vb" id="Snippet1":::  
   
  ]]></format>