System.FormatException F# snippets (#7727)

* FormatException F# snippets

* fix project file

Author: albert-du

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

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+module example1
+
+// <Snippet1>
+open System
+
+type TemperatureScale =
+    | Celsius = 0
+    | Fahrenheit = 1
+    | Kelvin = 2
+
+let getCurrentTemperature () =
+    let dat = DateTime.Now
+    let temp = 20.6m
+    let scale = TemperatureScale.Celsius
+    String.Format("At {0:t} on {1:D}, the temperature is {2:F1} {3:G}", dat, temp, scale)
+
+getCurrentTemperature ()
+|> printfn "%s"
+
+// The example displays output like the following:
+//    Unhandled Exception: System.FormatException: Format specifier was invalid.
+//       at System.Number.NumberToString(ValueStringBuilder& sb, NumberBuffer& number, Char format, Int32 nMaxDigits, NumberFormatInfo info)   
+//       at System.Number.TryFormatDecimal(Decimal value, ReadOnlySpan`1 format, NumberFormatInfo info, Span`1 destination, Int32& charsWritten)
+//       at System.Decimal.TryFormat(Span`1 destination, Int32& charsWritten, ReadOnlySpan`1 format, IFormatProvider provider)       
+//       at System.Text.ValueStringBuilder.AppendFormatHelper(IFormatProvider provider, String format, ParamsArray args)
+//       at System.String.FormatHelper(IFormatProvider provider, String format, ParamsArray args)
+//       at System.String.Format(String format, Object arg0, Object arg1, Object arg2)
+//       at Example.getCurrentTemperature()
+//       at <StartupCode$fs>.$Example.main@()
+// </Snippet1>

snippets/fsharp/System/FormatException/Overview/example2.fs

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+module example2
+
+// <Snippet2>
+open System
+
+type TemperatureScale =
+    | Celsius = 0
+    | Fahrenheit = 1
+    | Kelvin = 2
+
+let getCurrentTemperature () =
+    let dat = DateTime.Now
+    let temp = 20.6m
+    let scale = TemperatureScale.Celsius
+    String.Format("At {0:t} on {0:D}, the temperature is {1:F1} {2:G}", dat, temp, scale)
+
+getCurrentTemperature ()
+|> printfn "%s"
+
+// The example displays output like the following:
+//    At 10:40 AM on Wednesday, June 04, 2014, the temperature is 20.6 Celsius
+// </Snippet2>

snippets/fsharp/System/FormatException/Overview/example3.fs

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+module example3
+
+open System
+
+let n1 = 10
+let n2 = 20
+// <Snippet4>
+let result = String.Format("{0} + {1} = {2}", n1, n2, n1 + n2)
+// </Snippet4>
+printfn $"{result}"
+
+do
+    // <Snippet3>
+    let n1 = 10
+    let n2 = 20
+    String result = String.Format("{0 + {1] = {2}",
+                                n1, n2, n1 + n2)
+    // </Snippet3>
+    |> ignore

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

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+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="example1.fs" />
+    <Compile Include="example2.fs" />
+    <Compile Include="example3.fs" />
+    <Compile Include="iformattable1.fs" />
+    <Compile Include="iformattable2.fs" />
+    <Compile Include="iformattable3.fs" />
+    <Compile Include="iformattable4.fs" />
+    <Compile Include="qa1.fs" />
+    <Compile Include="qa2.fs" />
+    <Compile Include="qa3.fs" />
+  </ItemGroup>
+</Project>

snippets/fsharp/System/FormatException/Overview/iformattable1.fs

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+module ifromattable1
+
+// <Snippet7>
+let price = 169.32m
+printfn $"The cost is {price:Q2}."
+// The example displays the following output:
+//    Unhandled Exception: System.FormatException: Format specifier was invalid.
+//       at System.Number.NumberToString(ValueStringBuilder& sb, NumberBuffer& number, Char format, Int32 nMaxDigits, NumberFormatInfo info)
+//       at System.Number.TryFormatDecimal(Decimal value, ReadOnlySpan`1 format, NumberFormatInfo info, Span`1 destination, Int32& charsWritten)
+//       at System.Decimal.TryFormat(Span`1 destination, Int32& charsWritten, ReadOnlySpan`1 format, IFormatProvider provider)
+//       at System.Text.ValueStringBuilder.AppendFormatHelper(IFormatProvider provider, String format, ParamsArray args)
+//       at System.String.FormatHelper(IFormatProvider provider, String format, ParamsArray args)
+//       at [email protected](Object vobj)
+//       at Microsoft.FSharp.Core.PrintfImpl.PrintfEnv`3.RunSteps(Object[] args, Type[] argTys, Step[] steps)
+//       at Microsoft.FSharp.Core.PrintfModule.gprintf[a,TState,TResidue,TResult,TPrinter](FSharpFunc`2 envf, PrintfFormat`4 format)
+//       at <StartupCode$fs>.$Example.main@()
+// </Snippet7>

snippets/fsharp/System/FormatException/Overview/iformattable2.fs

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+module iformattable2
+
+// <Snippet8>
+let price = 169.32m
+printfn $"The cost is {price:C2}."
+// The example displays the following output:
+//    The cost is $169.32.
+// </Snippet8>

snippets/fsharp/System/FormatException/Overview/iformattable3.fs

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+module iformattable3
+
+// <Snippet9>
+open System
+
+let guidString = "ba748d5c-ae5f-4cca-84e5-1ac5291c38cb"
+printfn $"""{Guid.ParseExact(guidString, "G")}"""
+// The example displays the following output:
+//    Unhandled Exception: System.FormatException:
+//       Format String can be only "D", "d", "N", "n", "P", "p", "B", "b", "X" or "x".
+//       at System.Guid.ParseExact(String input, String format)
+//       at <StartupCode$fs>.$Example.main@()
+// </Snippet9>

snippets/fsharp/System/FormatException/Overview/iformattable4.fs

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+module iformattable4
+
+// <Snippet10>
+open System
+
+let guidString = "ba748d5c-ae5f-4cca-84e5-1ac5291c38cb"
+printfn $"{Guid.Parse guidString}"
+// The example displays the following output:
+//    ba748d5c-ae5f-4cca-84e5-1ac5291c38cb
+// </Snippet10>

snippets/fsharp/System/FormatException/Overview/qa1.fs

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+module qa1
+
+// <Snippet5>
+open System
+
+let rnd = Random()
+let numbers = Array.zeroCreate<int> 4
+let mutable total = 0
+for i = 0 to 2 do
+    let number = rnd.Next 1001
+    numbers[i] <- number
+    total <- total + number
+numbers[3] <- total
+Console.WriteLine("{0} + {1} + {2} = {3}", numbers)
+
+// The example displays the following output:
+//    Unhandled Exception:
+//    System.FormatException:
+//       Index (zero based) must be greater than or equal to zero and less than the size of the argument list.
+//       at System.Text.StringBuilder.AppendFormat(IFormatProvider provider, String format, Object[] args)
+//       at System.IO.TextWriter.WriteLine(String format, Object arg0)
+//       at System.IO.TextWriter.SyncTextWriter.WriteLine(String format, Object arg0)
+//       at <StartupCode$fs>.$Example.main@()
+// </Snippet5>

snippets/fsharp/System/FormatException/Overview/qa2.fs

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+module qa2
+
+// <Snippet6>
+open System
+
+let rnd = Random()
+let numbers = Array.zeroCreate<int> 4
+let mutable total = 0
+for i = 0 to 2 do
+    let number = rnd.Next 1001
+    numbers[i] <- number
+    total <- total + number
+numbers[3] <- total
+let values = Array.zeroCreate<obj> numbers.Length
+numbers.CopyTo(values, 0)
+Console.WriteLine("{0} + {1} + {2} = {3}", values)
+// The example displays output like the following:
+//        477 + 956 + 901 = 2334
+// </Snippet6>