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System.Exception F# snippets (#7725)
* Exception F# snippets * fix link
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‎snippets/fsharp/System/Exception/.ctor/fs.fsproj‎

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<Project Sdk="Microsoft.NET.Sdk">
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<PropertyGroup>
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<OutputType>Exe</OutputType>
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<TargetFramework>net48</TargetFramework>
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</PropertyGroup>
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<ItemGroup>
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<Compile Include="new.fs" />
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<Compile Include="news.fs" />
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<Compile Include="getobjdata.fs" />
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<Compile Include="newsi.fs" />
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</ItemGroup>
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<ItemGroup>
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<Reference Include="System.Runtime.Serialization.Formatters.Soap" />
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</ItemGroup>
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</Project>

‎snippets/fsharp/System/Exception/.ctor/getobjdata.fs‎

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module NDP_UE_FS_3
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//<Snippet1>
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open System
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open System.IO
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open System.Runtime.Serialization
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open System.Runtime.Serialization.Formatters.Soap
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open System.Security.Permissions
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// Define a serializable derived exception class.
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[<Serializable>]
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type SecondLevelException =
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inherit Exception
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interface ISerializable with
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// GetObjectData performs a custom serialization.
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[<SecurityPermissionAttribute(SecurityAction.Demand,SerializationFormatter=true)>]
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member this.GetObjectData(info: SerializationInfo, context: StreamingContext) =
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// Change the case of two properties, and then use the
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// method of the base class.
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this.HelpLink <- this.HelpLink.ToLower()
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this.Source <- this.Source.ToUpperInvariant()
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base.GetObjectData( info, context )
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// This public constructor is used by class instantiators.
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new (message: string, inner: Exception) as this =
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{ inherit Exception(message, inner) }
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then
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this.HelpLink <- "http://MSDN.Microsoft.com"
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this.Source <- "Exception_Class_Samples"
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// This protected constructor is used for deserialization.
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new (info: SerializationInfo, context: StreamingContext) =
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{ inherit Exception(info, context) }
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printfn
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"""This example of the Exception constructor and Exception.GetObjectData
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with SerializationInfo and StreamingContext parameters generates
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the following output.
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"""
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try
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// This code forces a division by 0 and catches the
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// resulting exception.
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try
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let zero = 0
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let ecks = 1 / zero
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()
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with ex ->
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// Create a new exception to throw again.
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let newExcept = SecondLevelException("Forced a division by 0 and threw another exception.", ex)
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printfn "Forced a division by 0, caught the resulting exception, \nand created a derived exception:\n"
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printfn $"HelpLink: {newExcept.HelpLink}"
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printfn $"Source: {newExcept.Source}"
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// This FileStream is used for the serialization.
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use stream = new FileStream("NewException.dat", FileMode.Create)
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try
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// Serialize the derived exception.
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let formatter = SoapFormatter(null, StreamingContext StreamingContextStates.File)
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formatter.Serialize(stream, newExcept)
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// Rewind the stream and deserialize the
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// exception.
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stream.Position <- 0L
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let deserExcept = formatter.Deserialize stream :?> SecondLevelException
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printfn
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"""
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Serialized the exception, and then deserialized the resulting stream into a
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new exception. The deserialization changed the case of certain properties:
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"""
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// Throw the deserialized exception again.
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raise deserExcept
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with :? SerializationException as se ->
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printfn $"Failed to serialize: {se}"
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with ex ->
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printfn $"HelpLink: {ex.HelpLink}"
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printfn $"Source: {ex.Source}"
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printfn $"\n{ex}"
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// This example displays the following output.
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// Forced a division by 0, caught the resulting exception,
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// and created a derived exception:
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//
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// HelpLink: http://MSDN.Microsoft.com
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// Source: Exception_Class_Samples
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//
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// Serialized the exception, and then deserialized the resulting stream into a
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// new exception. The deserialization changed the case of certain properties:
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//
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// HelpLink: http://msdn.microsoft.com
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// Source: EXCEPTION_CLASS_SAMPLES
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//
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// NDP_UE_FS_3+SecondLevelException: Forced a division by 0 and threw another except
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// ion. ---> System.DivideByZeroException: Attempted to divide by zero.
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// at <StartupCode$fs>.$NDP_UE_FS_3.main@()
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// --- End of inner exception stack trace ---
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// at <StartupCode$fs>.$NDP_UE_FS_3.main@()
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//</Snippet1>

‎snippets/fsharp/System/Exception/.ctor/new.fs‎

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module NDP_UE_FS
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//<Snippet1>
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// Example for the Exception() constructor.
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open System
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// Derive an exception with a predefined message.
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type NotEvenException() =
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inherit Exception "The argument to a function requiring even input is not divisible by 2."
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// half throws a base exception if the input is not even.
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let half input =
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if input % 2 <> 0 then
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raise (Exception())
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else input / 2
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// half2 throws a derived exception if the input is not even.
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let half2 input =
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if input % 2 <> 0 then
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raise (NotEvenException())
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else input / 2
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// calcHalf calls Half and catches any thrown exceptions.
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let calcHalf input =
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try
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let halfInput = half input
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printfn $"Half of {input} is {halfInput}."
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with ex ->
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printfn $"{ex}"
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// calcHalf2 calls Half2 and catches any thrown exceptions.
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let calcHalf2 input =
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try
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let halfInput = half2 input
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printfn $"Half of {input} is {halfInput}."
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with ex ->
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printfn $"{ex}"
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printfn "This example of the Exception() constructor generates the following output."
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printfn "\nHere, an exception is thrown using the \nparameterless constructor of the base class.\n"
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calcHalf 12
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calcHalf 15
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printfn "\nHere, an exception is thrown using the \nparameterless constructor of a derived class.\n"
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calcHalf2 24
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calcHalf2 27
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// This example of the Exception() constructor generates the following output.
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// Here, an exception is thrown using the
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// parameterless constructor of the base class.
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//
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// Half of 12 is 6.
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// System.Exception: Exception of type 'System.Exception' was thrown.
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// at NDP_UE_FS.half(Int32 input)
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// at at NDP_UE_FS.calcHalf(Int32 input)
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//
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// Here, an exception is thrown using the
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// parameterless constructor of a derived class.
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//
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// Half of 24 is 12.
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// NDP_UE_FS+NotEvenException: The argument to a function requiring even input is
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// not divisible by 2.
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// at NDP_UE_FS.half2(Int32 input)
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// at NDP_UE_FS.calcHalf2(Int32 input)
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//</Snippet1>

‎snippets/fsharp/System/Exception/.ctor/news.fs‎

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module NDP_UE_FS_2
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//<Snippet2>
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// Example for the Exception(string) constructor.
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open System
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let notEvenMessage = "The argument to a function requiring even input is not divisible by 2."
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// Derive an exception with a specifiable message.
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type NotEvenException =
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inherit Exception
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new () = { inherit Exception(notEvenMessage) }
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new (auxMessage) = { inherit Exception($"{auxMessage} - {notEvenMessage}") }
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// half throws a base exception if the input is not even.
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let half input =
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if input % 2 <> 0 then
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raise (Exception $"The argument {input} is not divisible by 2.")
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else input / 2
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// half2 throws a derived exception if the input is not even.
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let half2 input =
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if input % 2 <> 0 then
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raise (NotEvenException $"Invalid argument: {input}")
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else input / 2
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// calcHalf calls Half and catches any thrown exceptions.
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let calcHalf input =
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try
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let halfInput = half input
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printfn $"Half of {input} is {halfInput}."
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with ex ->
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printfn $"{ex}"
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// calcHalf2 calls Half2 and catches any thrown exceptions.
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let calcHalf2 input =
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try
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let halfInput = half2 input
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printfn $"Half of {input} is {halfInput}."
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with ex ->
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printfn $"{ex}"
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printfn "This example of the Exception(string)\nconstructor generates the following output."
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printfn "\nHere, an exception is thrown using the \nconstructor of the base class.\n"
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calcHalf 18
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calcHalf 21
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printfn "\nHere, an exception is thrown using the \nconstructor of a derived class.\n"
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calcHalf2 30
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calcHalf2 33
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// This example of the Exception(string)
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// constructor generates the following output.
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//
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// Here, an exception is thrown using the
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// constructor of the base class.
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//
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// Half of 18 is 9.
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// System.Exception: The argument 21 is not divisible by 2.
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// at NDP_UE_FS_2.half(Int32 input)
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// at NDP_UE_FS_2.calcHalf(Int32 input)
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//
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// Here, an exception is thrown using the
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// constructor of a derived class.
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//
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// Half of 30 is 15.
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// NDP_UE_FS_2+NotEvenException: Invalid argument: 33 - The argument to a function r
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// equiring even input is not divisible by 2.
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// at NDP_UE_FS_2.half2(Int32 input)
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// at NDP_UE_FS_2.calcHalf2(Int32 input)
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//</Snippet2>

‎snippets/fsharp/System/Exception/.ctor/newsi.fs‎

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module NDP_UE_FS_4
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//<Snippet3>
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// Example for the Exception(string, Exception) constructor.
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open System
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let overflowMessage = "The log table has overflowed."
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// Derive an exception with a specifiable message and inner exception.
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type LogTableOverflowException =
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inherit Exception
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new () = { inherit Exception(overflowMessage) }
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new (auxMessage: string) =
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{ inherit Exception($"{overflowMessage} - {auxMessage}") }
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new (auxMessage: string, inner: Exception) =
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{ inherit Exception($"{overflowMessage} - {auxMessage}", inner ) }
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type LogTable(numElements: int) =
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let mutable logArea = Array.zeroCreate<string> numElements
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let mutable elemInUse = 0
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// The AddRecord method throws a derived exception
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// if the array bounds exception is caught.
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member _.AddRecord(newRecord: string): int =
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try
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logArea[elemInUse] <- newRecord
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elemInUse <- elemInUse + 1
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elemInUse - 1
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with ex ->
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raise (LogTableOverflowException($"Record \"{newRecord}\" was not logged.", ex ) )
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// Create a log table and force an overflow.
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let log = LogTable 4
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printfn "This example of the Exception(string, Exception)\nconstructor generates the following output."
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printfn "\nExample of a derived exception that references an inner exception:\n"
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try
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for count = 1 to 1000 do
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log.AddRecord $"Log record number {count}"
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|> ignore
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with ex ->
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printfn $"{ex}"
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// This example of the Exception(string, Exception)
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// constructor generates the following output.
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//
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// Example of a derived exception that references an inner exception:
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//
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// NDP_UE_FS_4+LogTableOverflowException: The log table has overflowed. - Record "Lo
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// g record number 5" was not logged. ---> System.IndexOutOfRangeException: Index
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// was outside the bounds of the array.
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// at NDP_UE_FS_4.LogTable.AddRecord(String newRecord)
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// --- End of inner exception stack trace ---
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// at NDP_UE_FS_4.LogTable.AddRecord(String newRecord)
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// at <StartupCode$fs>.$NDP_UE_FS_4.main@()
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//</Snippet3>

‎snippets/fsharp/System/Exception/Data/data.fs‎

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//<snippet1>
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// This example demonstrates the Exception.Data property.
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open System
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open System.Collections
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let nestedRoutine2 displayDetails =
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let e = Exception "This statement is the original exception message."
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if displayDetails then
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let s = "Information from nestedRoutine2."
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let i = -903
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let dt = DateTime.Now
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e.Data.Add("stringInfo", s)
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e.Data["IntInfo"] <- i
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e.Data["DateTimeInfo"] <- dt
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raise e
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let nestedRoutine1 displayDetails =
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try
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nestedRoutine2 displayDetails
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with e ->
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e.Data["ExtraInfo"] <- "Information from nestedRoutine1."
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e.Data.Add("MoreExtraInfo", "More information from nestedRoutine1.")
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reraise ()
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let runTest displayDetails =
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try
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nestedRoutine1 displayDetails
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with e ->
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printfn "An exception was thrown."
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printfn $"{e.Message}"
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if e.Data.Count > 0 then
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printfn " Extra details:"
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for de in e.Data do
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let de = de :?> DictionaryEntry
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printfn $""" Key: {"'" + de.Key.ToString() + "'",-20} Value: {de.Value}"""
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printfn "\nException with some extra information..."
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runTest false
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printfn "\nException with all extra information..."
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runTest true
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// The example displays the following output:
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// Exception with some extra information...
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// An exception was thrown.
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// This statement is the original exception message.
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// Extra details:
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// Key: 'ExtraInfo' Value: Information from NestedRoutine1.
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// Key: 'MoreExtraInfo' Value: More information from NestedRoutine1.
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//
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// Exception with all extra information...
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// An exception was thrown.
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// This statement is the original exception message.
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// Extra details:
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// Key: 'stringInfo' Value: Information from NestedRoutine2.
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// Key: 'IntInfo' Value: -903
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// Key: 'DateTimeInfo' Value: 7/29/2013 10:50:13 AM
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// Key: 'ExtraInfo' Value: Information from NestedRoutine1.
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// Key: 'MoreExtraInfo' Value: More information from NestedRoutine1.
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//</snippet1>

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