F#单例和内部资源处理

module SingletonExample =
    let private instance = new MyClass()
    let getInstance() = instance

and MyClass() =
    member this.DoSomething() =
        printfn "Doing something..."

let instance = SingletonExample.getInstance()
instance.DoSomething()

open System
open System.IO

let processFile filePath =
    use fileStream = new FileStream(filePath, FileMode.Open)
    use reader = new StreamReader(fileStream)
    let content = reader.ReadToEnd()
    printfn "%s" content

let private instance = Lazy<MyClass>.Create(() => new MyClass())
let getInstance() = instance.Value

let processFile filePath =
    let fileStream = new FileStream(filePath, FileMode.Open)
    try
        let reader = new StreamReader(fileStream)
        try
            let content = reader.ReadToEnd()
            printfn "%s" content
        finally
            reader.Dispose()
    finally
        fileStream.Dispose()