Question

我试图捕获异常，但编译器发出警告：此类型测试或向下转换将始终保持

let testFail () =
    try
        printfn "Ready for failing..."
        failwith "Fails"
    with
    | :? System.ArgumentException -> ()
    | :? System.Exception -> ()

问题是：如何在没有警告的情况下这样做？（我相信必须有办法做到这一点，否则应该没有警告）

喜欢C＃

try
{
    Console.WriteLine("Ready for failing...");
    throw new Exception("Fails");
}
catch (Exception)
{
}

Answer 1

C＃：

void testFail()
{
    try
    {
        Console.WriteLine("Ready for failing...");
        throw new Exception("Fails");
    }
    catch (ArgumentException)
    {
    }
    catch
    {
    }
}

F＃等价物：

let testFail () =
    try
        printfn "Ready for failing..."
        failwith "Fails"
    with
    | :? System.ArgumentException -> ()
    | _ -> ()

C＃：

void testFail()
{
    try
    {
        Console.WriteLine("Ready for failing...");
        throw new Exception("Fails");
    }
    catch (ArgumentException ex)
    {
    }
    catch (Exception ex)
    {
    }
}

F＃等价物：

let testFail () =
    try
        printfn "Ready for failing..."
        failwith "Fails"
    with
    | :? System.ArgumentException as ex -> ()
    | ex -> ()

C＃：

void testFail()
{
    try
    {
        Console.WriteLine("Ready for failing...");
        throw new Exception("Fails");
    }
    catch
    {
    }
}

F＃等价物：

let testFail () =
    try
        printfn "Ready for failing..."
        failwith "Fails"
    with
    | _ -> ()

正如Joel所说，您不希望在C＃中使用catch (Exception)，原因与您在F＃中不使用| :? System.Exception ->的原因相同。

Answer 2

try 
  .. code ..
with
  | _ as e ->

如何在F＃中没有警告的情况下捕获任何异常（System.Exception）？

2 个答案: