不使用 catch 块捕获的异常。 为什么？

Question

So I have made use of a few try/catch blocks during my first project learning C#. For the most part, they have worked fine. However, there are a couple where the code still breaks at the point of an exception despite the fact it is finding the exact exception type I was anticipating and hoping for. I'll provide an example of code where this issue occurs.

Here is where I try to catch the exception:

app.MoveFolder(input1, input2);

try {
    //code here
} catch (ArgumentException) {
    //code here
}
break;

Here is the function where I create the exception:

public void MoveFolder(string folderPath, string newLocation) {
    this.ThrowExceptionIfFolderDoesntExist(folderPath);

    if (Directory.Exists(newLocation) == true) {
        throw new ArgumentException("example");
    }
    Directory.Move(folderPath, newLocation);
}

The ThrowExceptionIfFolderDoesntExist() function leads to this:

private void ThrowExceptionIfFolderDoesntExist(string folderPath) {
    if (this.CheckFolderExists(folderPath) == false) {
        throw new ArgumentException("This folder does not exist");
    }
}

So, as you can see, both this and the if statement in my MoveFolder() function should return ArgumentExceptions which I was hoping to catch. In the case of the latter function, this works as intended. However, if I try to move a folder to a location that already exists, then I get the following:

Unhandled Exception: System.ArgumentException: example

This is not what I'm wanting, as I want the catch block to handle this particular ArgumentException also. Is this something to do with the catch block thinking I am referring to a specific argument exception? I would have thought it would refer to all ArgumentExceptions.

How can I resolve this?

Answer 1

In order to do a proper try/catch, you need to do the following:

1. Place your method in the try block
2. catch the Exception(s)
3. throw the Exception

Here is some code

try
{
    app.MoveFolder(input1, input2);
}
// catch ArgumentException
catch(ArgumentException ex)
{
    throw;
}
// catch all others
catch(Exception ex)
{
    throw;
}

Answer 2

In order to catch an exception thrown by a function, the function needs to be called in the Try {}. You can do as the others said and call the MoveFolder inside a Try Block. If you throw an exception outside of the Try Block, it can sometimes be picked up by other catch blocks, or just unhandled and creates an error.

try {
    app.MoveFolder(Something1, Something2);
} catch (ArgumentException ex) {
    //Do something with Exception
}