如何解决 IEnumerator GetEnumerator C# 的问题

Question

i have start to code C# and i have a little problem with my application, it's show me the error code:

CS1674 WPF C# 'IEnumerator': type used in a using statement must be implicitly convertible to 'System.IDisposable' or implement a suitable 'Dispose' method.

I don't know how to fix that.

My code is:

    using (IEnumerator enumerator = this.listViewBoxes.Items.GetEnumerator())
                        {
                            while (enumerator.MoveNext())
                            {
                                object obj = enumerator.Current;
                                ListViewItem listViewItem = (ListViewItem)obj;
                                int num5 = 0;
                                int num6 = 0;
                                try
                                {
                                    if (listViewItem.Tag.ToString() == "HEAD")
                                    {
                                        num5 = this.displayBox.Width / 2;
                                        num6 = num + int.Parse(this.offsetHead.Text) * 5;
                                    }
                                    else if (listViewItem.Tag.ToString() == "BODY")
                                    {
                                        num5 = this.displayBox.Width / 2;
                                        num6 = num + int.Parse(this.offsetBody.Text) * 5;
                                    }
                                    else if (listViewItem.Tag.ToString() == "ARM0")
                                    {
                                        num5 = this.displayBox.Width / 2 - 25;
                                        num6 = num2 + int.Parse(this.offsetArms.Text) * 5;
                                    }
                                    else if (listViewItem.Tag.ToString() == "ARM1")
                                    {
                                        num5 = this.displayBox.Width / 2 + 25;
                                        num6 = num2 + int.Parse(this.offsetArms.Text) * 5;
                                    }
                                    else if (listViewItem.Tag.ToString() == "LEG0")
                                    {
                                        num5 = this.displayBox.Width / 2 - 10;
                                        num6 = num3 + int.Parse(this.offsetLegs.Text) * 5;
                                    }
                                    else if (listViewItem.Tag.ToString() == "LEG1")
                                    {
                                        num5 = this.displayBox.Width / 2 + 10;
                                        num6 = num3 + int.Parse(this.offsetLegs.Text) * 5;
                                    }

If you need the full code, i can give you on a pastebin or something else thanks !!

Answer 1

Is because the non generic IEnumerator does not implement IDisposable . Just remove the using .

var enumerator = this.listViewBoxes.Items.GetEnumerator();

Answer 2

IEnumerator 不继承 IDispoable，因此它不能与 using 语句一起使用。

Answer 3

Yeah this whole thing should be re-written entirely and I would certainly recommend using a foreach loop here as well.

Also I see nothing calling on the Dispose() method from IDisposable but if you need to add it from what I can see here at least I would say try creating a local variable and casting your enumerator object to IDisposable like so:

IDisposable disposable = (IDisposable)enumerator;

//example of calling Dispose()

disposable?.Dispose();

Note the ?. operator. It is important to check for null here and in this example we're using null propagation since there is a chance that enumerator object instance does not implement IDisposable .

You may even want to surround the last statement in a try-catch loop similar to this:

try
{
    disposable?.Dispose();
}

catch (NullreferenceException ex)
{
   // insert logic to handle null references in here.
}

If that doesn't help I'll need a little more elaboration.

Answer 4

As some have pointed out, IEnumerable doesn't implement IDisposable, and it would probably be a good idea to use foreach instead.

Information on foreach: https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/foreach-in

I, personally would also use a switch-statement instead of your if-else chain.

So with those changes the code would look something like this:

foreach (ListViewItem listViewItem in this.listViewBoxes.Items)
{
    int num5 = 0;
    int num6 = 0;
    try
    {
        switch (listViewItem.Tag.ToString())
        {
            case "HEAD":
                num5 = this.displayBox.Width / 2;
                num6 = num + int.Parse(this.offsetHead.Text) * 5;
                break;    
            case "BODY":
                num5 = this.displayBox.Width / 2;
                num6 = num + int.Parse(this.offsetBody.Text) * 5;
                break;    
            case "ARM0":
                num5 = this.displayBox.Width / 2 - 25;
                num6 = num2 + int.Parse(this.offsetArms.Text) * 5;
                break;    
            case "ARM1":
                num5 = this.displayBox.Width / 2 + 25;
                num6 = num2 + int.Parse(this.offsetArms.Text) * 5;
                break;    
            case "LEG0":
                num5 = this.displayBox.Width / 2 - 10;
                num6 = num3 + int.Parse(this.offsetLegs.Text) * 5;
                break;    
            case "LEG1":
                num5 = this.displayBox.Width / 2 + 10;
                num6 = num3 + int.Parse(this.offsetLegs.Text) * 5;
                break;
        }
    }
    catch (Exception e)
    {
        //Exception handling
    }
}