Access to modified closure in delegate

Question

I'm working with TaskCompletionSource. I register event on object, but when I try to unregister in my event method, resharper underlines it with note: Access to modified closure.

here is my code

var taskCompletionSource = new TaskCompletionSource<bool>();
OnConnectionStateChangedInd handlerConnectionStateChangedInd = null;
OnBootCompletedCnfCallback handlerBootCompletedCnfCallback = null;

handlerConnectionStateChangedInd = (id, method, addr, port, nick) =>
{
    _corePttObject.onConnectionStateChangedInd -= handlerConnectionStateChangedInd;
    _connectionState = id;

    taskCompletionSource.SetResult(true);
};
_corePttObject.onConnectionStateChangedInd += handlerConnectionStateChangedInd;

This line is underlined:

_corePttObject.onConnectionStateChangedInd -= handlerConnectionStateChangedInd;

Here is my complete definition of method:

public Task<LoginResult> LoginAsync(string address)
    {
        var taskCompletionSource = new TaskCompletionSource<LoginResult>();
        OnUserAcceptCertWithNamePasswInd handlerAcceptCertWithNamePasswInd = null;
        OnAppExLoginProtocolServiceCnf handlerAppExLoginProtocolServiceCnf = null;
        handlerAcceptCertWithNamePasswInd = (cert, caCert, rootCert, hash, pos, data) =>
        {
            var loginCompletedArgs = new LoginResult
            {
                SvrCertificate = ParseCertificate(cert),
                CaCertificate = ParseCertificate(caCert),
                RootCertificate = ParseCertificate(rootCert),
                CertificateHash = hash,
                GridPosition = pos,
                GridData = data
            };
            _corePttObject.onUserAcceptCertWithNamePasswInd -= handlerAcceptCertWithNamePasswInd;
            taskCompletionSource.SetResult(loginCompletedArgs);
        };

        handlerAppExLoginProtocolServiceCnf = (nick, result, cause, link) =>
        {
            _corePttObject.onAppExLoginProtocolServiceCnf -= handlerAppExLoginProtocolServiceCnf;
        };

        _corePttObject.onAppExLoginProtocolServiceCnf += handlerAppExLoginProtocolServiceCnf;
        _corePttObject.onUserAcceptCertWithNamePasswInd += handlerAcceptCertWithNamePasswInd;
        //TODO: read id.
        _corePttObject.Login(address, true, "ID");

        return taskCompletionSource.Task;
    }

score 1 · Answer 1 · edited May 23 '17 at 11:45

1

If you click click on the lightbulb suggestion, there will be an option "Why is ReSharper suggesting this". If you click on it, it will take you to this useful explanation.

I'd need more context to tell if this potential trap can actually hurt you in your particular case.

You can also check out this answer here.

edited May 23 '17 at 11:45

Community

1
1

answered Feb 19 '16 at 08:55

Gediminas Masaitis

3,172
14
35

score 1 · Accepted Answer · answered Feb 19 '16 at 09:11

1

The reason for this warning is: for handlerConnectionStateChangedInd you declare an anonymous method that - when eventually executed - will access/change _corePttObject.onConnectionStateChangedInd.

Then, after this declaration, you change _corePttObject.onConnectionStateChangedInd already in this line:

_corePttObject.onConnectionStateChangedInd += handlerConnectionStateChangedInd;

So ReSharper is warning you that the value _corePttObject.onConnectionStateChangedInd is different between the time you declare handlerConnectionStateChangedInd and the time it is executed.

answered Feb 19 '16 at 09:11

René Vogt

43,056
14
77
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So should I worry any problems? – JuP Feb 19 '16 at 09:25
@JurajP As long as you know what you are doing, there's no need to worry. And your code looks ok. – René Vogt Feb 19 '16 at 09:26

Access to modified closure in delegate

2 Answers2