HandyOrg/HandyControl · error · NotSupportedException

Can't call EndInit without first calling BeginInit.

Error message

Can't call EndInit without first calling BeginInit.

What it means

JumpList.EndInit finalizes ISupportInitialize by applying the list to the application (ApplyFromApplication), but only when _initializing is true, i.e. a matching BeginInit ran. Calling EndInit without BeginInit throws NotSupportedException "Can't call EndInit without first calling BeginInit."

Solutions

1. Always pair the calls: wrap population in try/finally so EndInit only runs after a successful BeginInit and is not called twice.
2. Track a bool _initialized flag in your code and only call EndInit when true.
3. If the list was populated without the BeginInit/EndInit pattern, call JumpList.ApplyFromApplication-equivalent flow correctly: BeginInit, mutate, EndInit once.
4. Create a new JumpList instance if initialization state is uncertain, rather than re-calling EndInit.

Example fix

// before
if (items.Count == 0) return; // BeginInit skipped
jumpList.EndInit(); // throws: no BeginInit

// after
jumpList.BeginInit();
try { foreach (var i in items) jumpList.JumpItems.Add(i); }
finally { jumpList.EndInit(); }

if (!beginInitCalled) return; // EndInit requires a prior BeginInit

try { jumpList.EndInit(); }
catch (NotSupportedException ex) { Log.Error(ex.Message); /* BeginInit was never called */ }

When it happens

Trigger: Calling EndInit() on a JumpList that never had BeginInit() called; calling EndInit() twice; a code path where an exception occurred between BeginInit and EndInit and EndInit is retried.

Common situations: Conditional code that skips BeginInit but unconditionally calls EndInit; duplicate initialization helpers both invoking EndInit; exception in the population code causing mismatched init pairs on retry.

Understand the failure class

Background: "Invalid state transition" errors: "status must be X, actually Y", "already rejected/charging/uninstalled", "cannot ... while running" — what they mean when a library rejects your call — this error's family across 31 libraries.

Related errors

• Calls to BeginInit cannot be nested.
• NotSupportedException
• NotSupportedException
• NotSupportedException
• NotSupportedException

AI-assisted analysis of HandyOrg/HandyControl@2c0875ebd6 (2026-09-14). Data as JSON: /api/errors/03e998313f0a3fe7. Report an issue: GitHub.

Appendix: source

Thrown at src/Shared/Microsoft.Windows.Shell/JumpList.cs:139

    }

    [SuppressMessage("Microsoft.Naming", "CA2204:Literals should be spelled correctly", MessageId = "BeginInit")]
    public void BeginInit()
    {
        if (!this._IsUnmodified)
        {
            throw new InvalidOperationException("Calls to BeginInit cannot be nested.");
        }
        this._initializing = new bool?(true);
    }

    [SuppressMessage("Microsoft.Naming", "CA2204:Literals should be spelled correctly", MessageId = "EndInit")]
    [SuppressMessage("Microsoft.Naming", "CA2204:Literals should be spelled correctly", MessageId = "BeginInit")]
    public void EndInit()
    {
        if (this._initializing != true)
        {
            throw new NotSupportedException("Can't call EndInit without first calling BeginInit.");
        }
        this._initializing = new bool?(false);
        this.ApplyFromApplication();
    }

    private static string _RuntimeId
    {
        get
        {
            string result;
            HRESULT hrLeft = NativeMethods.GetCurrentProcessExplicitAppUserModelID(out result);
            if (hrLeft == HRESULT.E_FAIL)
            {
                hrLeft = HRESULT.S_OK;
                result = null;
            }
            hrLeft.ThrowIfFailed();
            return result;

View on GitHub (pinned to 2c0875ebd6)