HandyOrg/HandyControl · error

Wrote an incorrect number of bytes

Error message

Wrote an incorrect number of bytes

What it means

Identical EFail throw inside HandyControl's InteropValues (the same IStream CopyTo logic embedded in the interop helper): when pstm.Write returns a count different from the bytes read, the stream wrapper declares the write failed and throws "Wrote an incorrect number of bytes". It guards against native IStream implementations that do not honor the COM contract of writing all requested bytes and reporting the count.

Solutions

1. Verify the native side correctly implements IStream.Write and returns the actual bytes written.
2. Ensure the COM stream's lifetime is managed correctly (release it only after copy completes; check Marshal.ReleaseComObject usage).
3. Retry the operation with a freshly obtained stream (re-copy clipboard data or re-open the storage).
4. Catch the failure in calling code and fall back to a managed stream path (e.g. copy via MemoryStream first).

// Validate the interop stream before use:
if (pstm == null) throw new InvalidOperationException("IStream is null");
// If obtainable, confirm STATSTG cbSize > 0 via IStream.Stat before copying.

static bool HasComStream(object comObj) =>
    comObj != null && Marshal.IsComObject(comObj);

try
{
    // interop copy path using InteropValues stream wrapper
}
catch (Exception ex) when (ex.Message == "Wrote an incorrect number of bytes")
{
    // re-fetch the stream source (e.g. re-read clipboard data) and retry once
}

When it happens

Trigger: Same as GPStream: CopyTo loop calls Read then pstm.Write; any Write return value != read (short write, 0, or an error HRESULT already converted) triggers the throw at the call site in InteropValues.cs:882.

Common situations: Using HandyControl interop helpers with clipboard/OLE streams (CF_HDROP / IStream from native code) where the native Write fails partway — often due to the source stream being released early, insufficient memory, or a custom IStream stub that returns the wrong count.

Understand the failure class

Background: "This is a bug, please report it": internal invariant violations, unreachable panics, and SNH errors explained — this error's family across 47 libraries.

Related errors

• Wrote an incorrect number of bytes
• ArgumentNullException
• NotImplemented
• IConnectionPoint::Advise returned an invalid cookie.

AI-assisted analysis of HandyOrg/HandyControl@2c0875ebd6 (2026-09-14). Data as JSON: /api/errors/17c77115c9784448. Report an issue: GitHub.

Appendix: source

Thrown at src/Shared/HandyControl_Shared/Tools/Interop/InteropValues.cs:882

        public virtual long CopyTo(IStream pstm, long cb, long[] pcbRead)
        {
            const int bufsize = 4096; // one page
            var buffer = Marshal.AllocHGlobal(bufsize);
            if (buffer == IntPtr.Zero) throw new OutOfMemoryException();
            long written = 0;

            try
            {
                while (written < cb)
                {
                    var toRead = bufsize;
                    if (written + toRead > cb) toRead = (int) (cb - written);
                    var read = Read(buffer, toRead);
                    if (read == 0) break;
                    if (pstm.Write(buffer, read) != read)
                    {
                        throw EFail("Wrote an incorrect number of bytes");
                    }
                    written += read;
                }
            }
            finally
            {
                Marshal.FreeHGlobal(buffer);
            }
            if (pcbRead != null && pcbRead.Length > 0)
            {
                pcbRead[0] = written;
            }

            return written;
        }

        public virtual Stream GetDataStream() => DataStream;

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