jstedfast/MailKit · error · InvalidOperationException

No hash value computed.

Error message

No hash value computed.

What it means

MD4.Hash throws InvalidOperationException('No hash value computed.') when the Hash property is read before any data has been hashed, because hashValue is still null. MailKit's NTLM MD4 lazily stores the digest only after ComputeHash/TransformFinalBlock completes.

Solutions

1. Call ComputeHash(...) (or TransformFinalBlock) before reading Hash
2. For incremental hashing, always finish with TransformFinalBlock
3. Check hashValue availability or wrap Hash access in try-catch for InvalidOperationException

Example fix

// before
var md4 = new MD4 ();
md4.TransformBlock (data, 0, data.Length, null, 0);
byte[] h = md4.Hash; // InvalidOperationException
// after
var md4 = new MD4 ();
md4.TransformBlock (data, 0, data.Length, null, 0);
md4.TransformFinalBlock (Array.Empty<byte> (), 0, 0);
byte[] h = md4.Hash;

// only read Hash after a hash operation completed:
// md4.ComputeHash(data) or md4.TransformFinalBlock(...) must have been called

static bool HasDigest (Func<byte[]?> hashAccessor) => hashAccessor () != null;

byte[] digest;
try {
    digest = md4.Hash;
} catch (InvalidOperationException) {
    digest = md4.ComputeHash (Array.Empty<byte> ());
}

When it happens

Trigger: Accessing md4.Hash immediately after construction, or after TransformBlock-only usage where TransformFinalBlock was never called.

Common situations: Debug/inspection code reading Hash mid-pipeline; incremental hashing that forgot the final TransformFinalBlock call; error paths that abandon hashing then read Hash.

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

• HashAlgorithm
• buffer
• The HeaderSet is read-only.
• negotiate
• challenge

AI-assisted analysis of jstedfast/MailKit@9d3859a785 (2026-09-15). Data as JSON: /api/errors/3d3dfc65e0bdfe78. Report an issue: GitHub.

Appendix: source

Thrown at MailKit/Security/Ntlm/MD4.cs:79

			state = new uint[4];
			count = new uint[2];

			// temporary buffer in MD4Transform that we don't want to allocate on each iteration
			x = new uint[16];

			// the initialize our context
			Initialize ();
		}

		~MD4 ()
		{
			Dispose (false);
		}

		public byte[] Hash {
			get {
				if (hashValue == null)
					throw new InvalidOperationException ("No hash value computed.");

				return hashValue;
			}
		}

		void HashCore (byte[] block, int offset, int size)
		{
			// Compute number of bytes mod 64
			int index = (int) ((count[0] >> 3) & 0x3F);

			// Update number of bits
			count[0] += (uint) (size << 3);
			if (count[0] < (size << 3))
				count[1]++;

			count[1] += (uint) (size >> 29);

			int partLen = 64 - index;

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