[electricessence]

ExecuteScalar<T> and ExecuteScalarAsync<T> convert the way Map<T>() does, so a port that keeps the same T no longer fails only on a real database.

The problem

• ExecuteScalar<T> cast the value exactly and threw InvalidCastException when the column type differed from T: a bigint serial read as int, or a numeric identity read as long. A single-value Map<T>() converts, and so does Dapper.

What changes

• ExecuteScalar<T>(), ExecuteScalarAsync<T>(), ExecuteReturn<T>() and ExecuteReturnAsync<T>() use the single-value conversion Map<T>() uses:
  • a value that is already a T is returned as is;
  • NULL, DBNull and no row give default(T), as before;
  • anything else is converted with the same range check: a bigint into int, a numeric into long, an int into long. A value out of range throws ValueMappingException with the OverflowException inside, the same as Map<int>().
• The conversion happens after the command has finished, so the connection is released first, as before. Nothing is cast any more, so no exact-cast variant is kept.
• The Func<object?, T> transform overloads are unchanged. No public signature changes, so PublicAPI.Unshipped.txt is untouched.

Behavior change

• Calls that threw InvalidCastException now convert, or throw ValueMappingException on overflow. Noted in whats-new-11.md.

Tests

• A new matrix of about 100 value and target pairs compares each scalar with Map<T>() over a typed reader (the same value, or the same failure type and message), sync and async.
• Named cases: bigint into int, numeric into long, int into long, overflow, NULL and no row, a failed conversion leaving the connection as it was found, cancellation.
• A compiled sample reads a bigint as int; the old "failed cast" check in the samples is replaced by three checks.

Checks

• Release and Debug builds: 0 warnings, 0 errors. Tests: Debug 9696 of 9696. Release 9696 of 9696 on the third run; the first two Release runs each failed one of two known flaky tests that this change does not touch (TokenTerminalTests.Allocation_Channel, then a LeakPipelineTests Channel case), which are being fixed separately. Samples: 105 of 105 checks pass. Style and analyzers: 0 findings. DocFX: 0 warnings.

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