C#、SQLServer - 阻止表行读取，根据需要进行编辑并释放锁

Question

I need to block database reads on row level while I'm executing update logic for same row. How would nice and clean solution look like? Here is some code I'm working on:

using (SqlConnection conn = new SqlConnection(Configuration.ConnectionString)) {
    conn.Open();
    using (SqlTransaction tran = conn.BeginTransaction(IsolationLevel.Serializable)) {
        //TODO lock table row with ID=primaryKey (block other reads and updates)
        using (SqlCommand cmd = new SqlCommand("SELECT Data FROM MyTable WHERE ID=@primaryKey", conn)) { 
            cmd.Parameters.AddWithValue("@primaryKey", primaryKey);
            using (var reader = cmd.ExecuteReader()) {
                data = PopulateData(reader);
            };
        }

        if (isUpdateNeeded(data)) {
            ChangeExternalSystemStateAndUpdateData(data) //EDIT - concurrent calls not allowed
            WriteUpdatesToDatabase(conn, tran, data);    //EDIT
            tran.Commit();
        }


    } //realease lock and allow other processes to read row with ID=primaryKey
}

EDIT:

I have following constraints:

• Code can be executed within different App pools simultaneously. So memory lock is not an option
• ChangeExternalSystemStateAndUpdateData() must be executed only once in the scope of the MyTable row. Concurrent calls will cause problems

Answer 1

Usually the problem here isn't so much row locking , but rather: other SPIDs acquiring read locks between your read and your update - which can lead to deadlock scenarios; the common fix here is to acquire a write lock in the initial read:

SELECT Data FROM MyTable WITH (UPDLOCK) WHERE ID=@primaryKey

Note that if another SPID is explicitly using NOLOCK then they'll still blitz past it.

You could also try adding ROWLOCK , ie WITH (UPDLOCK, ROWLOCK) - personally I'd keep it simple initially. Since you're in a serializable context, trying to be too granular may be a lost cause - key-range locks, etc.