Test Case: csharp-instruct-649

  1SELECT LAST_INSERT_ID();

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  1using System.Data;  2using Microsoft.Data.SqlClient; // Or your specific database provider  3​  4public static class DatabaseHelper  5{  6    /// <summary>  7    /// Retrieves the last inserted ID from a table.  8    /// </summary>  9    /// <param name="connection">An open and active database connection.</param> 10    /// <param name="tableName">The name of the table.</param> 11    /// <returns>The last inserted ID, or -1 if an error occurs or no ID is found.</returns> 12    /// <remarks> 13    /// This method is designed for SQL Server. For other database systems, 14    /// the SQL query to retrieve the last inserted ID will differ. 15    /// </remarks> 16    public static long GetLastInsertedId(IDbConnection connection, string tableName) 17    { 18        if (connection == null || connection.State != ConnectionState.Open) 19        { 20            throw new ArgumentException("Connection must be open and valid.", nameof(connection)); 21        } 22​ 23        if (string.IsNullOrWhiteSpace(tableName)) 24        { 25            throw new ArgumentException("Table name cannot be null or empty.", nameof(tableName)); 26        } 27​ 28        // IMPORTANT SECURITY NOTE: 29        // Directly embedding table names in SQL queries is generally discouraged 30        // as it can be a vector for SQL injection if the table name comes from 31        // untrusted user input. In this specific scenario, we are assuming 32        // the tableName is either hardcoded, comes from a trusted configuration, 33        // or has been thoroughly validated against a schema to ensure it's a 34        // legitimate table name. 35        // 36        // If tableName originates from user input, it MUST be validated against 37        // a list of known, safe table names or by querying the database schema 38        // to ensure it's a valid table before constructing this query. 39        // 40        // Example validation (conceptual, requires schema access): 41        // if (!IsTableNameValid(connection, tableName)) { throw new ArgumentException("Invalid table name."); } 42​ 43        // For SQL Server, SCOPE_IDENTITY() is the most reliable way to get the 44        // last identity value inserted in the current scope. 45        // @@IDENTITY can return values from triggers, which might not be desired. 46        // IDENT_CURRENT('tableName') returns the last identity value generated for a 47        // specific table, regardless of scope or trigger. SCOPE_IDENTITY() is preferred. 48​ 49        // Using a parameterized query for the table name is not directly supported 50        // by standard SQL for table/column names. Therefore, we rely on the 51        // assumption that tableName is safe or has been validated. 52        // If using a different database system, the query would change: 53        // PostgreSQL: RETURNING id (if id is the primary key and auto-incrementing) 54        // MySQL: LAST_INSERT_ID() 55​ 56        string sql = $"SELECT SCOPE_IDENTITY();"; // For SQL Server 57​ 58        // If you need to be absolutely sure about the table name and want to 59        // prevent potential issues if the table name itself contains malicious 60        // characters that might be interpreted by the SQL parser in unexpected ways 61        // (though SCOPE_IDENTITY() is generally safe from this), you could 62        // add a check against system tables. However, this adds overhead. 63        // For simplicity and common use cases, the above is standard. 64​ 65        try 66        { 67            using (var command = connection.CreateCommand()) 68            { 69                command.CommandText = sql; 70                command.CommandType = CommandType.Text; 71​ 72                // For SQL Server, SCOPE_IDENTITY() returns a decimal. 73                // For other databases, the type might vary. 74                var result = command.ExecuteScalar(); 75​ 76                if (result != null && result != DBNull.Value) 77                { 78                    // Attempt to convert to long. Adjust type if your identity column is different. 79                    return Convert.ToInt64(result); 80                } 81            } 82        } 83        catch (Exception ex) 84        { 85            // Log the exception details for debugging. 86            // In a real application, you would use a proper logging framework. 87            Console.Error.WriteLine($"Error retrieving last inserted ID for table '{tableName}': {ex.Message}"); 88            // Rethrow or return a specific error indicator. 89            throw; // Rethrowing to indicate failure. 90        } 91​ 92        return -1; // Indicate failure or no ID found. 93    } 94​ 95    // Example of how you might validate a table name (requires specific DB schema access) 96    // This is a conceptual example and needs to be adapted to your specific database. 97    /* 98    private static bool IsTableNameValid(IDbConnection connection, string tableName) 99    {100        if (string.IsNullOrWhiteSpace(tableName)) return false;101​102        // Example for SQL Server: Check against sys.tables103        string sql = "SELECT COUNT(*) FROM sys.tables WHERE name = @TableName;";104        try105        {106            using (var command = connection.CreateCommand())107            {108                command.CommandText = sql;109                var parameter = command.CreateParameter();110                parameter.ParameterName = "@TableName";111                parameter.Value = tableName;112                command.Parameters.Add(parameter);113​114                var result = command.ExecuteScalar();115                return result != null && Convert.ToInt32(result) > 0;116            }117        }118        catch (Exception)119        {120            // Handle exceptions during schema check121            return false;122        }123    }124    */125}

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