How do I make my kafka message value not return gibberish?

public static class Confluent
{
    public static void Consume()
    {
        var conf = new ConsumerConfig
        {
            GroupId = Guid.NewGuid().ToString(),
            BootstrapServers = "pdkafka.test.com:9092",//"localhost:9092",
            // Note: The AutoOffsetReset property determines the start offset in the event
            // there are not yet any committed offsets for the consumer group for the
            // topic/partitions of interest. By default, offsets are committed
            // automatically, so in this example, consumption will only start from the
            // earliest message in the topic 'my-topic' the first time you run the program.
            AutoCommitIntervalMs = 5000,
            AutoOffsetReset = AutoOffsetReset.Earliest,
            SecurityProtocol = SecurityProtocol.SaslPlaintext,
            SaslMechanism = SaslMechanism.Plain,
            SaslUsername= "test",
            SaslPassword= "123",

        };

        using (var c = new ConsumerBuilder<Ignore, string>(conf).Build())
        {
            c.Subscribe("prj.basedata");//c.Subscribe("test");//传入Topic Name

            CancellationTokenSource cts = new CancellationTokenSource();
            Console.CancelKeyPress += (_, e) =>
            {
                e.Cancel = true; // prevent the process from terminating.
                cts.Cancel();
            };

            try
            {
                while (true)
                {
                    try
                    {
                        var cr = c.Consume(cts.Token);
                        Console.WriteLine($"Consumed message '{cr.Value}' at: '{cr.TopicPartitionOffset}'.");
                    }
                    catch (ConsumeException e)
                    {
                        Console.WriteLine($"Error occured: {e.Error.Reason}");
                    }
                }
            }
            catch (OperationCanceledException)
            {
                // Ensure the consumer leaves the group cleanly and final offsets are committed.
                c.Close();
            }
        }
    }
}

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