Publish a json message to AWS SNS topic using C# - amazon-web-services

Question

I Am trying to publish a Json Message to AWS SNS topic from my C# Application using AWS SDk. Its [enter image description here][1]populating message in string format and message attribute filed is not populated.
Code sample is as below:
var snsClient = new AmazonSimpleNotificationServiceClient(accessId, secretrkey, RegionEndpoint.USEast1);
PublishRequest publishReq = new PublishRequest()
{
TargetArn = topicARN,
MessageStructure = "json",
Message = JsonConvert.SerializeObject(message)
};
var msgAttributes = new Dictionary<string, MessageAttributeValue>();
var msgAttribute = new MessageAttributeValue();
msgAttribute.DataType = "String";
msgAttribute.StringValue = "123";
msgAttributes.Add("Objectcd", msgAttribute);
publishReq.MessageAttributes = msgAttributes;
PublishResponse response = snsClient.Publish(publishReq);

Answer 1

Older question but answering as I came across when dealing with similar issue
When you set the MessageStructure to "json".
The json must contain at least a top-level JSON key of "default" with a value that is a string.
So json needs to look like
{
"default" : "my message"
}
My solution looks something like
var messageDict = new Dictionary<string,object>()
messageDict["default"] = "my message";
PublishRequest publishReq = new PublishRequest()
{
TargetArn = topicARN,
MessageStructure = "json",
Message = JsonConvert.SerializeObject(messageDict)
};
// if json is an object
// then
messageDict["default"] = JsonConvert.SerializeObject(myMessageObject);
I'm am using PublishAsync on v3
From the documentation
https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SNS/TPublishRequest.html
Message structure
Gets and sets the property MessageStructure.
Set MessageStructure to json if you want to send a different message for each protocol. For example, using one publish action, you can send a short message to your SMS subscribers and a longer message to your email subscribers. If you set MessageStructure to json, the value of the Message parameter must:
be a syntactically valid JSON object; and
contain at least a top-level JSON key of "default" with a value that is a string.
You can define other top-level keys that define the message you want to send to a specific transport protocol (e.g., "http").
Valid value: json

Answer 2

Great coincidence!
I was just busy writing a C# implementation to publish a message to SNS when I stumbled up on this post. Hopefully this helps you.
The messageBody argument we pass down to PublishMessageAsync is a string, it can be deserialized JSON for example.
public class SnsClient : ISnsClient
{
private readonly IAmazonSimpleNotificationService _snsClient;
private readonly SnsOptions _snsOptions; // You can inject any options you want here.
public SnsClient(IOptions<SnsOptions> snsOptions, // I'm using the IOptionsPattern as I have the TopicARN defined in the appsettings.json
IAmazonSimpleNotificationService snsClient)
{
_snsOptions = snsOptions.Value;
_snsClient = snsClient;
}
public async Task<PublishResponse> PublishMessageAsync(string messageBody)
{
return await _snsClient.PublishAsync(new PublishRequest
{
TopicArn = _snsOptions.TopicArn,
Message = messageBody
});
}
}
Also note the above setup uses Dependency Injection, so it would require you to set up an ISnsClient and you register an instance when bootstrapping the application, something as following:
services.TryAddSingleton<ISnsClient, SnsClient>();