Flow failing due to null values in json

[Anonymous]

 I am trying to consume message from my topics in Service bus and am successfully able to connect my Service bus to my flow but the response i get in the susequent compose step is as follows.

Unable to process template language expressions for action 'Apply_to_each' at line '1' and column '2299': 'The template language expression 'base64ToString(body('Get_messages_from_a_topic_subscription_(peek-lock)')?['ContentData'])' cannot be evaluated because property 'ContentData' cannot be selected. Array elements can only be selected using an integer index. Please see https://aka.ms/logicexpressions for usage details.'.

I figured out it is because of null value coming in my ContentData key for some of the values. I would like to know how should i handle this.

{
"ContentData": "asfgfhghdsdhgfYW50aGVyX01FOjI1OjE5Ljc2NjkzMzNaIn1d",
"ContentType": "text/plain",
"ContentTransferEncoding": "Base64",
"Properties": {
"$AzureWebJobsParentId": "0998cd2e-3349-4b9d-9d00-a11e5a9cfaa4",
"Diagnostic-Id": "00-0dfd49a0cb787642866d98c9ec0bae09-666048f718be0a4a-00",
"DeliveryCount": "2",
"EnqueuedSequenceNumber": "10309",
"EnqueuedTimeUtc": "2020-09-29T10:25:19Z",
"ExpiresAtUtc": "2020-10-13T10:25:19Z",
"LockedUntilUtc": "2020-09-30T08:45:00Z",
"LockToken": "67fe2da5-7d82-4c5a-b581-4b2e0eec4f45",
"MessageId": "3c2506bf54ed4f589d0bee0500316bde",
"ScheduledEnqueueTimeUtc": "0001-01-01T00:00:00Z",
"SequenceNumber": "4",
"Size": "1275",
"State": "Active",
"TimeToLive": "12096000000000"
},
"MessageId": "3c2506bf5sw2ssadsd500316bde",
"To": null,
"ReplyTo": null,
"ReplyToSessionId": null,
"Label": null,
"ScheduledEnqueueTimeUtc": "0001-01-01T00:00:00Z",
"SessionId": null,
"CorrelationId": null,
"SequenceNumber": 4,
"LockToken": "67fe2da5-7d82-4ghdhgd-0eec4f45",
"TimeToLive": "12096000000000"
},
{
"ContentData": null,
"ContentType": "text/plain",
"ContentTransferEncoding": "Base64",
"Properties": {
"$AzureWebJobsParentId": "aca8127e-4402-4e07-94db-fcfefa792d4f",
"Diagnostic-Id": "00-77c31c9b6f2a614a828992bfbe165844-c49ea39636564c4c-00",
"DeliveryCoun

[efialttes]

Hi!

I would add a Condition, so depending on your flow design it can be implemented by means of either an Action Block or an if() WDL based expression.

WDL expression on the left side of the condition rule:

empty(body('Get_messages_from_a_topic_subscription_(peek-lock)')?['ContentData'])

WDL expression on the right side of the condition rule:

false

Operator:

equals

Now, on the 'True branch' of the condition you can make your original WDL expression work:

base64ToString(body('Get_messages_from_a_topic_subscription_(peek-lock)')?['ContentData'])

Hope this helps

[Anonymous]

hi @efialttes ,

thanks for response, as i am new to power automate, would you please give me more details on the actions to be used. i have condition as an action but it asks for particular field to be evaluated. it will be much appreciated if  can you provide me some screenshots here. 
 my current flow looks like this:

[Anonymous]

hi @efialttes ,

I tried something, hopefully the same way as you said but i get this error:

Unable to process template language expressions for action 'Condition' at line '1' and column '2299': 'The template language expression 'empty(body('Get_messages_from_a_topic_subscription_(peek-lock)')?['ContentData'])' cannot be evaluated because property 'ContentData' cannot be selected. Array elements can only be selected using an integer index. Please see https://aka.ms/logicexpressions for usage details.'.

My flow looks something like this. please correct me if anything is wrong:

[efialttes · Accepted solution]

Thanx for the screenshot! Now I understand better the problem.

"Get messages from a topic subsciption" output is an array. This means you need to remive your current Condition action block, add an 'Apply to each', assign as its input "Get messages from a topic subsciption" output. Now, inside the 'Apply to each' you need to add your 'Condition' action block, assign the following WDL expression on the right side...

empty(item()?['ContentData'])

...assign the following WDL expression on the left side:

false

Please also note in your screenshot you typed false as regular text, not as an WDL expression

Then, on the true branch, 'Compose 3' action block I would add the following WDL expression:

base64ToString(item()?['ContentData'])

Please also note in your screenshot 'Compose 3' assigned value was added as regular text, not as an WDL expression. So it will fail unless you fix it

Hope this helps