Recently, while preparing my Logic App Data Mapper demos for the Nordic Integration Summit (NIS) 2025, I encountered this error while trying to test/execute a map inside the Data Mapper design tool:
Error message: correlationId=’2b6c1dfc-5c24-43d8-bd84-24b67dc5beb1′, operationName=’DataMapper.MapDeserializer.Deserialize’, message=’Map code error – either InvalidExpressionException or InvalidMapException‘, exception=’Microsoft.Azure.Workflows.DataMapper.ObjectModels.InvalidExpressionException: Expression could not be parsed. Invalid or unrecognized expression ‘concat(/ns0:PersonOrigin/FirstName, , /ns0:PersonOrigin/LastName)‘. Error details: ‘line 1:37 extraneous input ‘,’ expecting {Number, Boolean, NullValue, ‘*’, ‘.’, ‘..’, ‘@’, ‘$’, ‘/’, ‘(‘, DoubleQuotedLiteral, SingleQuotedLiteral, NCName}
at Microsoft.Azure.Workflows.DataMapper.Parser.ExpressionParser.Parse()
at Microsoft.Azure.Workflows.DataMapper.ObjectModels.Serialization.ExpressionTypeConverter.ReadMapCode(IParser parser)
at YamlDotNet.Serialization.ValueDeserializers.NodeValueDeserializer.DeserializeValue(IParser parser, Type expectedType, SerializerState state, IValueDeserializer nestedObjectDeserializer)’, organizationId=”, activityVector=’IN.00′, additionalProperties='{“ParentActivityId”:”00-a59f7a14bf0d23bc9731e3e906174980-c9b041b8b7d5b6e8-00″}’, extensionVersion=’1.138.54.0′, siteName=’UNDEFINED_SITE_NAME’, slotName=”, activityId=’2b6c1dfc-5c24-43d8-bd84-24b67dc5beb1′.
InvalidMapContent: An error occured while processing the map input: ‘Expression could not be parsed. Invalid or unrecognized expression ‘concat(/ns0:PersonOrigin/FirstName, , /ns0:PersonOrigin/LastName)’. Error details: ‘line 1:37 extraneous input ‘,’ expecting {Number, Boolean, NullValue, ‘*’, ‘.’, ‘..’, ‘@’, ‘$’, ‘/’, ‘(‘, DoubleQuotedLiteral, SingleQuotedLiteral, NCName}
📝 One-Minute Brief
In Data Mapper, an “InvalidExpressionException … unrecognized expression ‘concat’” often means a malformed parameter—e.g., an unquoted space between names: concat(/ns0:PersonOrigin/FirstName, , /ns0:PersonOrigin/LastName).
Fix: wrap the space in quotes—concat(/ns0:PersonOrigin/FirstName, " ", /ns0:PersonOrigin/LastName)—then save the map and re-test.
Cause
The error message could be clearer because the unrecognized expression “concat” is not entirely accurate, as it is an out-of-the-box function available in the Data Mapper. So, this error could only mean that something was wrong with the configuration of the concat function.
The Concat function combines two or more strings and returns the combined string.
In my case, I was trying to concatenate the first name with the last name; of course, in the middle, I need to add a static space to separate these two elements. But for some reason, I was able to set up a static value as a single space (without double quotes):
And that was the root cause of the problem, since we either set up:
- A custom string inside double quotes, like: ” “.
- Or we define a custom double/integer without double quotes like: 0.
Solution
The solution to fix this error, as you may already be guessing, is to set up that space inside double quotes:
Do not forget to save the map before you test it again.
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