[HOW TO FIX] Azure APIM using context.User.Email causing request to fail

Question

I want to add a the email id of the user in the header of the request which is being send from API Management service.

I have added the following policy in the inbound processing.

<set-header name="user" exists-action="override">   
         <value>@{var usr = context.User; return usr.Email;}</value> 
 </set-header>

Getting the following error in the trace

{     "messages": [
         {        
    	 "message": "Expression evaluation failed.",
       	"expression": "var usr = context.User; return usr.Email;",
		"details": "Object reference not set to an instance of an object." 
       	},

 		"Expression evaluation failed. Object reference not set to an instance of an object.", 
	"Object reference not set to an instance of an object." 
 		 ] 
}

I have tired another way also

<set-header name="user" exists-action="override">
            <value>@(context.User.Email)</value>
 </set-header>

Getting the following error in the trace

{
    "messages": [
        {
            "message": "Expression evaluation failed.",
            "expression": "context.User.Email",
            "details": "Object reference not set to an instance of an object."
        },
        "Expression evaluation failed. Object reference not set to an instance of an object.",
        "Object reference not set to an instance of an object."
    ]
}

Answer 1

Manuprasad M N Thanks for posting your question in Microsoft Q&A. Based on the expression evaluation, it appears that context.User is null, and this might occur if the subscription key used in the request didn't have userId. Are you observing this error from Azure Portal Test console? If so, it uses built-in all-access subscription which doesn't have user info.

You can test with a subscription key which has user info mapped (like All APIs in the screenshot above) by passing it in the header like below and should provide the result.

Also, I would suggest checking context.User as null to avoid null reference exception. I hope this helps and let me know if any questions.

set-header name="user" exists-action="override">
            <value>@(context.User?.Email)</value>
</set-header>

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