How to use a variable when returning response in policy definition?

Question

I'm configuring inbound policies in an instance of Azure API Management.

First, I set a variable:

<set-variable name="var1" value="" />

Then I send a request

<send-request mode="new" response-variable-name="var1" timeout="20" ignore-error="false">

Which returns a JSON. When testing I get the following message in trace tab:

GET request to 'https://my-api.azure-api.net/api/data' has been sent, result stored in 'var1' variable.

I guess the send-request policy works and the result is stored in the variable. Then I want to return a response (still in inbound, I get 500 when trying to do it in outbound):

<return-response response-variable-name="existing response variable">
    <set-status code="200" reason="OK" />
    <set-header name="Content-Type" exists-action="override">
        <value>application/json</value>
    </set-header>
    <set-body>
    {
        "success": true,
        "var1": context.Variables["var1"]
    }
    </set-body>
</return-response>

My problem is it doesn't work... It just renders context.Variables["var1"].

And so does:

• @context.Variables["var1"]
• @{ context.Variables.GetValueOrDefault<string>("var1") }
• @context.Variables.GetValueOrDefault("var1")

All of them are rendered as written, no value is being extracted.

Edit: I also tried adding a placeholder string and then using

<find-and-replace from="Placeholder" to="context.Variables.GetValueOrDefault("var1")" />

And try to place it in inbound and outbound alike. But this policy did not launch.

It's a JSON object that I want to append to the response (small detail: in reality I have this issue with multiple variables).

My question is: how can I add my declared variable to the response?

Answer 1

There are two ways you can go about this. You could to use policy expressions for that: https://learn.microsoft.com/en-us/azure/api-management/api-management-policy-expressions. The thing to remember is that they can only be used to construct whole value for policy, not part of it, so:

<set-body>@("{\"success\": true, \"var1\": " + ((IResponse)context.Variables["var1"]).Body.As<string>() + "}"</set-body>

Or with set-body policy you could use liquid template:

<set-variable name="var1body" value="@((IResponse)context.Variables["var1"]).Body.As<string>())" />
<set-body template="liquid">
{
    "success": true,
    "var1": {{context.Variables["var1body"]}}
}
</set-body>