CODEWITHSUNDEEP
azure-api-management
Vowneee
Vowneee

Reputation: 1481

Azure APIM: Cannot Convert Object to String in Send-Request Policy

I’m trying to test backend connectivity in Azure API Management (APIM) using a send-request policy. I am trying in an automated solution for our developers to use an azuredevops pipeline where they can input the backend endpoint url to test the connectivity. I want to dynamically set the URL using a Named Value stored in APIM. We don’t have any way to test the network connectivity in the apim subnet as it’s a dedicated subnet and we would need this solution to check the connectivities enabled before creating the actual APIs.

However, I keep getting the error:

Cannot implicitly convert type 'object' to 'string'. An explicit conversion exists.

I used the following policy:

<!-- Send request to the backend URL -->
<send-request mode="new" response-variable-name="connectivityTest">
  <set-url>@(context.Variables["backendUrl"])</set-url>
  <set-method>GET</set-method>
</send-request>

<!-- Check response and return result -->
<choose>
  <when condition="@(context.Variables["connectivityTest"].StatusCode == 200)">
    <return-response>
      <set-status code="200" reason="OK" />
      <set-body>Backend is reachable</set-body>
    </return-response>
  </when>
  <otherwise>
    <return-response>
      <set-status code="502" reason="Bad Gateway" />
      <set-body>Backend is not reachable</set-body>
    </return-response>
  </otherwise>
</choose>

What I Have Tried: • I tried using .ToString() but still received the same error. • I verified that the Named Value testBackendUrl exists in APIM and has a valid string value. • I also tried using different ways of casting but no luck.

How do I correctly convert the Named Value to a string to use in the element? • Is there a better way to reference Named Values in APIM policies?

Environment: • Azure API Management • Named Value testBackendUrl is defined in APIM with a placeholder value like https://dummy.url.

Any help would be greatly appreciated!

Feel free to adjust the wording as needed before posting on Stack Overflow.

Upvotes: 0

Views: 45

Answers (1)

Kai Walter
Kai Walter

Reputation: 4041

I was able to get syntax accepted with

  • changing from context.Variables[] to the safer context.Variables.GetValueOrDefault<string>()
  • wrapping context.Variables["connectivityTest"] with IResponse
        <!-- Send request to the backend URL -->
        <send-request mode="new" response-variable-name="connectivityTest">
            <set-url>@(context.Variables.GetValueOrDefault<string>("backendUrl",""))</set-url>
            <set-method>GET</set-method>
        </send-request>
        <!-- Check response and return result -->
        <choose>
            <when condition="@(context.Variables.GetValueOrDefault<IResponse>("connectivityTest",null).StatusCode == 200)">
                <return-response>
                    <set-status code="200" reason="OK" />
                    <set-body>Backend is reachable</set-body>
                </return-response>
            </when>
            <otherwise>
                <return-response>
                    <set-status code="502" reason="Bad Gateway" />
                    <set-body>Backend is not reachable</set-body>
                </return-response>
            </otherwise>
        </choose>

I did not run/test the code, but it reflects what we use in many other parts of our APIM code base.

Upvotes: 1

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