Azure API Management- secure API through Client Ce

问题:

I am testing authenticate against Client Certificate functionality with out of the box Echo API Get request, I have added a inbound rule to check the request has certificate

I am using self signed certificate, I have updated it under CA and client certificates

 <inbound>
        <choose>
            <when condition="@(context.Request.Certificate == null)">
                <return-response>
                    <set-status code="403" reason="Invalid client certificate"/>
                </return-response>
            </when>
        </choose>
        <base />
 </inbound>

In my client Application, I am using below code to make a call

public static void MakeAnAzureApiCall()
        {

            var url = @"https://xxxx.azure-api.net/echo/resource?param1=sample";

            var handler = new WebRequestHandler();
            handler.ClientCertificateOptions = ClientCertificateOption.Manual;

            SecureString sec = new SecureString();
            string pwd = "P@ssw0rd"; 
            pwd.ToCharArray().ToList().ForEach(sec.AppendChar);
            sec.MakeReadOnly();

            var cert =  new X509Certificate2(@"C:\temp\apim.pfx", sec, X509KeyStorageFlags.MachineKeySet);
                //X509Certificate2.CreateFromCertFile(@"C:\temp\apim1.cer");

            handler.ClientCertificates.Add(cert);



            var client = new HttpClient(handler);
            var request = new HttpRequestMessage(HttpMethod.Get, url);


            request.Headers.TryAddWithoutValidation("Ocp-Apim-Subscription-Key", "xxxxxxxxxxxxxxxxxx");

            var response = client.SendAsync(request).Result;
            string responseString = response.Content.ReadAsStringAsync().Result;

        }

I am always getting 403 response from API management, looks like cert never received to APIM. Could any one know what I am doing wrong here?