Associate primarycontactid to Case-Dynamics CRM web API

I am trying to create a case and associate a contact in the primarycontactId field. I am using an alternate key to look up the contact as below.

POST https://xxxxx.crm.dynamics.com/api/data/v8.2/incidents HTTP/1.1
Accept: application/json
OData-MaxVersion: 4.0
OData-Version: 4.0
Content-Type: application/json; charset=utf-8
Host: xxxxxx.crm.dynamics.com
Content-Length: 161

{
  "title": "case101",
  "primarycontactid@odata.bind": "https://xxxxx.crm.dynamics.com/api/data/v8.2/contacts(xxi_xxx='2533274975913147')"
}

Code as below

using (HttpClient httpClient = new HttpClient())
            {
                var method2 = new HttpMethod("POST");
                Uri requesturi = new Uri(string.Format("{0}/api/data/v8.2/", url));
                httpClient.BaseAddress = requesturi;
                httpClient.Timeout = new TimeSpan(0, 0, 4);  // 10 minutes
                httpClient.DefaultRequestHeaders.Accept.Clear();
                httpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
                result = GetS2SAccessToken(url, pwd);
                httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", result);
                httpClient.DefaultRequestHeaders.Add("OData-MaxVersion", "4.0");
                httpClient.DefaultRequestHeaders.Add("OData-Version", "4.0");
                HttpRequestMessage request = new HttpRequestMessage(method,string.Format( "contacts(xxxxx_xxxx='{0}')",xxxx.ToString()));
                request.Content = new StringContent(props.ToString(), Encoding.UTF8, "application/json");
                HttpRequestMessage request2 = new HttpRequestMessage(method2, string.Format("incidents"));
                request2.Content = new StringContent(props1.ToString(), Encoding.UTF8, "application/json");

                HttpResponseMessage createResponse1;
                createResponse1 = await httpClient.SendAsync(request2);
                return createResponse1.Content;
         }

However I get:

An unexpected error occurred.","innererror":{ "message":"An unexpected error occurred.","type":"System.ServiceModel.FaultException.","type":"System.ServiceModel.FaultException1[[Microsoft.Xrm.Sdk.OrganizationServiceFault, Microsoft.Crm.Extensibility.OData.CrmODataServiceDataProvider.CreateEdmEntity(CrmODataExecutionContext context, String edmEntityName, EdmEntityObject entityObject, Boolean isUpsert)\r\n at Microsoft.Xrm.Sdk, Version=8.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35]]","stacktrace":" at Microsoft.Crm.Extensibility.OrganizationSdkServiceInternal.Create(Entity entity, CorrelationToken correlationToken, CallerOriginToken callerOriginToken, WebServiceType serviceType, Boolean checkAdminMode, Dictionary2 optionalParameters)\r\n at Microsoft.Crm.Extensibility.OData.CrmODataExecutionContext.Create(Entity entity)\r\n at Microsoft.Crm.Extensibility.OData.EntityController.PostEntitySet(String entitySetName, EdmEntityObject entityObject)\r\

Has anyone experienced this before?

Solution

You mixed up. Verify this & correct the schema name.

Incident has 2 optional contact lookups & schema name is primarycontactid & responsiblecontactid.

primarycontactid@odata.bind

But Incident has a mandatory Customer lookup & schema name is customerid. Without this Incident cannot be created. Pass this, request will succeed.

customerid_contact@odata.bind