c# - Posting from AWS-API Gateway to Lambda -

i have simple c# aws lambda function succeeds test lambda console test fails 502 (bad gateway) if called api gateway (which generated lambda trigger option) , if use postman.(this initial function has open access (no security))

// request header     content-type: application/json  //  request body     {         "userid":22,         "files":["file1","file2","file3","file4"]     } 

the error in logs is:

wed feb 08 14:14:54 utc 2017 : endpoint response body before transformations: {   "errortype": "nullreferenceexception",   "errormessage": "object reference not set instance of object.",   "stacktrace": [     "at blahblahmynamespace.function.functionhandler(ziprequest input, ilambdacontext context)",     "at lambda_method(closure , stream , stream , contextinfo )"   ] } 

it seems posted object not being passed lambda input argument.

code below

// lambda function      public lambdaresponse functionhandler(ziprequest input, ilambdacontext context)         {             try             {                 var logger = context.logger;                 var headers = new dictionary<string, string>();                  if (input == null || input.files.count == 0)                 {                     logger.logline($"input null");                     headers.add("testheader", "ohdear");                     return new lambdaresponse { body = "fail", headers = headers, statuscode = httpstatuscode.badrequest };                 }                 else                 {                     logger.logline($"recieved request user{input?.userid}");                     logger.logline($"recieved {input?.files?.count} items zip");                     headers.add("testheader", "yeah");                     return new lambdaresponse { body = "hurrah", headers = headers, statuscode = httpstatuscode.ok };                 }             }             catch (exception ex)             {                 throw ex;             }         } 

//lambda response/ziprequest class

public class lambdaresponse {      public httpstatuscode statuscode { get; set; }     public dictionary<string, string> headers { get; set; }     public string body { get; set; } } public class ziprequest {     public int userid { get; set; }     public ilist<string> files { get; set; } } 

when using lambda proxy integration in api gateway, first parameter functionhandler not body of post, api gateway-created object, let's call lambdarequest. try these changes sample code. add:

public class lambdarequest {    public string body { get; set; } } 

change handler prototype to:

public lambdaresponse functionhandler(lambdarequest req, ilambdacontext context) 

and inside functionhandler add:

ziprequest input = jsonconvert.deserializeobject<ziprequest>(req.body); 

the full lambdarequest object documented under input format of lambda function proxy integration in aws docs, , contains http headers, http method, query string, body, , few other things.