Web api 2 completes successfully but returns server error 500

Question

I have created a controller using web api 2 in c#.

My controller method is a post and successfully completes, returning a 201

But when the client receives the response, a 500 internal server error is returned.

Can anyone advise why this is happening?

I thought that once a controller was returning a value, the request was complete, this is obviously not the case.

    [HttpPost]
    [Route("PostProperty/{agentId}")]
    public async Task<IActionResult> PostProperty(int agentId, [FromBody]CreatePropertyRequestDto value)
    {
        string result = await _mediator.Send(new NewPropertyRequest() { NewProperty = value, AgentId = agentId });
        var c = CreatedAtRoute("getproperties", new { agentId, propertyIds = result }, result);
        return c;
    }

If I look in the output window I can see a 500 is being thrown, but I still don't know where or why. Please help

Application Insights Telemetry (unconfigured): {
    "name": "Microsoft.ApplicationInsights.Dev.Request",
    "time": "2018-08-13T20:51:39.9717971Z",
    "tags": {
        "ai.operation.name": "POST Properties/PostProperty [agentId]",
        "ai.cloud.roleInstance": "DESKTOP-DM70VVS",
        "ai.location.ip": "127.0.0.1",
        "ai.application.ver": "1.0.0.0",
        "ai.operation.id": "4d86444a-4e214be6ea456695",
        "ai.internal.nodeName": "DESKTOP-DM70VVS",
        "ai.internal.sdkVersion": "aspnet5c:2.1.1"
    },
    "data": {
        "baseType": "RequestData",
        "baseData": {
            "ver": 2,
            "id": "|4d86444a-4e214be6ea456695.",
            "name": "POST Properties/PostProperty [agentId]",
            "duration": "00:00:02.7187869",
            "success": false,
            "responseCode": "500",
            "url": "http://localhost:63103/api/properties/PostProperty/1",
            "properties": {
                "httpMethod": "POST",
                "AspNetCoreEnvironment": "Development",
                "DeveloperMode": "true"
            }
        }
    }
}

EDIT:

If I return an OK(result) a 200 is returned. So I can now confirm CreatedAtRoute() is the culprit. I have enabled app.UseDeveloperExceptionPage(); in Startup.cs and the showed me a helpful message

InvalidOperationException: No route matches the supplied values.

Reading this thread I can see the I must match the parameters of the action I am saying the item was created at.

updated post action

    [HttpPost]
    [Route("PostProperty/{agentId}")]
    public async Task<IActionResult> PostProperty(int agentId, [FromBody]CreatePropertyRequestDto value)
    {
        string result = await _mediator.Send(new NewPropertyRequest() { NewProperty = value, AgentId = agentId });
        return CreatedAtRoute($"GetProperty", new { agentId = agentId, propertyId = result });
    }

action the above is referencing

    [HttpGet]
    [Route("GetProperty/{agentId}/{propertyId}")]
    public async Task<IActionResult> GetProperty(int agentId, string propertyId)
    {
        if (agentId <= 0 || propertyId == null)
        {
            return BadRequest("agentId or propertyId was invalid. agentId must be a valid id and propertyId cannot be null");
        }

        IEnumerable<PropertyDto> properties = await GetPropertiesRequest(agentId, new List<string>(){ propertyId });
        PropertyDto property = properties.FirstOrDefault();
        if (property == null)
        {
            return NotFound();
        }
        return Ok(property);
    }

even with the update to my post action I still get

InvalidOperationException: No route matches the supplied values.

below also returns the same exception

CreatedAtRoute(routeName: "GetProperty", routeValues: new { agentId = agentId, propertyId = result }, value: result);

Answer 1

I resolved my Issue by using CreatedAtAction(). In this scenario it is more suited that CreatedAtRoute as it is in the same controller. For a more detailed explanation of the differences read this thread

CreatedAtAction($"GetProperty", new { agentId = agentId, propertyId = result }, result);