Tuesday, November 24, 2015

WebAPI Headaches

WebAPI is great sometimes, and sometimes can cause you headaches.   I've found that using the format below as a starting point seems to resolve a lot of the problems.
  • Return an HTTPResponseMessage instead of a string.  Otherwise you will see an extra set of quotations around any string you return. 
  • Credentials should be pulled from the header instead of as a parameter on the method. 
  • Set the 'Content' property of the ResponseMessage to any string content you want to return.  If you want to return Json, set this value to 
  • Only use a single parameter on the methods you use. 
  • Use a DTO to pass more complex objects into a POST request. 

using System.Net
using System.Net.Http

 public IHttpActionResult MyMethod()  
     // check credentials  
     var user = Utility.AuthenticateUserFromHeader(Request.Headers);  
     if (user == null)  
         throw new HttpResponseException(Request.CreateResponse(HttpStatusCode.Unauthorized));  
     var data = Request.Content.ReadAsStringAsync().Result;  
     // process the data   
     return Ok("Response message");  

Dealing with CORS
Put the following in the Web.config to help with CORS.  (If you like this part, go upvote this guys answer: http://stackoverflow.com/a/36901271/224531)

    <add name="Access-Control-Allow-Origin" value="*" />
    <add name="Access-Control-Allow-Headers" value="Content-Type" />
    <add name="Access-Control-Allow-Methods" value="GET, POST, PUT, DELETE, OPTIONS" />
If you have some extra HEADER parameter, you must add it to Access-Control-Allow-Headers, like:
<add name="Access-Control-Allow-Headers" value="Content-Type, X-Your-Extra-Header-Key" />
And finally, to handle OPTIONS requests you must reply with empty response, adding in your application class:
protected void Application_BeginRequest()
    if (Request.Headers.AllKeys.Contains("Origin") && Request.HttpMethod == "OPTIONS")

Monday, November 23, 2015

See 'EntityValidationErrors' property for more details

This is an annoying error.  It generally occurs when calling SaveContext in EF.  It means that there was something wrong with the data you were trying to Save, but it's not going to tell you what exactly.  

Fortunately, there is an easy fix if you are running in the debugger.  To get EF to cough up the EntityValidationErrors, simply create a new watch with the following:


Wednesday, January 14, 2015

Git: Pulling in tags from remote

When working with a Git repository, you may find that you don't have the latest set of tags, or that a tag has moved, and your local repository does not reflect the update.   To update the tags in your local repository to reflect the remote, do the following:
git fetch --tags
This will pull down all tags on the current branch.