Category Archives: ASP.NET

Dynamic Robots.txt with Web Api 2

Hi everyone,

For a project I’m currently working on I needed a dynamic robots.txt. Because our test environment is public facing we want to keep it from being indexed by Google etc. It took a bit of Googling to find a solution that worked, but in the end it was actually pretty simple.

Here’s the action in one of the API Controllers:

    public class UtilitiesController : CustomBaseApiController
    {
        [Route("Robots.txt")]
        [HttpGet]
        public HttpResponseMessage GetRobotsFile()
        {
            var resp = new HttpResponseMessage(HttpStatusCode.OK);
            var stringBuilder = new StringBuilder();
 
            if (Helpers.IsProduction())
            {
                // Allow bots in production
                stringBuilder.AppendLine("user-agent: *");
                stringBuilder.AppendLine("disallow: ");
            }
            else
            {
                // Don't allow bots in non-production environments
                stringBuilder.AppendLine("user-agent: *");
                stringBuilder.AppendLine("disallow: *");
            }
 
            resp.Content = new StringContent(stringBuilder.ToString());
 
            return resp;
        }
    }

Also need to add the following to your web.config so that the robots.txt file can processed by the routing handler. Without this IIS will attempt to serve it as a static file and will return a 404 when it’s not found:

<system.webServer>
    <modules>
    <!-- ... -->
        <handlers>
        <add name="RobotsTxt" path="robots.txt" verb="GET" type="System.Web.Handlers.TransferRequestHandler" preCondition="integratedMode,runtimeVersionv4.0" />
        <!-- Other handlers -->
    </modules>
    <!-- ... -->
</system.webServer>

In production you’ll end up with the following:

user-agent: *
disallow:

And any other environments:

user-agent: *
disallow: *

Thanks to these answers on stackoverflow for the info:
https://stackoverflow.com/a/52270877/522859
https://stackoverflow.com/a/17037935/522859

LINQ to Entities does not recognize the method ‘System.Linq.IQueryable

Hi everyone,

I ran into the following error today while attempting to use a raw query with entity framework:

LINQ to Entities does not recognize the method ‘System.Linq.IQueryable…method, and this method cannot be translated into a store expression

I was using FromQuery, and while I’m not too sure what was causing the issue, switching to SqlQuery resolved it:

// Original code
var carList = resp.Db.Cars.FromSql(“SELECT * FROM cars”);
// Changed code
var carList = resp.Db.Cars.SqlQuery(“SELECT * FROM cars”);

Hopefully that’s able to help out anyone else with the issue.

Thanks,
Chris

Web API 2 – ExceptionMessage=No MediaTypeFormatter is available to read an object of type ‘HttpPostedFileBase’ from content with media type ‘multipart/form-data’.

Hi everyone,

I ran into the following error while trying to get image uploads working with Web API 2:

ExceptionMessage=No MediaTypeFormatter is available to read an object of type ‘HttpPostedFileBase’ from content with media type ‘multipart/form-data’.

I had been trying to copy the following from an mvc controller in another project:

public IHttpActionResult Upload(HttpPostedFileBase file, Models.Image.ImageAssociationType associationType, int associationId)

The fix was to use the following instead:

public IHttpActionResult Upload(Models.Image.ImageAssociationType associationType, int associationId)
{
var file = HttpContext.Current.Request.Files.Count > 0 ? HttpContext.Current.Request.Files[0] : null;

Thanks to this stackoverflow post for the info: https://stackoverflow.com/a/28370156/522859

DbSet does not contain a definition for ‘FromSQL’ and no extension method ‘FromSql’ accepting an argument of type ‘DbSet‘ could be found.

Hi everyone,

I ran into the following error while attempting to use a custom query with EntityFramework:

DbSet does not contain a definition for ‘FromSQL’ and no extension method ‘FromSql’ accepting an argument of type ‘DbSet‘ could be found.

This one’s pretty straight forward:

// Install the following package via nuget
Install-package Microsoft.EntityFrameworkCore.Relational

//Add the following namespace to your file
using Microsoft.EntityFrameworkCore;

Hopefully that’ll solve it for you, but if not there’s a lot a more information in these posts:
https://stackoverflow.com/a/38919326/522859
https://github.com/npgsql/Npgsql.EntityFrameworkCore.PostgreSQL/issues/146

Include UserId in Login Response (Token) – Web API 2

Hi everyone,

A quick post on how to include the user’s id in your login response when using Web API 2.

The default response to the /Token request is as follows:

{
“access_token”: “xxxxxxxxxxxxx_xxxx”,
“token_type”: “bearer”,
“expires_in”: 1209599,
“userName”: “test@test.com”,
“.issued”: “Mon, 23 Apr 2018 06:08:03 GMT”,
“.expires”: “Mon, 07 May 2018 06:08:03 GMT”
}

Once the changes below have been made the response will include a userId field:

{
“access_token”: “xxxxxxxxxxxxx_xxxx”,
“token_type”: “bearer”,
“expires_in”: 1209599,
“userName”: “test@test.com”,
“.issued”: “Mon, 23 Apr 2018 06:08:03 GMT”,
“.expires”: “Mon, 07 May 2018 06:08:03 GMT”,
“userId”: “xxxxxxx”
}

There are three very small changes required in order to add this functionality.

First, add an additional argument to CreateProperties in ApplicationOAuthProvider.cs

public static AuthenticationProperties CreateProperties(string userName, string userId)
{
IDictionary data = new Dictionary
{
{ "userName", userName },
// Add
{ "userId", userId }
};
return new AuthenticationProperties(data);
}

Pass userId to CreateProperties in ApplicationOauthProvider.

// ApplicationOAuthProvider.cs > GrantResourceOwnerCredentials
ClaimsIdentity oAuthIdentity = await user.GenerateUserIdentityAsync(userManager, OAuthDefaults.AuthenticationType);
ClaimsIdentity cookiesIdentity = await user.GenerateUserIdentityAsync(userManager,
CookieAuthenticationDefaults.AuthenticationType);

// Add user id
AuthenticationProperties properties = CreateProperties(user.UserName, user.Id);
AuthenticationTicket ticket = new AuthenticationTicket(oAuthIdentity, properties);
context.Validated(ticket);

Pass userId to CreateProperties in AccountController.

// AccountController.cs > GetExternalLogin
if (hasRegistered)
{
Authentication.SignOut(DefaultAuthenticationTypes.ExternalCookie);

ClaimsIdentity oAuthIdentity = await user.GenerateUserIdentityAsync(UserManager, OAuthDefaults.AuthenticationType);
ClaimsIdentity cookieIdentity = await user.GenerateUserIdentityAsync(UserManager,
CookieAuthenticationDefaults.AuthenticationType);

// Add userid
AuthenticationProperties properties = ApplicationOAuthProvider.CreateProperties(user.UserName, user.Id);
Authentication.SignIn(properties, oAuthIdentity, cookieIdentity);

Unsupported_Grant_Type – MVC Web Api (error)

Hi everyone,

I ran into the following error while attempting to authenticate using .NET Web Api:

POST http://localhost:63720/Token HTTP/1.1
Host: localhost:63720
Content-Type: application/json
Content-Length: 0
HTTP/1.1 400 Bad Request
Content-Type: application/json;charset=UTF-8
Date: Mon, 16 Apr 2018 14:18:06 GMT
Content-Length: 34

{“error”:”unsupported_grant_type”}

This one was pretty straight forward. Ensure that have the correct content-type:

Content-Type: application/x-www-form-urlencoded

And finally, ensure that you provide a grant type in the request body:

grant_type=password&username=test_username&password=test_password

Thanks to the following stackoverflow post for the info: https://stackoverflow.com/a/29261024/522859

Exited with code 9009 – Visual Studio Build

Hey everyone,

I ran into the following error today while attempting to build a solution:

combiner exited with code 9009

It apparently means that a file couldn’t be found. The solution was to simply restart visual studio.

I’d been manually adding them to the directory and this is apparently a common cause. See the following Stackoverflow post for more info: https://stackoverflow.com/a/28198020/522859

Unable to Access RDS Database from Elastic Beanstalk Application

Hey everyone,

I ran into a bit of an issue today where I was unable to access my RDS SQL Express instance from my .NET Elastic Beanstalk instance. I was receiving the following error:

  1. The server was not found or was not accessible.

The solution turned out to be fairly simply thanks to this StackOverflow post: http://stackoverflow.com/a/33207022/522859

Get your server instance security group:
– Log into AWS
– Navigate to elastic beanstalk
– Open your application instance
– Open configuration
– Open instances
– Find “server” on the page and copy the value in the “EC2 security groups” field

Add your server instance security group to your rds rules:
– Navigate to the RDS Dashboard
– Open your RDS instance
– Click on view details (left hand side or top)
– Find Security and Network
– Click on the rds-launch-wizard under security groups
– Click on inbound rules (very bottom currently)
– Add a new inbound rule with the copied security group as the source

Unilateral receiver not allowed in chained payment is restricted – Adaptive Payment DotNet SDK

Hey everyone,

Just an error I ran into today while using the Adaptive Payments SDK for C#/.NET:

Unilateral receiver not allowed in chained payment is restricted

Thankfully this one is fairly simple – one of the receivers hasn’t confirmed their account.

http://stackoverflow.com/a/32816078/522859

Could not find part of the path ‘C:\x\lib’ – Adding new Web API Project

Hey everyone,

I ran into the following error when I tried to add a new Web API project in Visual Studio Express 2015 for Web:

Could not find part of the path ‘C:\x\lib’

The workaround for this was to temporarily unbind the project from TFS: File > Source Control > Advanced > Change Source Control > Click unbind on each of the projects

While not the same problem, this post helped me out: https://github.com/NuGet/Home/issues/1164