Category Archives: Web API

eShopOnContainers – No parameterless constructor defined for type dbcontext

Hi everyone,

Another eShopOnContainers post. Today I was setting up migrations and ran into the following error:

Found DbContext ‘CatalogContext’.
Microsoft.EntityFrameworkCore.Design.OperationException: Unable to create an object of type ‘CatalogContext’. For the different patterns supported at design time, see https://go.microsoft.com/fwlink/?linkid=851728
—> System.MissingMethodException: No parameterless constructor defined for type ‘Catalog.Api.Infrastructure.CatalogContext’.
at System.RuntimeType.CreateInstanceDefaultCtorSlow(Boolean publicOnly, Boolean wrapExceptions, Boolean fillCache)

This turned out to be because I was missing the following from my CatalogContext:

public class CatalogContextDesignFactory : IDesignTimeDbContextFactory
{
public CatalogContext CreateDbContext(string[] args)
{
var optionsBuilder = new DbContextOptionsBuilder()
.UseSqlServer(“Server=.;Initial Catalog=Microsoft.eShopOnContainers.Services.CatalogDb;Integrated Security=true”);

return new CatalogContext(optionsBuilder.Options);
}
}

error : “Timestamp” is not defined. – .net core and gRPC

Hi everyone,

I’m currently testing out gRPC with .NET Core and hit the following error when attempting to add a timestamp field to my proto file:

error : “Timestamp” is not defined.

My proto file was as follows:

syntax = “proto3”;
import “google/protobuf/timestamp.proto”;

option csharp_namespace = “publisher_api”;

package Weather;

// The weather forecast service definition
service Weather {

// Gets weather forecast
rpc Forecast(WeatherForecastRequest) returns (WeatherForecastResponse);
}

// The request message
message WeatherForecastRequest {

}

// The response message
message WeatherForecastResponse {
timestamp date = 1;
int32 temperatureC = 2;
int32 temperatureF = 3;
string summary = 4;
}

The solution was to fully qualify the timestamp namespace:


message WeatherForecastResponse {
google.protobuf.Timestamp date = 1;
int32 temperatureC = 2;
int32 temperatureF = 3;
string summary = 4;
}

Also ensure that you’ve added the protobuff package:

dotnet add package Google.Protobuf

See the following repo for a full example: https://github.com/Buzzology/microservicesDockerRabbitMQ

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:


    
    
        
        
        
    
    

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

Error Number:8152,State:10,Class:16 String or binary data would be truncated. The statement has been terminated. – Entity Framework

Hi everyone,

I ran into the following error after adding model validation attributes to a database with existing values:

Error Number:8152,State:10,Class:16
String or binary data would be truncated.
The statement has been terminated.

The solution is pretty straightforward if you’re happy to truncate the values. Simply run the query below, swapping Title for your column name, Products for your table name and 25 for your new column length:

UPDATE Products
SET Title = LEFT(Title, 25)
WHERE LEN(Title) > 25

You should then be able to run update-database without any issues:

PM> update-database
Specify the ‘-Verbose’ flag to view the SQL statements being applied to the target database.
Applying explicit migrations: [201806240741543_product_validation].
Applying explicit migration: 201806240741543_product_validation.
Running Seed method.
PM>

Thanks to David in for his answer on Stackoverflow: https://stackoverflow.com/a/24931522/522859

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

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);