Category Archives: Guides

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:

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”: “”,
“.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”: “”,
“.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,

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

Pass userId to CreateProperties in AccountController.

// AccountController.cs > GetExternalLogin
if (hasRegistered)

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

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

Cannot attach the file ‘C:\…database.mdf’ as database x – Entity Framework

Hi everyone,

I ran into the following error when attempting to run ‘update-database’ on an initial migration:

Cannot attach the file ‘C:\Users\…\App_Data\aspnet-…115933.mdf’ as database ‘aspnet-…15933’

The solution to this one is pretty easy, remove the initial catalog property from your connection string.

…33.mdf;Initial Catalog=aspnet…

This is apparently caused by issues with EntityFramework and multiple projects in the same database. See the following stackoverflow answer for more info:

Retrieving User Id in Web API 2 Controller – .NET

Hi everyone,

Just a quick post on how to retrieve the current user’s id in a Web API 2 controller:

var userId = RequestContext.Principal.Identity.GetUserId();

Note that you’ll need the following using statements:

using Microsoft.AspNet.Identity;
using System.Web.Http;

Thanks to the following stackoverflow post for the info:

Git Ignore Template for .NET

Hi everyone,

A sample .gitignore file for if you’re working with .net:


Also, if you happen to have added some files you didn’t mean to:

git rm –cached file_you_dont_want.pdb
git commit -m “Remove pdb file”

Thanks to these stackoverflow posts for the info:

Import an Existing Project to BitBucket

Hi everyone,

Today I needed to import an existing project to Bitbucket. The documentation is really good, but just in case you have trouble finding it:

  1. Navigate to the root directory of your project.
  2. Run the following commands in terminal/command prompt:
    git init
    git add –all
    git commit -m “Initial Commit”
  3. Login to Bitbucket and create repository.
  4. Locate the clone URL (left menu) e.g. https://email_address.bitbucket.domain:7999/project_name/repo.git
  5. Upload your files:
    git remote add origin https://email_address.bitbucket.domain:7999/project_name/repo.git
    git push -u origin master

    Check out the following link for more info:

Using INA219 (GY-219) with the Raspberry Pi

Hi everyone,

I’ve just setup an INA219B Voltage/Current sensor on my RaspberryPi. Just thought I’d link the tutorials and libraries I used – there’s a lot of really useful info out there.

Install the following library via git:
sudo pip3 install pi-ina219

Follow this tutorial:

Misc Notes

  • Common ground is required
  • Vin – and Vin+ are attached to +, neither goes to ground

Custom Sensor Address
na = INA219(SHUNT_OHMS, MAX_EXPECTED_AMPS, address=0x41)

Can be configured via the following:

Enable Low Power Between Reads
while True:
print "Voltage : %.3f V" % ina.voltage()

Mini-360 DC-DC Buck Converter – Incorrect Voltage 10v Instead of 5v

Hi everyone,

I’ve been playing around with a few DC-DC buck converters similar to these ones:

I had expected 5v output from my 12v supply but when I hooked it up to a multimeter I found I was getting just over 10v. This would fry pretty much everything in my circuit so I was pretty worried.

After a bit of research, I came across a thread on eevblog that mentioned a screw for adjustment. Looking closely you can see that there is a small screw on the side of the chip. Turning this quarter of a rotation anti-clockwise put mine at exactly 5.04 volts.

A few other small tips:

  • The thread seems to indicate that some models require a lot more turning (up to 30 seconds for one poster).
  • I had to push down fairly hard to get it to actually turn the part underneath instead of just the metal cover

Hopefully this helps someone else out!



Duinotech Hall Effect Sensor with RaspberryPi

Hi everyone,

This is just a quick post to cover how the Duinotech hall effect sensor module (XC-4434) can be hooked up to a RaspberryPi.

Sample Code

The code below will output a zero when the sensor is activated by a magnet, otherwise a zero.

import time
import datetime
import RPi.GPIO as GPIO

# Define constants

# Setup GPIO pins
GPIO.setup(BUCKET_HALL_EFFECT_SIG_PIN, GPIO.IN, pull_up_down=GPIO.PUD_UP) # Important

while True:



When near a magnetic field the light on the sensor will turn on. If you’re using the sample code above, a zero will be shown when close to a magnet, otherwise a 1.


Purchased from:

Spec Sheet: Z7275

Updating to Python 3.5.1 on RaspberryPi

Hi everyone,

Just a quick post on how to update to Python 3.5.1 the normal upgrade process isn’t working for you:

cd ~
tar -zxvf Python-3.5.1.tgz
cd Python-3.5.1
./configure && make && sudo make install

You may need to restart once this is complete. Run the following to confirm that the version is 3.5.1:

pi@raspberrypi:~ $ python3 --version
Python 3.5.1

Check out the following link for more info: