Windows Core IoT – ASP DotNet Core Razor Pages & SQLite & Web Service on a Raspberry PI3

May 28, 2018

Building a Web Server App using ASP .Net Core using a SQLite Database and a Web Service starts here using this example.

https://docs.microsoft.com/en-us/aspnet/core/data/ef-rp/intro?view=aspnetcore-2.1

I gave it a little twist in order to get it to use an SQLite Database and add a Web Service to it.

This means you need to follow page 1 of 8 from this Tutorial to get the full deal. I only did page 1 & 2.

But make the necessary change mentioned below.

Keep in mind that the we will only use the command line options, and no bulk load of software needed to install Smile

Requirements are that you have Dotnet Core installed.

And have the DB using EF Tools installed from NuGet

Creating the  .Net Razor App

1. Create a new blank RAZOR project

Create a new folder in your PC and run the command to create a new RAZOR project

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Command : dotnet New Razor

This will create a new blank Razor project

2. Install the DB using EF Tools

Go to Nuget and look for this package

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I used the version 2.1.0-rc1-final

Run this command :

dotnet add package Microsoft.EntityFrameworkCore.Tools –version 2.1.0-rc1-final

After installation you can test is using this command :

dotnet ef

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3. Add more packages needed

dotnet add package Microsoft.EntityFrameworkCore.Tools.DotNet –version 2.1.0-preview1-final

dotnet add package Microsoft.VisualStudio.Web.CodeGeneration.Design –Version 2.0.0

dotnet add package Microsoft.VisualStudio.Web.CodeGeneration.Utils –Version 2.0.0

4. Add missing other packages

Correct the project .Json package references, by adding the missing packages from the Nuget Site :

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<Project Sdk="Microsoft.NET.Sdk.Web">
  <PropertyGroup>
    <TargetFramework>netcoreapp2.0</TargetFramework>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.AspNetCore.All" Version="2.0.6" />
    <PackageReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Design" Version="2.0.2" />
    <PackageReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Utils" Version="2.1.0-preview2-final" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Tools.DotNet" Version="2.1.0-preview1-final" />
    <DotNetCliToolReference Include="Microsoft.EntityFrameworkCore.Tools.DotNet" Version="2.0.0" />
    <PackageReference Include="Microsoft.CodeAnalysis.CSharp.Workspaces" Version="2.8.0" />
    <PackageReference Include="SQLitePCLRaw.bundle_green" Version="1.1.10" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Sqlite" Version="2.0.2" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Sqlite.Core" Version="2.0.2" />
  </ItemGroup>
  <ItemGroup>
    <DotNetCliToolReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Tools" Version="2.0.4" />
    <DotNetCliToolReference Include="Microsoft.EntityFrameworkCore.Tools.DotNet" Version="2.0.0" />
  </ItemGroup>
</Project>

Next run this command :

dotnet add xxxxx form the .NET CLI command.

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It downloads and installed the package selected on the NuGet site

Check you .Json Project file again afterward and continue with the rest of the missing packages

When finished run command :

dotnet Restore

5. Add the missing code to generate the DB

(Or generate the code based on an existing DB using Scaffolding)

Example : Create a Models folder. In the Models folder, create a class file named Student.cs

Content see example Microsoft site :

https://docs.microsoft.com/en-us/aspnet/core/data/ef-rp/intro?view=aspnetcore-2.1

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6. Create the xxxxContext DB context

xxx = School in my case


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In the Data folder create SchoolContext.cs

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This is where I modified the code to use SQLite instead of a Local DB

optionsBuilder.UseSqlite(@"Datasource=C:\CoreIoT\ASPnetRazorSQLiteWsAPI\Data\School.db");

In Startup.cs add the missing references (Using xxx) add the DB Context reference :

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Add the DB Context reference :

services.AddEntityFrameworkSqlite().AddDbContext<SchoolContext>(); // Added

In the Data folder, create a new class file named DbInitializer.cs see MS Example Site

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Which gets called by program.cs

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This will create the Database Tables, Fields and Records using the Entity Framework Tools.

Opposite, you can create View Pages from an existing Database using Scaffolding with the Entity Framework Tools too… Winking smile

Use a command like this to generate an EF Model from and existing Database

dotnet ef dbcontext scaffold “Datasource=C:\CoreIoT\ASPSQLite\Nwind.db” Microsoft.EntityFrameworkCore.Sqlite -o Models -c “DatabaseContext” –f

7. Generate the View pages based on the model you created before :

Courses : dotnet aspnet-codegenerator razorpage -m Course -dc SchoolContext -udl -outDir Pages\Courses –referenceScriptLibraries

Instructor : dotnet aspnet-codegenerator razorpage -m Instructor -dc SchoolContext -udl -outDir Pages\Instructors –referenceScriptLibraries

8. Correct the ERRORS, if needed…

When running the command in step 6 you can get ERRORS.

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Globally change _context.Student to _context.Students (add an “s” to Student)

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Quote from MS Site :

There are 7 occurrences found and updated. This is a bug and the hope to fix this bug in the next release.


=> TEST THE APP to see all errors are gone :

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cd to your project folder, next use this command :

Dotnet Run

9. BEFORE publishing add the following string in the program.cs and republish again.

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UseURLs(“http://*:5000)

10. Publish for RPI3 – ARM

Run this command : dotnet publish -r win8-arm

11. Copy from Publish to your RPI3

Copy the Files from the PUBLISH folder to your RPI3.

ASPRazor -> C:\CoreIoT\ASPnetRazorSQLiteWsAPI\bin\Debug\netcoreapp2.0\win8-arm\publish\

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Next MAKE SURE your FOLDER STRUCTURE on the RPI3, is exactly the same as it was on your PC before Publishing.

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Or you run into this error : ‘Unable to open database file’

Next COPY the SQLite Database to your RPI3. Because this is NOT included when publishing using DotNet Core to win8Arm

12. Test the .Net Razor App on your RPI3

Login using PowerShell WSMAN to your RPI and start the app.

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Go to the URL (it can take a while before all is loaded ….)

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Let access the database ?

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Let’s add some data ?

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Haleluja, this is fully functional and cross platform !!

Adding a Web Service to the .Net Razor App

Next I will add it to the site to see we can access the data using a Web Service API.

Again instead of using the full blown Visual Studio we will only use the command line options.

Because we don’t want to install an elephant weight of software !

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Actually Visual Studio uses all these commands in the background too … Winking smile

Run this command :

dotnet aspnet-codegenerator controller -api -name StudentAPIController -m Student -dc SchoolContext -udl -outDir Models\API –referenceScriptLibraries -f

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see the result

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You also have the option to generate XML instead of JSON

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Check the result !!

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This is how you you select ID 5

ID = 5

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It contains GET / POST / PUT / DELETE methods !

Accessing the Web Service using PowerShell

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CLS

$URL = "http://localhost:5000/api/StudentAPI"

$APIService = Invoke-RestMethod -Uri $URL

$APIService | select ID, lastName, firstMidName 

After copying to your RPI3 you can change the URL to http://rpi3:5000/api/StudentAPI

And test it …

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As you can see all runs fine, no Visual Studio needed …. Smile

So now you have a Web Service running on your RPI3, who could have imagined this … ?

Use Case :

Since you now have an SQLite DB running your can feed it with your RPI3 SENSOR data and read it out using the Web Smile

or even as a Web Service as demonstrated above …

Enjoy !

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Windows – Taskkill Error Access denied

May 17, 2018

Just a tip, sometimes when you run taskkill to kill a process you get the “access denied” Error.

Even if you run it with Admin privileges Sad smile

Example :

Taskkill /IM notepad.exe /T /F

SOLUTION :

Just use the WMIC cmdline tool instead Smile

wmic process where name=’notepad.exe’ delete

Enjoy !


MS SQL – Install only SSMS to do an Azure Backup

May 9, 2018

If you need to install only the SQL Management Studio these days, you will need to go to maximum SQL 2014 !

In the later versions this is not possible anymore to separately selecting the SSMS

Solution :

Download the version INCLUDING the ADVANCED TOOLS

https://www.microsoft.com/en-us/download/details.aspx?id=42299

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Use this option

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Choose only “Management Tools – Basic and Management Tools – Complete” as shown below:

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And you are ready to rock and roll … Smile

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Tip : When you need to do an SQL Azure Backup to an onside server YOU NEED SSMS a the tool to do so !

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It will save your SQL Backup as *.bacpac file

See here for more info :

https://mikhail.io/2016/10/azure-sql-databases-backups-disaster-recovery-import-export/

Export can also be triggered from Azure Portal and PowerShell scripts or using Command Line Tools :

Data-Tier Application Framework : https://www.microsoft.com/en-us/download/details.aspx?id=46898

SqlPackage.exe is part of the SSDT : https://docs.microsoft.com/en-us/sql/ssdt/download-sql-server-data-tools-ssdt?view=sql-server-2017

More info : https://msdn.microsoft.com/en-us/library/hh531248(v=vs.103).aspx

Enjoy !