source: README.md

# PostgreSQL ASP.NET 7

Convert an ASP.NET Core Web Application project to use PostgreSQL with Entity Framework.

This enables development of ASP.NET Core projects using [VS Code](https://code.visualstudio.com/) on macOS or linux targets.

This project uses [.NET 7.0](https://dotnet.microsoft.com/en-us/download/dotnet/7.0) target framework, ASP.NET Core Web Application MVC project scaffold from Visual Studio 2022 (version 17.4).

![vscode](https://user-images.githubusercontent.com/1213591/210010019-e4b11daf-03df-41b6-b44c-368f0cd3cfde.png)

Project setup has already been completed in this repository - assure [environment setup](#environment-setup); then, jump to [running the solution](#running-the-solution).


## Environment Setup

This project requires PostgreSQL - installation instructions are provided below.

If using Visual Studio Code, you will need to generate ASP.NET Core developer certificates by issuing the following commands from a terminal:

    dotnet dev-certs https --clean
    dotnet dev-certs https

For command line `database ef` commands, you will need to install Entity Framework Core tools .NET CLI:

    dotnet tool install --global dotnet-ef


## Project Setup


Below, instructions are referenced to use PostgreSQL in a ASP.NET Core project.


### Install NuGet packages

Install the `Npgsql.EntityFrameworkCore.PostgreSQL` NuGet package in the ASP.NET web application.

To do this, you can use the `dotnet` command line by executing:

    $ dotnet add package Npgsql.EntityFrameworkCore.PostgreSQL --version 3.1.2

Or, edit the project's .csproj file and add the following line in the `PackageReference` item group:

```xml
<PackageReference Include="Npgsql.EntityFrameworkCore.PostgreSQL" Version="3.1.2" />
```


### Update appsettings.json

Configure connection string in project's appsettings.json, replacing the `username`, `password`, and `dbname` appropriately:

```json
"ConnectionStrings": {
    "DefaultConnection": "User ID=username;Password=password;Server=localhost;Port=5432;Database=dbname;Integrated Security=true;Pooling=true;"
},
```


### Modify Program.cs

Inside Program.cs replace the `UseSqlServer` options with `UseNpgsql`:

```cs
builder.Services.AddDbContext<ApplicationDbContext>(options =>
    options.UseNpgsql(connectionString));
```
    

## Running the solution

Before the solution can be executed, be sure to run entity framework migrations.


### Migration Issues with DbContext

Initial migrations may fail, due to ASP.NET Core template come with a pre-generation migration for SQL Server.

When trying to run the migration, you might see errors such as:
> Npgsql.PostgresException (0x80004005): 42704: type "nvarchar" does not exist
>
> System.NullReferenceException: Object reference not set to an instance of an object.
>
> System.InvalidOperationException: No mapping to a relational type can be found for property 'Microsoft.AspNetCore.Identity.IdentityUser.TwoFactorEnabled' with the CLR type 'bool'.

Delete the entire Migrations folder, and regenerate new inital migrations.

Generate a new migration using Visual Studio Package Manager Console (from menu: Tools -> NuGet Package Manager -> Package Manager Console):

    PM> Add-Migration

Or, from the command line via DotNet CLI:

    $ dotnet ef migrations add Initial

If dotnet migration tools don't exist, remember to install the tools using the instruction above in the [environment setup](#environment-setup).


### Run Entity Framework Migrations

Execute the migration using either Visual Studio Package Manager Console (from menu: Tools -> NuGet Package Manager -> Package Manager Console):

    PM> Update-Database

Or, from the command line via DotNet CLI, execute the following command inside the project directory, **where the .csproj file is located**:

    $ dotnet ef database update

After running the migration, the database is created and web application is ready to be run.


## Setting up a PostgresSQL server on Mac

Here are instructions to setup a PostgreSQL server on Mac using Homebrew.


### Installing PostgreSQL on Mac

Use [brew](https://brew.sh/) to install PostgreSQL, then launch the service:

    $ brew install postgresql
    $ brew services start postgresql


### Create a user

Create a user using the `createuser` command from a terminal, where `username` is your desired new user name.  Using the `-P` argument, you will be prompted to setup a password.

    $ createuser username -P


### Create a database

Create your database using the `createdb` command from a terminal, where `dbname` is your desired new database name.

    $ createdb dbname
    
At this time, run the solution's Entity Framework migrations (see above for instructions).


### Verifying database

Launch PostgreSQL interactive terminal and connect to the database.

    $ psql dbname


From the PostgreSQL interface terminal, List tables using the `\dt` command:

    dbname=# \dt
                       List of relations
     Schema |         Name          | Type  |    Owner     
    --------+-----------------------+-------+--------------
     public | AspNetRoleClaims      | table | username
     public | AspNetRoles           | table | username
     public | AspNetUserClaims      | table | username
     public | AspNetUserLogins      | table | username
     public | AspNetUserRoles       | table | username
     public | AspNetUserTokens      | table | username
     public | AspNetUsers           | table | username
     public | __EFMigrationsHistory | table | username
    (8 rows)


### Database permissions issues

If permissions were not setup properly during the creation of the database, retroactively fix by granting privileges where `dbname` is your database name and `username` is the user you created:

    $ psql dbname
    dbname=# GRANT ALL PRIVILEGES ON ALL TABLES IN SCHEMA public TO username;