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Develop API WebApp

The objective is to create an API WebApp for handling color objects.

Scaffold the basic solution​

Lets use GitHub Copilot Chat to help scaffold a basic API WebApp. The better the prompt, the better suggestion returned by GitHub Copilot.

  • From the previous section, we have already started VSCode and opened an empty folder.

  • Ask Copilot Chat the following.

I want to create dotnet 8.0 project usinng webapi template  - also need a MSTest unit Test project.
I need a project reference from Test project to API project.
The files should be called "Colors".  
List together the dotnet commands to scaffold a solution.

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Response will be something like this :

# Create a new solution
dotnet new sln -n Colors

# Create a new Web API project
dotnet new webapi -n Colors.API

# Create a new MSTest project
dotnet new mstest -n Colors.Tests

# Add the projects to the solution
dotnet sln Colors.sln add Colors.API/Colors.API.csproj
dotnet sln Colors.sln add Colors.Tests/Colors.Tests.csproj

# Add a project reference from the test project to the API project
cd Colors.Tests
dotnet add reference ../Colors.API/Colors.API.csproj

  • Within VSCode open up terminal. Use the commands suggested by Copilot Chat.
    • Notice the files created. Two projects (API and Test).

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  • Open Solution file - use F1 .NET Open Solution.

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  • Open Program.cs - remove existing Routes & Model (things to do with weather).

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We now have our basic API skeleton code - we shall now add the logic for our Colors API.

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Add Data model​

We first define the schema for our ColorsItem object:

  • Create ColorsItem.cs

  • Ask Copilot Chat the following

Create colors model called ColorsItem to include a name and hexcode.
  • Insert code into ColorsItem.cs

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  • Switch back to Program.cs

  • Ask Copilot Chat the following:

Intialize a list of ColorsItem with  "red", "yellow", "black"
  • Insert code into Program.cs

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Add API routes​

  • Ask Copilot Chat the following:
using ColorsItem - create two API routes.
First - an API to return all colors.   
Second - an API to insert a new color.
im using .NET 8 minimal APIs

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You can also prompt using an inline comment

//add a route to return a random color

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  • Hit Tab to accept the suggestion. Or use Alt [ and Alt ] to view alternatives.

Add Utility function​

Wwe shall now add some logic to validate the hexcode passed in the API call to add a new color.

  • Create file ColorUtilities.cs and add code .

  • Ask Copilot Chat the following.

I want a new static class called ColorUtilities.
I want a ValidateHexCode function using Regex - add to static class  ColorUtilities.
  • Insert code into ColorUtilities.cs.

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  • Irrespective of the code suggested, for lab purposes only check for 6 character hexcodes - we will fix this later.
  string pattern = @"^#([A-Fa-f0-9]{6})$";   // 6 character 
  string pattern = @"^#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})$";   // 3 or 6 character
  • Try this inline comment:
// function to test for shade of red

  • Switch back to Program.cs.

  • Add Hexcode validation to the Insert new Color route . Might need encouragement / prompting to use our validation utility function.

// hexcode validation

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Run the API WebApp​

Our API code is now complete

  • Use F5 to run the application.

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Use the Swagger UI to test the WebApi

  • Get all Colors.

  • Add a new color - use valid hexcode.

  • Add a new color - use invalid hexcode ... check for error status code.

  • Get a random color.

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