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The Easiest Way to Learn Design Patterns in C#

Builder: Implementation and Example

Explore how to implement the Builder design pattern by creating a cross-platform audio player in C#. Understand how to build OS-specific player components step-by-step, utilizing abstractions and concrete classes to assemble the final product. This lesson helps you apply Builder pattern concepts to real-world scenarios for flexible software design.

We'll cover the following...

In our example, we’ll once again build an audio player that can play audio on both Linux and Windows operating systems, as we did for Factory Method and Abstract Factory. This time, we’ll do so by using the Builder design pattern.

Creating a console application

We’ll start by creating a .NET console application. We’ll first add some static utility classes that’ll provide audio playback functionality on both Windows and Linux.

Implementing the utility classes

For the Linux implementation, we’ll add the LinuxPlayerUtility.cs file with the following content:

C#
using System.Diagnostics;
namespace Builder_Demo;
internal static class LinuxPlayerUtility
{
    public static Process? PlaybackProcess { get; set; } 
    public static void StartBashProcess(string command)
    {
        var escapedArgs = command.Replace("\"", "\\\"");
        var process = new Process()
        {
            StartInfo = new ProcessStartInfo
            {
                FileName = "/bin/bash",
                Arguments = $"-c \"{escapedArgs}\"", 
                RedirectStandardOutput = true, 
                RedirectStandardInput = true, 
                UseShellExecute = false, 
                CreateNoWindow = true,
            }
        };
        process.Start();
    }
}

Windows implementation will be placed into the WindowsPlayerUtility.cs file, which will contain the following code:

C#
using System.Runtime.InteropServices;

using System.Text;



namespace Builder_Demo;



internal static class WindowsPlayerUtility

{

    [DllImport("winmm.dll")]

    private static extern int mciSendString(string command,StringBuilder stringReturn,int returnLength,IntPtr hwndCallback);

    public static void ExecuteMciCommand(string commandString)

    {

        var sb = new StringBuilder();

        var result = mciSendString(commandString, sb, 1024*1024,IntPtr.Zero); 

        Console.WriteLine(result);



    }

}

Implementing the “Play” button

We’ll then add the PlayButton.cs file, ...