C# on Junian Dev

Blazor Apps by Junian.dev

author@junian.dev (Junian Triajianto) — Wed, 28 Jan 2026 06:00:00 +0700

Run a .NET App from a Single C# File

author@junian.dev (Junian Triajianto) — Sat, 27 Sep 2025 05:44:27 +0700

With .NET 10, you can run a C# file directly, no project or solution file required!

This is especially useful for automation scripts, DevOps tasks, or quick experimentation.

In this tutorial, I’ll show you how it works on macOS (or any supported Unix-based system).

Getting Started with dotnet app run.cs

First, install the .NET 10 SDK.

On macOS, you can use Homebrew:

brew install junian/dotnet/dotnet-sdk@10.0

Create a new file and make it executable:

WinForms 32-bit 'Designer Could Not Be Shown' Issue

author@junian.dev (Junian Triajianto) — Sun, 09 Mar 2025 10:30:40 +0700

When I was working on a company WinForms project in Visual Studio, I encountered the following error:

The designer could not be shown for this file because none of the classes within it can be designed. The designer inspected the following classes in the file: frmDataEditor — The base class ‘Client.Forms’ could not be loaded. Ensure the assembly has been referenced and that all projects have been built.

Here’s the complete Stack Trace:

Fizz Buzz - LeetCode in C#

author@junian.dev (Junian Triajianto) — Thu, 14 Nov 2024 12:01:57 +0700

The Fizz Buzz problem is a classic exercise that is often used to teach basic programming concepts such as loops and conditionals.

In this article, I’ll show you my attempt to solve this problem.

Problem Description

Given an integer n, return a string array answer (1-indexed) where:

answer[i] == "FizzBuzz" if i is divisible by 3 and 5.
answer[i] == "Fizz" if i is divisible by 3.
answer[i] == "Buzz" if i is divisible by 5.
answer[i] == i (as a string) if none of the above conditions are true.

Example 1:

Input: n = 3
Output: ["1","2","Fizz"]

Example 2:

Input: n = 5
Output: ["1","2","Fizz","4","Buzz"]

Example 3:

Input: n = 15
Output: ["1","2","Fizz","4","Buzz","Fizz","7","8","Fizz","Buzz","11","Fizz","13","14","FizzBuzz"]

Constraints:

1 <= n <= 10⁴

Intuition

When breaking down the problem, the task is to iterate through a sequence of numbers while applying simple divisibility rules to determine the correct output for each number.

Palindrome Number - LeetCode in C#

author@junian.dev (Junian Triajianto) — Sun, 10 Nov 2024 17:03:55 +0700

Problem

Given an integer x, return true if x is a palindrome , and false otherwise.

Example 1:

Input: x = 121
Output: true
Explanation: 121 reads as 121 from left to right and from right to left.

Example 2:

Input: x = -121
Output: false
Explanation: From left to right, it reads -121. From right to left, it becomes 121-. Therefore it is not a palindrome.

Example 3:

Input: x = 10
Output: false
Explanation: Reads 01 from right to left. Therefore it is not a palindrome.

Constraints:

Remove Duplicates From Sorted Array - LeetCode in C#

author@junian.dev (Junian Triajianto) — Sat, 09 Nov 2024 14:46:13 +0700

Problem Description

Given an integer array nums sorted in non-decreasing order, remove the duplicates in-place such that each unique element appears only once. The relative order of the elements should be kept the same. Then return the number of unique elements in nums.

Consider the number of unique elements of nums to be k, to get accepted, you need to do the following things:

Change the array nums such that the first k elements of nums contain the unique elements in the order they were present in nums initially. The remaining elements of nums are not important as well as the size of nums.
Return k.

Custom Judge:

Two Sum - LeetCode in C# - Hash Table Solution

author@junian.dev (Junian Triajianto) — Fri, 08 Nov 2024 18:51:32 +0700

Problem

Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target.

You may assume that each input would have exactly one solution, and you may not use the same element twice.

You can return the answer in any order.

Example 1:

Input: nums = [2,7,11,15], target = 9
Output: [0,1]
Explanation: Because nums[0] + nums[1] == 9, we return [0, 1].

Example 2:

Two Sum - LeetCode in C# - Brute force approach

author@junian.dev (Junian Triajianto) — Fri, 08 Nov 2024 13:39:47 +0700

You might want to read the Hash Table solution. It’s better.

Intuition

When I first encountered the Two Sum problem, my initial thought was to check each possible pair of numbers in the array. If a pair sums to the target value, then that would be our solution.

This brute force method should work, but intuitively, I thought there might be more efficient ways.

However, starting with the simplest idea often helps to understand the problem better and refine the approach.

Folder Browser Dialog on Windows with C#

author@junian.dev (Junian Triajianto) — Sun, 05 May 2024 13:42:11 +0700

In this guide, I’ll walk you through the process of implementing a folder selection UI using C#.

In many applications, users need to specify a folder where certain files will be saved or retrieved. Providing a user-friendly way to select folders enhances the overall usability of your application.

To implement a folder selection dialog in C#, we’ll use the FolderBrowserDialog class provided by the .NET framework. This class allows users to browse and select folders from their file system with ease.

Can't Open Form [Design] View in WinForms Project

author@junian.dev (Junian Triajianto) — Sun, 05 May 2024 09:48:56 +0700

Have you ever been developing a WinForms project and encountered a situation where you couldn’t use the View Designer?

This problem can occur when you’re using the latest SDK-style project but are still targeting an older version of .NET, such as 4.8 or below.

Rest assured, you’re not alone. The solution is rather straightforward.

In Visual Studio, simply right-click on your project file and select Edit Project File.

Now, you just need to include a new ItemGroup for your Form files.

VSCode Avalonia Extension Download .NET Runtime Issue

author@junian.dev (Junian Triajianto) — Wed, 17 Apr 2024 16:08:38 +0700

So I want to start using AvaloniaUI on macOS, but suddenly it always happens.

AvaloniaTeam.vscode-avalonia requested to download the .NET Runtime. Downloading .NET version(s) 8.0.4~arm64 ….Error Failed to download .NET 8.0: Web Request to https://dot.net/v1/dotnet-install.sh Failed: n[r].split is not a function. Aborting. Please ensure that you are online.

To solve that, just open the VSCode settings.json and configure it with the following settings.

"dotnetAcquisitionExtension.existingDotnetPath": [
    {
        "extensionId": "ms-dotnettools.csharp",
        "path": "/usr/local/share/dotnet/dotnet"
    },
    {
        "extensionId": "ms-dotnettools.csdevkit", 
        "path": "/usr/local/share/dotnet/dotnet"
    },
    {
        "extensionId": "visualstudiotoolsforunity.vstuc", 
        "path": "/usr/local/share/dotnet/dotnet"
    },
    {
        "extensionId": "AvaloniaTeam.vscode-avalonia", 
        "path": "/usr/local/share/dotnet/dotnet"
    },
]

That’s it, now you can use AvaloniaUI on VSCode with auto-complete and everything.

String Comparison by Ignoring Case in C#

author@junian.dev (Junian Triajianto) — Thu, 02 Apr 2020 10:19:09 +0700

String value in C# is case-sensitive. That means lower case and upper case texts are considered different when you compare them.

But, there are some cases when you need to compare two strings and ignore their case. For example when you’re building a search engine.

To compare two strings by ignoring their case, you can just put an additional parameter when you’re using string.Equals() method.

Take a look the following snippet as an example.

Base64 String Encoding and Decoding in C#

author@junian.dev (Junian Triajianto) — Tue, 31 Mar 2020 20:28:58 +0700

Base64 is a radix-64 ASCII string format that represents binary data. Each digit of base64 encoded string represents exactly 6 bits of data.

It is designed to carry binary data across platforms that only support text content.

The usage is mostly popular in Web platform. For example it’s being used to embed image files inside HTML or embed font file inside CSS.

Even though the main purpose is to store binary data into a text content, base64 sometimes is being used to hide a text. For example to prevent the content of your website scraped by robot.

'Hello, World!' Program in C#

author@junian.dev (Junian Triajianto) — Tue, 31 Mar 2020 19:25:12 +0700

Hi, welcome to C# FAQs. I create this section to collect and write frequently used C# methods. I will also write the description, or the step by step tutorial with simple english so you can understand it easily.

For the first post, I’ll show you how to write a C# program that prints “Hello, World!” on your screen. This is the simplest program in any programming language. It’s a good first step for anyone learning to code. After you finish this, you’ll understand the basic syntax in C#.

Save C# Image Object into Oracle BLOB

author@junian.dev (Junian Triajianto) — Wed, 13 Nov 2019 06:00:13 +0700

Some of my friends requested me to make a tutorial about the Oracle database and C#. This time, I’d like to share about how to Save Image or Picture from C# Object into Oracle BLOB Type. It’s very easy if you know the trick.

To make the tutorial simple, let’s assume a table with 1 field. It’ll be used to store a collection of photos.

CREATE TABLE PHOTO 
(
  PHOTO_BIN BLOB 
);

Next, open or create a new C# project. Add Oracle.ManagedDataAccess NuGet package to your project.

Complete C# String Hash Functions

author@junian.dev (Junian Triajianto) — Fri, 14 Sep 2018 06:34:40 +0700

For a while I’ve been seeing my blog traffic and surprisingly there are some of you are landed here by searching about MD5 string hash in C#, specifically used for storing password. I wrote the first draft of that tutorial when I was still in college while learning C# as a student, so it’s really old tutorial.

As we know, MD5 isn’t recommended anymore because it is designed to be very fast and efficient. By using modern computers and techniques, it is possible to “brute force” the hash output, in order to retrieve the original input. Because of this, many security experts suggest not to use it for password hashing.

Solving Sharepoint ClientContext Socket Exception in C#

author@junian.dev (Junian Triajianto) — Fri, 07 Sep 2018 06:39:53 +0700

So, you’ve been writing a Sharepoint client application and it’s running just fine. After several weeks or months, you noticed some errors were showing up. If you see a lot of SocketException error messages like following snippet, then this article is for you.

System.Net.WebException: Unable to connect to the remote server ---> System.Net.Sockets.SocketException: Only one usage of each socket address (protocol/network address/port) is normally permitted 127.0.0.1:443
     at System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress)
     at System.Net.ServicePoint.ConnectSocketInternal(Boolean connectFailure, Socket s4, Socket s6, Socket& socket, IPAddress& address, ConnectSocketState state, IAsyncResult asyncResult, Exception& exception)

In my previous article about Sharepoint CSOM Socket Exception, I wrote about on how to solve this issue by editing some registry values. I did it and worked beautifully, but only for several days.

Running Your First ASP.NET Core Web App with MySQL on Ubuntu 16.04

author@junian.dev (Junian Triajianto) — Tue, 24 Jan 2017 09:15:00 +0000

Since Microsoft open sourcing their .NET Platform, which is called .NET Core, they stole my attention again. I always love using .NET Framework. I develop desktop apps using it. I develop mobile apps using Xamarin. But I rarely use its web platform for one simple reason, it requires Windows-based Server to run.

Now that Microsoft and community actively develop its framework for cross-platform environment, I stumble upon and see the latest stable build which is version 1.1. I read their blog and found out about news that ASP.NET Core 1.1 with Kestrel was ranked as the fastest mainstream fullstack web framework in the TechEmpower plaintext benchmark. That’s such a nice claim and gave me attention to try their product.

Camera Face Detection in C# using Emgu CV and WPF

author@junian.dev (Junian Triajianto) — Thu, 29 Dec 2016 09:49:00 +0000

Hi there, this is a new tutorial category in my blog. It’s Computer Vision. In this blog, I’d like to show you something cool. It’s how to perform Face Detection using your camera or Webcam. You’ll see how your application can detect faces from a captured image. Curious about it? Let’s take a look how to do that.

This what you need to follow this tutorial:

Microsoft Visual Studio 2010. Or if you don’t have one, you can use 2008 version.
Emgu CV (OpenCV in .NET). You can download the latest version in this link: www.emgu.com/wiki/index.php/Main_Page and follow the installation instruction.
Basic Knowledge of C# Programming.
Familiar in WPF Development.

After you’ve got what you need, it’s time to rock!

Load External Image into WPF using OpenFileDialog

author@junian.dev (Junian Triajianto) — Tue, 13 Dec 2016 13:31:00 +0000

This is my first time I made a tutorial about WPF. I don’t think it’s a new technique, but I just want to share what I learned at home. I assume that you understand WPF a little bit. In this tutorial I’d like to show you how to load external image into WPF using OpenFileDialog.

Step 1

Create a new WPF Project, File → New → Project… and chose WPF Application (by the way, I’m using Visual Studio 2008 in this tutorial). You’ll see an empty window called Window1.xaml.

Password Encryption using MD5 Hash Algorithm in C#

author@junian.dev (Junian Triajianto) — Thu, 08 Dec 2016 09:57:00 +0000

Update (Sep 14, 2018): The new complete string hash algorithms in C# tutorial is available. I would suggest not to use MD5 anymore, because it’s not safe and easily collide. But I’ll leave the original tutorial here for educational purpose.

It’s really bad if someone knew your password. As a software developer, we have an ethic that we also don’t want to see other’s password. Which mean, storing password in a plain text is a nope.