Visual Studio 2026 Insiders

Visual Studio 2026 Insiders

Visual Studio 2026 Insiders was released on September 9th.
As someone who uses Visual Studio 2022 extensively on a daily basis, the long-awaited new version has arrived.
You might be thinking, "What is Insiders?" In short, it seems to be a preview version.

I promptly installed it.

The screen immediately after startup looked like this (Figure 1).
It's almost identical to 2022. If anything, the design of the icon in the upper left corner has changed slightly, perhaps?

Figure 1. Visual Studio 2026

In Visual Studio 2022, I had set the color theme to "Use system settings," so let's match that.
It can be changed from Tools > Options > All Settings > Environment > Visual Experience ¹, but if you look closely, the appearance of the options screen has changed from before (Figure 2).
Perhaps this is what they call Fluent UI ², it has a modern design.

Figure 2. All Settings > Environment > Visual Experience

I successfully changed the color theme.

Let's take a quick look at the changes.

.NET 10 Support

Visual Studio 2026 supports .NET 10.
When creating a new console application, .NET 10.0 (Preview) is now displayed as a framework option.

Figure 3. New console application creation

.NET 10.0 includes C# 14, which is the latest version of C#.
Here, I will create an extension property for C# 14.

if ("".IsEmptyOrNull)
{
    Console.WriteLine("文字列は空または null です");
}

public static class StringExtensions
{
    extension(string source)
    {
        public bool IsEmptyOrNull => string.IsNullOrEmpty(source);
    }
}

The execution result was as expected (Figure 4).

Figure 4. Execution result

Code Editor

The number of characters and lines in the currently selected area are now displayed at the bottom of the editor.
Additionally, the file's encoding is now displayed (Figure 5). This is convenient as you can check the file's encoding at a glance. Clicking on the encoding display area also brings up a menu to switch encodings. The previous procedure of saving with a different encoding using "Save As" has been simplified.

Figure 5. Code Editor

Markdown Preview Mermaid Support

Mermaid rendering is now supported in Markdown preview (Figure 6). As opportunities to draw diagrams in documents using Mermaid are increasing, this can be seen as a natural evolution.

Figure 6. Markdown Preview

Method Return Value Display

The return value of the method executed immediately before is now displayed during debugging (Figure 7).

Figure 7. Method return value display

Not only for regular methods, but as shown in the figure, the value of extension properties is also displayed (you can also see that extension properties internally have a get_ prefix).
This is a welcome feature addition, as there was previously no easy way to check return values, for example, when they were not assigned to a variable.

Incidentally, if multiple methods are called on a single line as shown below, only the return value of the first method appears to be displayed (Figure 8). This is a bit disappointing, but I look forward to future improvements.

Figure 8.

Search within Text Visualizer

This is another modest yet highly capable feature addition. You can now search within the Text Visualizer (Figure 9). Previously, it required copying the text, pasting it into another editor, and then searching, but that step is no longer necessary.

Figure 9. Text Visualizer

Code Coverage

The code coverage feature, previously limited to Enterprise Edition, is now available in Community Edition (Figure 10).

Figure 10. Code Coverage

Introduction of the New Solution File (.slnx)

When creating a new project, solution files are now created in the .slnx format.
The .slnx format is a feature provided in preview since .NET SDK 9.0.200, which addresses issues with the traditional .sln format files. ³

Let's compare the solution files for a console application created with Visual Studio 2022 and one created with Visual Studio 2026.

Visual Studio 2022

Microsoft Visual Studio Solution File, Format Version 12.00
# Visual Studio Version 17
VisualStudioVersion = 17.14.36414.22 d17.14
MinimumVisualStudioVersion = 10.0.40219.1
Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "ConsoleApp1", "ConsoleApp1\ConsoleApp1.csproj", "{09E299FB-241A-4E6A-8FB3-7B3C3673E019}"
EndProject
Global
	GlobalSection(SolutionConfigurationPlatforms) = preSolution
		Debug|Any CPU = Debug|Any CPU
		Release|Any CPU = Release|Any CPU
	EndGlobalSection
	GlobalSection(ProjectConfigurationPlatforms) = postSolution
		{09E299FB-241A-4E6A-8FB3-7B3C3673E019}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
		{09E299FB-241A-4E6A-8FB3-7B3C3673E019}.Debug|Any CPU.Build.0 = Debug|Any CPU
		{09E299FB-241A-4E6A-8FB3-7B3C3673E019}.Release|Any CPU.ActiveCfg = Release|Any CPU
		{09E299FB-241A-4E6A-8FB3-7B3C3673E019}.Release|Any CPU.Build.0 = Release|Any CPU
	EndGlobalSection
	GlobalSection(SolutionProperties) = preSolution
		HideSolutionNode = FALSE
	EndGlobalSection
	GlobalSection(ExtensibilityGlobals) = postSolution
		SolutionGuid = {8DE17906-353E-4A90-B34A-C4752C111637}
	EndGlobalSection
EndGlobal

Visual Studio 2026

<Solution>
  <Project Path="ConsoleApp1/ConsoleApp1.csproj" />
</Solution>

The solution file, which used to be a mysterious proprietary format, has been changed to a simple XML format.

GitHub Copilot Integration

A major topic for Visual Studio 2026 is the integration with AI assistance features (GitHub Copilot). ⁴
GitHub Copilot could be used with previous versions of Visual Studio, but various new features have been added in 2026.

• Other LLMs besides OpenAI (ChatGPT) are available (Anthropic Claude, Google Gemini)
• Adaptive paste
• Addition of context menu for Copilot

Copilot operates integrated with the code editor.
Below are the steps taken when asking Copilot about a compilation error and applying Copilot's suggested fix (Figures 11 to 16).

Figure 11. Copilot context menu

Figure 12. Asking Copilot integrated into the editor

Figure 13. Copilot's answer

Figure 14. Copilot's suggested fix

Figure 15. Selecting "Apply" for Copilot's suggested fix

Figure 16. Confirming the fix with the Tab key

You can also have Copilot write comments by right-clicking > Copilot Actions > Generate Comments (Figure 17).

Figure 17. Comments suggested by Copilot

Summary

Visual Studio 2026 (Insiders ≈ preview version), the first new version in about four years, addresses the recent trend of effective AI utilization while also bringing practical updates to existing features, showing a steady evolution. Since my Korochin Site project has migrated to .NET 10, I will continue to use the Insiders version.

I'm looking forward to the official release.

References

Visual Studio Insiders リリース ノート | Microsoft Learn