Advanced C# Optimizer, FRX Image Viewer, and Accessibility Overhaul in VB Decompiler v26.1

We are pleased to announce the release of VB Decompiler version 26.1. This is a major feature update that delivers a deeply reworked C# code optimizer, a brand-new built-in plugin, full NVDA screen reader compatibility, and a wide range of stability and usability improvements.

Next-Generation C# Procedure Optimizer

The most significant technical achievement in version 26.1 is the all-new procedure analyzer and optimizer for C# code. It operates on decompiled output from any .NET language - C#, VB .NET, F#, and others. And transforms raw, compiler-generated IL patterns into clean, human-readable C# source.

Loop Reconstruction

Raw decompiled .NET code is full of goto statements and labels that represent structured loops in the original source. The optimizer now fully reconstructs these patterns:

• while loops - detected and reconstructed from goto/label patterns.
• do-while loops - correctly identified even when the condition variable is declared inside the loop body.
• foreach loops - rebuilt from the full GetEnumerator / MoveNext / Dispose scaffolding, including try/finally wrappers generated by the compiler.
• Nested loops - while-in-while, while-in-foreach, while-in-if combinations are all emitted correctly inline.
• Loop condition inlining - intermediate temporary variables assigned just before a loop test are folded directly into the while header, eliminating clutter.

If/Else Reconstruction

Conditional branches expressed as chains of goto instructions are now rebuilt into proper if/else structures:

• Standard if/else chains reconstructed from conditional goto patterns.
• Negated conditions normalized - operator method calls such as op_Equality and op_Inequality are replaced with their readable equivalents (==, !=).
• Filter goto chains - multiple chained if+goto sequences targeting the same label are preserved correctly when the resulting body would be empty, always maintaining semantic correctness over visual tidiness.

Expression Optimization

The optimizer now handles a wide range of expression-level patterns that previously remained in verbose compiler form:

• Arithmetic and comparison operator methods inlined (op_Addition → +, op_GreaterThan → >, etc.).
• Modulo operator reconstructed from div/mul/sub instruction sequences.
• Boolean short-circuit patterns recognized and simplified.
• Method calls without arguments have parentheses normalized (.Trim → .Trim()).
• Interpolated string handlers (DefaultInterpolatedStringHandler) collapsed into readable string concatenation expressions.

Variable and Structural Cleanup

Beyond individual expressions, the optimizer now cleans up the overall structure of decompiled procedures:

• Orphan return variables eliminated - simple temporaries used only to hold a return value are removed; field access, array access, and method call results are always preserved.
• Redundant condition variable copies removed from loop bodies.
• try/finally/catch blocks preserved and correctly indented.
• foreach scaffolding removed - GetEnumerator, Current, MoveNext, and Dispose calls are stripped once the loop is reconstructed.
• Label-only lines and dead reference comments stripped from output.
• Unreachable goto statements eliminated where the target is the next sequential instruction.

New Plugin: FRX Image Viewer

VB6 applications store embedded resources (images, icons, and cursors) in binary .FRX files alongside each form. Until now, inspecting these assets required external tools or manual hex parsing. Version 26.1 ships with the new FRX Image Viewer plugin that makes this effortless.

The plugin is accessible directly from the Plugins menu and provides:

• Thumbnail preview of all embedded images, icons, and cursors found in the target application.
• Automatic format detection for BMP, PNG, JPEG, GIF, ICO, and CUR resources - no manual configuration needed.
• Multi-resolution icon parsing, so every size variant stored inside a .ICO file is individually accessible.
• One-click export to save any asset to disk in its native format.
• Full dark mode support, consistent with the rest of the VB Decompiler interface.

The plugin's source code is available for free on GitHub:
https://github.com/DotFixSoft/frxviewer

Accessibility and Keyboard Navigation

Version 26.1 brings a comprehensive accessibility overhaul, making VB Decompiler fully usable with NVDA and other screen readers, and significantly more efficient via keyboard alone.

• Project Tree - Enter key support: Pressing Enter on a selected node in the Project Tree now opens the corresponding form, module, or procedure in the active viewer, just as a double-click would.
• New Alt+1 hotkey: Instantly toggles focus between the Project Tree and the currently active view - whether that is the Decompiler/Disassembler code editor, Hex Editor, Form properties panel, or any other pane. This eliminates the need to Tab through every control to switch context.
• Hex Editor Tab navigation fixed: Pressing Tab inside the Hex Editor now correctly cycles between the Hex view and Text view, then cleanly exits the control to the next UI element - previously, focus was trapped inside the editor.
• Screen reader label linking: UI text labels throughout the application are now strictly linked to their corresponding input fields and comboboxes, ensuring screen readers announce the correct context for every control.

Improved .NET IL Opcode Coverage

Version 26.1 extends C# decompilation support to three additional MS IL opcodes: constrained., rem, and rem.un. These opcodes appear in constrained virtual method calls and integer/unsigned remainder operations. They were previously left as raw IL in the output; they are now correctly translated into their C# equivalents.

Stability Fix: Obfuscated .NET Procedures

The internal function responsible for handling local variables in .NET procedures has been completely rewritten. The previous implementation could crash when processing heavily obfuscated files that contain deliberately incorrect local variable declarations - a common anti-decompilation technique. The new implementation handles these edge cases gracefully, eliminating crashes on such files.

Variable Highlighting Improvements

Variable highlighting in the code view has been unified. Previously, clicking a variable highlighted its explicit occurrences but might miss related uses when the variable appeared as part of a structure or object member access. Now, var_XX and str_XX variables are treated identically: clicking any variable highlights all locations where it is used, including as a structure base or object qualifier. For example, clicking str_1 will also highlight str_1.Value.

Bug Fixes

• AI Helper control layout: The position of controls on the AI Helper tab is now correctly adjusted even when the application window size has not changed since the previous launch.
• AI Helper default mode: If the registry contains incorrect or corrupt settings for the AI Helper, the application now safely defaults to LLM mode instead of entering an undefined state.

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