Extracting UI Components from Silverlight: A Final Solution for the Sunset Problem

Silverlight isn't just a legacy framework; it’s a security liability holding billions of dollars in enterprise value hostage. For years, financial institutions and healthcare providers have kept "zombie" VMs alive just to run critical line-of-business applications that depend on a plugin Microsoft killed in 2021. The $3.6 trillion global technical debt isn't a theoretical problem—it's the reality of a VP of Engineering staring at a 24-month rewrite estimate for a system that no one currently employed even understands.

The "Big Bang" rewrite is a proven failure, with 70% of legacy modernizations exceeding their timelines or failing entirely. The bottleneck isn't writing new code; it's the "archaeology" of rediscovering business logic buried in 15-year-old XAML files and C# code-behind.

TL;DR: Extracting UI components from Silverlight via visual reverse engineering reduces modernization timelines from years to weeks by using video as the source of truth for generating documented React components.

The Silverlight Modernization Crisis#

Most enterprise Silverlight applications were built between 2008 and 2014. These systems are characterized by deep nesting, complex data grids, and stateful workflows that are poorly documented. 67% of these legacy systems lack any meaningful documentation, leaving architects to guess at the original intent of the UI logic.

When you attempt to migrate these systems, you face three primary hurdles:

1. •Browser Incompatibility: Silverlight requires Internet Explorer or specialized "IE Mode" wrappers, creating massive security holes.
2. •Proprietary XAML Logic: Silverlight’s flavor of XAML (Extensible Application Markup Language) doesn't map 1:1 to modern HTML5/CSS3.
3. •The "Black Box" Effect: The original developers are gone. The source code, if it exists, is often a tangled mess of MVVM patterns that have shifted over a decade of hotfixes.

Modernization Strategy Comparison#

Why Manual Extraction Fails#

The industry average for manual extraction—manually inspecting a Silverlight screen, documenting the fields, identifying the API calls, and recreating the component in React—is roughly 40 hours per complex screen. In a typical enterprise app with 50+ screens, you're looking at a year of development before you even reach MVP.

⚠️ Warning: Manual rewrites often lead to "feature drift," where the new system lacks subtle but critical business rules present in the legacy UI, leading to user rejection and costly post-launch fixes.

Replay changes this math. By recording a real user workflow, Replay’s engine identifies the UI boundaries, state changes, and data requirements, reducing that 40-hour window to just 4 hours.

Technical Deep Dive: From XAML to React#

Extracting UI components requires more than just scraping pixels. It requires understanding the underlying intent. Silverlight relied heavily on

controls, , and complex expressions.

The Legacy XAML (The Problem)#

xml
<!-- Typical Silverlight Data Entry Fragment -->
<sdk:DataGrid x:Name="OrderGrid" AutoGenerateColumns="False" ItemsSource="{Binding Orders}">
    <sdk:DataGrid.Columns>
        <sdk:DataGridTextColumn Header="Order ID" Binding="{Binding OrderID}" />
        <sdk:DataGridTemplateColumn Header="Status">
            <sdk:DataGridTemplateColumn.CellTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Status}" Foreground="{Binding Status, Converter={StaticResource StatusToBrushConverter}}" />
                </DataTemplate>
            </sdk:DataGridTemplateColumn.CellTemplate>
        </sdk:DataGridTemplateColumn>
    </sdk:DataGrid.Columns>
</sdk:DataGrid>

The Extracted React Component (The Solution)#

When Replay processes a workflow involving the grid above, it doesn't just look at the code; it looks at the rendered output and interaction model. It generates a clean, functional React component using your organization's design system.

typescript
// Generated by Replay AI Automation Suite
import React from 'react';
import { DataGrid, StatusBadge } from '@/components/ui';
import { useOrders } from '@/hooks/api';

interface Order {
  id: string;
  status: 'Pending' | 'Completed' | 'Delayed';
}

export const OrderManagement: React.FC = () => {
  const { data: orders, isLoading } = useOrders();

  const columns = [
    { header: 'Order ID', accessor: 'id' },
    { 
      header: 'Status', 
      accessor: 'status',
      cell: (row: Order) => <StatusBadge type={row.status} /> 
    }
  ];

  if (isLoading) return <SkeletonGrid />;

  return (
    <div className="p-6">
      <h2 className="text-2xl font-bold mb-4">Order Management</h2>
      <DataGrid data={orders} columns={columns} />
    </div>
  );
};

💡 Pro Tip: Don't try to port Silverlight's

text

ValueConverters

directly. Instead, use Replay to extract the visual state transitions and map them to modern CSS-in-JS or Tailwind utility classes.

The Replay Workflow: 4 Steps to Modernization#

Step 1: Recording the Source of Truth#

Instead of digging through old

files, a subject matter expert (SME) records a session of the legacy application in action. This video serves as the "Source of Truth." Replay captures not just the video, but the DOM structure (if web-based) or the visual hierarchy.

Step 2: Visual Reverse Engineering#

Replay’s engine analyzes the recording. It identifies repeating patterns—buttons, inputs, grids, and navigation elements. It maps these to a centralized Library (Design System). This ensures that if you have 100 screens with the same "Submit" button logic, they are consolidated into a single React component.

Step 3: Blueprint Generation#

Using the Blueprints (Editor), architects can refine the extracted components. This is where you define your API Contracts. If the Silverlight app called a SOAP service, Replay helps you define the modern REST or GraphQL equivalent.

Step 4: Code Generation and E2E Testing#

Replay generates the React code, TypeScript interfaces, and—crucially—E2E Tests. Because Replay knows exactly how the user interacted with the legacy system, it can generate Playwright or Cypress tests that ensure the new component behaves identically to the old one.

💰 ROI Insight: By automating the documentation and initial component scaffolding, enterprises typically see a 70% reduction in engineering hours. For a 20-screen migration, this translates to a savings of approximately $180,000 in developer salaries alone.

Handling Complex Business Logic#

The biggest fear in extracting UI components is losing the hidden business logic—the "if this field is X, then disable field Y" rules. In Silverlight, this was often buried in C# ViewModels or hidden in

groups.

Replay's Flows (Architecture) feature maps these state transitions. By observing the UI's reaction to user input during the recording, Replay identifies the logic gates.

Example: Preserving State Logic#

If a Silverlight form disables a "Submit" button until a "Tax ID" matches a specific regex, Replay flags this behavior.

typescript
// Replay-generated validation logic preserved from legacy workflow
export function useTaxValidation(taxId: string) {
  const isValid = React.useMemo(() => {
    // Logic extracted from observed legacy behavior
    const pattern = /^[0-9]{2}-[0-9]{7}$/;
    return pattern.test(taxId);
  }, [taxId]);

  return isValid;
}

Built for Regulated Environments#

We understand that Silverlight apps are most common in Financial Services, Healthcare, and Government—sectors where security is non-negotiable.

• •SOC2 & HIPAA Ready: Replay’s infrastructure is built to handle sensitive data.
• •On-Premise Available: For air-gapped environments or strict data sovereignty requirements, Replay can be deployed entirely within your firewall.
• •Technical Debt Audit: Every extraction includes a full audit of what was moved, what was consolidated, and what was deprecated.

📝 Note: Unlike "low-code" platforms that lock you into a proprietary runtime, Replay generates standard React/TypeScript code that your team owns and maintains forever.

The Future Isn't Rewriting—It's Understanding#

The "Big Bang" rewrite is a relic of an era when we had more time and fewer security threats. Today, the 18-month average enterprise rewrite timeline is a death sentence for agility.

By extracting UI components visually, you bypass the "archaeology" phase. You move directly from a black box to a documented, modern codebase. You don't just get a new UI; you get a design system, API contracts, and a deep understanding of your own business logic that was lost a decade ago.

Frequently Asked Questions#

How long does legacy extraction take with Replay?#

While a manual rewrite takes 18-24 months, Replay typically completes the extraction and initial component generation phase in 2-8 weeks. This allows your team to focus on integration and refinement rather than basic scaffolding.

What about business logic preservation?#

Replay uses visual state analysis to identify logic gates. By observing how the UI responds to different inputs during the recording phase, we can generate functional logic that mirrors the legacy system's behavior, which is then verified against the original source code where available.

Does Replay require access to our original source code?#

No. While having the source code can provide additional context for the AI Automation Suite, Replay's primary "Source of Truth" is the visual recording of the application in use. This makes it ideal for systems where the source code is lost, corrupted, or too messy to be useful.

Can we export the code to our own framework?#

Yes. Replay generates clean React components, TypeScript definitions, and CSS (or Tailwind). There is no vendor lock-in; the code generated is yours to keep and modify in your own CI/CD pipeline.

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Ready to modernize without rewriting? Book a pilot with Replay - see your legacy screen extracted live during the call.