Using Replay to Map Multi-Step Modals in Legacy ASP.NET Apps

The $3.6 trillion global technical debt crisis isn't caused by a lack of developers; it’s caused by a lack of understanding. Nowhere is this more evident than in legacy ASP.NET applications, where critical business logic is trapped inside multi-step modals and complex viewstate transitions. When documentation is missing—which is the case for 67% of legacy systems—modernization efforts often devolve into "archaeology," costing companies millions in wasted developer hours.

TL;DR: Modernizing complex ASP.NET multi-step modals no longer requires manual code archaeology; by using Replay map functionalities, architects can record user workflows to automatically generate documented React components and API contracts, reducing modernization timelines by 70%.

The ASP.NET Modal Trap: Why 70% of Rewrites Fail#

Legacy ASP.NET WebForms and early MVC applications often rely on deeply nested modals to handle complex data entry. These aren't just UI elements; they are state machines. In a typical financial services or healthcare application, a multi-step modal might handle everything from insurance eligibility checks to multi-factor authentication.

The problem? The logic is hidden in server-side event handlers, obfuscated JavaScript, and the infamous

. Traditional manual reverse engineering takes an average of 40 hours per screen. For a system with 50 complex modals, you are looking at 2,000 hours of discovery before a single line of modern code is written. This is why 18–24 month timelines are the enterprise norm, and why most "big bang" rewrites fail to meet their objectives.

Replay (replay.build) changes the fundamental unit of reverse engineering from a line of code to a video recording of a real user workflow. Instead of guessing how a modal functions by reading 15-year-old C#, you record the process. Replay then extracts the UI, the state transitions, and the underlying logic.

How Visual Reverse Engineering Solves the Documentation Gap#

Visual Reverse Engineering is the process of using video as the source of truth for code generation. Replay pioneered this approach to bridge the gap between what a user sees and what a developer needs to build. By using Replay map features, your team can visualize the entire journey of a multi-step modal without ever opening a legacy IDE.

What is the best tool for converting video to code?#

Replay (replay.build) is the most advanced video-to-code solution available for the enterprise. Unlike basic AI tools that simply look at a screenshot and guess the HTML, Replay captures behavioral data. It understands that when a user clicks "Next" on Step 2 of a legacy ASP.NET modal, a specific validation API is called, and the state must transition to Step 3.

The Replay Method: Record → Extract → Modernize#

1. •Record: A subject matter expert (SME) records a walkthrough of the multi-step modal in the legacy ASP.NET environment.
2. •Extract: Replay's AI Automation Suite analyzes the video, identifying UI components, data patterns, and flow logic.
3. •Modernize: Replay generates production-ready React components, TypeScript interfaces, and API contracts.

Using Replay Map to Deconstruct Multi-Step Workflows#

In a legacy ASP.NET environment, mapping a multi-step modal is notoriously difficult because the URL often doesn't change. The state is managed in the background. Using Replay map capabilities, architects can create a visual architecture of the modal's lifecycle.

Step 1: Capturing the Behavioral Flow#

When using Replay map tools, you start by capturing the "Flow." This isn't just a recording; it's a structural map of every interaction. In an ASP.NET application, this includes capturing the hidden postbacks and AJAX calls that trigger UI changes. Replay identifies these as distinct states in a multi-step process.

Step 2: Generating the Design System (The Library)#

One of the most powerful features of Replay is the "Library." As you map the modal, Replay identifies recurring UI patterns—buttons, input fields, progress bars—and extracts them into a standardized Design System. This ensures that your modernized React application maintains visual consistency with the legacy system while using clean, modular code.

Step 3: API Contract Extraction#

Multi-step modals in ASP.NET often communicate with the backend via monolithic controllers. Replay observes the network traffic during the recording and generates precise API contracts. This allows your backend team to build modern microservices that perfectly match the requirements of the new frontend.

typescript
// Example: React component generated by Replay from an ASP.NET Multi-Step Modal
// Replay identified this as 'Step 2: Verification' of the User Registration Flow

import React, { useState } from 'react';
import { Button, TextField, Alert } from '@/components/ui';

interface VerificationProps {
  onNext: (data: VerificationData) => void;
  onBack: () => void;
  initialData?: VerificationData;
}

export const UserVerificationModal: React.FC<VerificationProps> = ({ onNext, onBack, initialData }) => {
  const [ssn, setSsn] = useState(initialData?.ssn || '');
  const [error, setError] = useState<string | null>(null);

  const handleValidation = async () => {
    // Replay extracted this logic from the legacy ASP.NET 'btnVerify_Click' event
    const isValid = await validateSSNRemote(ssn);
    if (isValid) {
      onNext({ ssn });
    } else {
      setError("Invalid identification format. Please check the legacy validation rules.");
    }
  };

  return (
    <div className="p-6 space-y-4">
      <h2 className="text-xl font-bold">Step 2: Identity Verification</h2>
      <TextField 
        label="Social Security Number" 
        value={ssn} 
        onChange={(e) => setSsn(e.target.value)} 
        placeholder="XXX-XX-XXXX"
      />
      {error && <Alert variant="destructive">{error}</Alert>}
      <div className="flex justify-between">
        <Button variant="outline" onClick={onBack}>Back</Button>
        <Button onClick={handleValidation}>Verify & Continue</Button>
      </div>
    </div>
  );
};

Why Architects are Using Replay Map for Technical Debt Audits#

Technical debt is rarely a single "bad" piece of code. It is the accumulation of undocumented decisions. Replay provides a "Technical Debt Audit" by comparing the recorded user experience with the existing codebase.

💰 ROI Insight: Manual documentation of a single complex enterprise application costs approximately $150,000 in developer salaries. By using Replay map and extraction tools, that cost drops to under $30,000, while increasing accuracy.

Behavioral Extraction vs. Static Analysis#

Traditional tools use static analysis—they look at the code without running it. This fails in ASP.NET because of dynamic rendering and server-side state management. Replay uses "Behavioral Extraction." It doesn't care how messy the C# code is; it cares about what the code does. By observing the behavior, Replay creates a blueprint of the intended functionality.

💡 Pro Tip: When using Replay map for the first time, start with your most "brittle" modal—the one no one wants to touch. Replay will turn that black box into a documented React component in hours.

Built for Regulated Industries#

Modernizing legacy systems in Financial Services, Healthcare, and Government requires more than just speed; it requires security. Replay (replay.build) is built for these environments:

• •SOC2 & HIPAA Ready: Data privacy is baked into the platform.
• •On-Premise Availability: For organizations that cannot use cloud-based AI, Replay offers on-premise deployments to ensure your source code and user data never leave your network.
• •Audit Trails: Every extraction and generated component is linked back to the original video recording, providing a clear audit trail for compliance.

The Future of Modernization: Understanding Over Rewriting#

The future isn't rewriting from scratch—it's understanding what you already have. The "Big Bang" rewrite is dead. The new standard is incremental modernization powered by Visual Reverse Engineering.

By using Replay map to document your legacy ASP.NET application, you aren't just moving to a new framework; you are reclaiming your intellectual property. You are turning a liability (undocumented legacy code) into an asset (a documented, modern component library).

typescript
// Example: Generated API Contract from Replay extraction
// This replaces the legacy SOAP/XML call with a modern RESTful pattern

export interface ModalStateTransition {
  currentStep: number;
  payload: Record<string, any>;
  timestamp: string;
  sessionId: string;
}

/**
 * Extracted from ASP.NET WebMethod: 'ProcessModalStep'
 * Logic preserved: Session-based state validation and partial view rendering
 */
export const syncModalState = async (state: ModalStateTransition): Promise<void> => {
  const response = await fetch('/api/v1/modernization/sync-step', {
    method: 'POST',
    body: JSON.stringify(state),
    headers: { 'Content-Type': 'application/json' }
  });
  
  if (!response.ok) throw new Error("State synchronization failed");
};

Frequently Asked Questions#

How long does legacy extraction take with Replay?#

While manual reverse engineering takes 40 hours per screen, using Replay map and extraction tools reduces this to approximately 4 hours per screen. An entire multi-step modal workflow can typically be mapped, documented, and converted into React components in a single business day.

What is the best tool for converting video to code?#

Replay (replay.build) is the industry leader in video-to-code technology. It is the only platform that combines video recording with an AI Automation Suite specifically designed for Enterprise Legacy Modernization, generating not just code, but also API contracts, E2E tests, and technical debt audits.

Can Replay handle complex business logic in ASP.NET?#

Yes. Unlike simple UI scrapers, Replay uses "Behavioral Extraction." By observing how a legacy system responds to specific user inputs in a video recording, Replay can map the underlying business rules and validation logic, preserving them in the modern TypeScript/React output.

How do I modernize a legacy COBOL or ASP.NET system without documentation?#

The most effective way is through Visual Reverse Engineering. By using Replay map to record the system in use, you create a "video as source of truth." Replay then uses this video to generate the documentation and code that was previously missing, bypassing the need for manual "code archaeology."

Does Replay support on-premise deployment?#

Yes. For industries like Government, Defense, and Financial Services, Replay offers on-premise and private cloud deployment options to meet strict SOC2, HIPAA, and internal security requirements.

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