How to Effectively Loop Inside a Switch Statement in C# for User Input Validation

Learn how to implement user input validation using loops within switch statements in C-. This guide offers a clear approach to handle inputs for your BMI calculator, improving user interaction.
---
This video is based on the question https://stackoverflow.com/q/69839226/ asked by the user 'Jjstar' ( https://stackoverflow.com/u/17327757/ ) and on the answer https://stackoverflow.com/a/69839327/ provided by the user 'Dmitry Bychenko' ( https://stackoverflow.com/u/2319407/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: attempting to loop inside a switch

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/licensing
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
How to Effectively Loop Inside a Switch Statement in C- for User Input Validation

Developing software that interacts with users can be a bit tricky, especially when it comes to accepting valid input. A common issue arises when trying to loop back inside a switch statement for input validation. This guide will tackle a common challenge faced by beginners—looping through user prompts for a BMI calculator until valid input is provided.

The Challenge

Imagine you are building a simple BMI (Body Mass Index) calculator in C-. The application requires users to input their height in meters and weight in kilograms. However, if users enter invalid values (like a string instead of a number), the program should inform them of the error and prompt them to try again.

The original attempt involved a switch statement with goto to loop back on errors. While this gets the job done, it's not considered best practice due to its potential for creating messy and hard-to-read code.

Example Situation:

You may have a switch statement as shown below:

[[See Video to Reveal this Text or Code Snippet]]

The challenge is making sure that the user enters valid values for both their height and weight before proceeding to calculate the BMI.

The Solution: Method Extraction for Input Validation

To enhance user experience and keep your code organized, we can employ a technique called method extraction. This technique allows us to separate the logic for reading input and validating it into its own method. By doing so, we can easily reuse this method whenever we need to get validated user input.

Step 1: Creating the Input Validation Method

Here’s how you can define a method that repeatedly prompts the user until a valid double value is entered:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Using the Method in Your Switch Statement

Now that we have a method to read and validate user input, we can use it in our switch case:

[[See Video to Reveal this Text or Code Snippet]]

Key Highlights:

Clear User Prompts: By utilizing the ReadDouble method, your prompts will always ask for the correct input, thus improving user interaction.

Reusable Logic: The validation logic is now centralized in one method that can be reused throughout your application whenever input is required.

Simplified Code: The overall structure of your switch case becomes much neater and easier to read, avoiding the pitfalls of using goto.

Conclusion

Using a method extraction strategy not only enhances the readability of your code but also improves the user experience by providing consistent validation for input. This approach is especially useful when developing applications that require user inputs, such as a BMI calculator or any similar application.

By following the best practices outlined in this post, you're well on your way to creating clean, efficient, and user-friendly C- applications.