Solving the VB.net Textbox Value Not Updating in Public Shared Variable

Описание: Discover why your VB.net Textbox value isn't updating a public shared variable, and learn how to fix it with a simple solution.
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This video is based on the question https://stackoverflow.com/q/62545112/ asked by the user 'user1949157' ( https://stackoverflow.com/u/1949157/ ) and on the answer https://stackoverflow.com/a/62545546/ provided by the user 'Idle_Mind' ( https://stackoverflow.com/u/2330053/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the Issue with VB.NET Textbox Value Updates

If you've ever tried to update a public shared variable from a VB.NET textbox and found it returning the default value instead of the expected user input, you're not alone. This problem typically arises when developers misunderstand how and when public shared variables are initialized and updated in their application. In this guide, we'll break down a specific scenario and offer a straightforward solution.

The Scenario

Imagine you have a form that includes a textbox initialized with the text "Hello." You want users to change this text, and upon clicking a button, you expect a message box to display the updated text. However, when you access a public shared variable, it always returns the initial value, "Hello." Let's take a look at the code that creates this issue:

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The Problem Explained

Initialization of Shared Variables

The crux of the problem lies in how shared variables are initialized and updated. In our example, the line:

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

is executed once when the TextField class is first loaded, which means it captures the initial value of the textbox at that moment, which is "Hello." This initialization occurs before the user even sees the form or has a chance to change the textbox's content.

Why the Change Isn't Reflected

Since FieldText is only set once, it does not reflect any subsequent changes made by the user. This is why, even after changing the text in the textbox, accessing TextField.FieldText will still yield the outdated value – the default "Hello."

The Solution: Update on Text Change

The functional solution to this problem lies in utilizing the TextChanged event of the textbox. By updating our public shared variable every time the text in the textbox changes, we can ensure that it always reflects the current user input. Here's how to implement it:

Step-by-Step Fix

Bind to the TextChanged Event: Add an event handler for the textbox's TextChanged event.

Update the Shared Variable: Inside this event handler, update the shared variable to hold the textbox's current value.

Here's how the modified code looks:

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

Updated Class Implementation

Now, integrating this into your existing classes will make them function correctly:

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

With this change, every time the user modifies the textbox's content, the shared variable FieldText will be updated to reflect the new value, providing accurate results when queried later.

Conclusion

Understanding the lifecycle of your variables and the order of events in a VB.NET application is crucial for writing effective code. By reassessing when and how variables are assigned their values, you can avoid issues like the one you've encountered. The solution is both simple and effective, ensuring your application behaves as intended. If you run into similar issues, remember to consider the state of your variables and utilize event handling to keep them updated!