Скачать или смотреть Blazor: How to Call a Method on Property Value Change

Learn how to effectively invoke a method in Blazor when a property value changes—automatically, without user interference.
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How to Call a Method on Property Value Change in Blazor

If you're working with Blazor and need to call a method whenever a property value changes—specifically when the change is not triggered by user actions—you've come to the right place! This type of functionality can be essential when you want to react to data changes in your application without direct user input. In this post, we'll explore how to implement this in a straightforward way.

Understanding the Problem

Let's take a look at a sample property in Blazor:

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The Challenge

The challenge is to invoke a method whenever the SelectedPatientId changes. However, the change we are interested in shouldn't be a result of user actions (like input events). For instance, if another part of your application updates the patient ID programmatically, you want to respond accordingly.

What You've Tried

You may have attempted to bind the property to an input element or handle the onchange event like so:

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Unfortunately, these approaches will not trigger the desired behavior when the value changes programmatically because they are designed to respond only to user interactions.

The Solution

Using Property Setters

A more effective solution involves using property setters. This way, you can execute any logic (like calling a method) every time the property is set, regardless of how the change occurred. Here’s how to do it:

Define a Backing Field: You will start by defining a backing field to hold the actual value.

Implement the Getter and Setter: In the setter, you will call your method whenever the property is changed.

Here's an example of how you can implement this in your Blazor component:

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Defining the Value Changed Method

It is essential to ensure that your method handles tasks properly, especially since it may involve asynchronous operations. Keep in mind that an asynchronous method in C# should return either Task or ValueTask, not void. Here is how you might structure the valuechanged method:

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Important Considerations

Return Type: Remember that the return type of your valuechanged() method should be Task to follow the asynchronous programming model correctly. This allows any calling function to await it, promoting better performance and responsiveness in your application.

Clean Code Practices: It’s essential to adopt clean code practices, such as maintaining clear method names and handling exceptions that may occur in asynchronous operations.

Conclusion

By utilizing property setters in Blazor, you can easily invoke methods seamlessly whenever a property value changes. This approach not only keeps your code organized but also enhances the responsiveness of your application. Now, you can confidently implement such features in your Blazor applications without worrying about user-induced changes. Happy coding!