.NET  

ScopedValueChanger<T> - A very helpful Generic Helper Class to Temporary Change Values

Overview

Managing temporary changes in software development can be challenging, especially in situations where reverting to the original state is crucial once the changed state is no longer needed. The ScopedValueChanger<T> class in .NET provides a structured and reliable way to handle temporary value modifications. This class ensures that a value is altered for the duration of a particular scope and reliably restored to its original state when the operation is complete.

Design and Functionality

The ScopedValueChanger<T> implements the IDisposable interface, capitalizing on the powerful dispose pattern in .NET to automatically reset the affected value once the instance goes out of scope. Here are the key features and functioning of the ScopedValueChanger<T> class:

Structure

  • Type Parameter T: The class is generic with a type parameter T, allowing it to be used with any data type. This provides flexibility in handling various types of properties or fields.

  • Constructor Parameters:

    • Func<T> getter: A function to retrieve the current value.
    • Action<T> setter: An action to set the value.
    • T newValue: The new value to be temporarily set.

Behavior

Upon instantiation, the ScopedValueChanger records the current value through the getter delegate and apply the newValue using the setter delegate. When the Dispose method is called—either explicitly or at the end of a using block—the value is reverted to its original state, ensuring state consistency.

Exception Handling

The constructor throws an ArgumentNullException if either the getter or setter is null, preventing undefined behavior from invalid arguments.

Practical Use Cases

The ScopedValueChanger<T> is quite versatile and can be employed in various scenarios. Here are some examples:

Example 1. Temporarily Modifying a Global Setting

Imagine a scenario where an application has a global setting controlling whether logging is enabled. In certain sections of code, such as during performance-sensitive operations, it might be beneficial to temporarily disable logging:

using (var changer = new ScopedValueChanger<bool>(() => Logger.IsEnabled, v => Logger.IsEnabled = v, false))
{
    // Perform operations without logging.
}
// The logging state is automatically restored here.

Example 2. UI Element Visibility

In UI applications, it might be necessary to hide certain elements temporarily, for instance, during a screen transition:

UIElement myPanel = FindPanel();
using (var changer = new ScopedValueChanger<bool>(() => myPanel.IsVisible, v => myPanel.IsVisible = v, false))
{
    // Perform UI updates without the panel being visible.
}
// Panel visibility is restored automatically.

Example 3. Database Transactions

While handling database transactions, it is crucial to ensure that parameters like connection strings or cache settings are accurately restored post-transaction to maintain integrity:

string currentConnectionString = Database.ConnectionString;
using (var changer = new ScopedValueChanger<string>(() => Database.ConnectionString, s => Database.ConnectionString = s, "TemporaryConnection"))
{
    // Perform database operations using the temporary connection string.
}
// The original connection string is restored automatically.

Conclusion

The ScopedValueChanger<T> class is an excellent utility for managing temporary alterations, specifically in contexts requiring resource cleanup or state management. Its reliance on the dispose pattern underscores both safety and simplicity in handling such operations, providing developers with an effective tool for maintaining application integrity across diverse application scenarios.

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