Скачать или смотреть How to Pass a Parameter by ref to a Member Variable in C#

A beginner's guide to understanding how to pass parameters by reference in C# . Get practical insights and examples to avoid common pitfalls.
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Understanding Parameters in C# : Passing by Reference vs. Passing by Value

As a newcomer to C# , especially with a background in C+ + , it's common to encounter challenges while transitioning from the familiar concepts of pointers to references. One question that often arises is: How do I pass a parameter by ref to a member variable? In this guide, we’ll explore this issue in-depth and provide clear solutions to prevent common pitfalls, like encountering a null exception.

The Problem

You might find yourself in a situation where you have a class, let's call it EColour, and you're trying to pass a reference of ICellTemplate to a member variable m_template. Despite your best intentions, you may discover that m_template is unexpectedly null during an event handler, leading to frustrating null reference exceptions. Here's the essential piece of code causing the confusion:

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When you attempt to access m_template later, an exception is thrown because it has turned out to be null.

Understanding Types in C#

Before diving into solutions, it’s crucial to clarify how C# handles different data types:

Value Types: These include all primitive types such as int, float, double, etc. When passed, a copy of the value is made.

Reference Types: These include all classes that inherit from object, such as ICellTemplate. When passed, the reference to the original object is sent, enabling access to its properties and methods.

The Solution

The key to fixing the null reference issue lies in how you handle the ICellTemplate parameter. Instead of using ref, pass it as a regular argument. Here’s how to redefine the constructor:

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Why This Works

When you pass ICellTemplate without ref, you’re effectively passing the reference to the object that cellTemplate points to. This means your m_template will have the same reference, and you’ll avoid creating confusion that can lead to dereferencing a null object.

Summary

In conclusion, while transitioning from C+ + to C# , it’s important to understand the difference between passing by reference and passing by value. For reference types, use regular parameter passing instead of ref unless necessary, so you can correctly manage your member variables.

Key Takeaways:

Use regular parameter passing for reference types to keep references intact.

Understand the distinction between value types and reference types, as it helps in avoiding common pitfalls related to null values.

Address any potential null reference issues proactively by ensuring the initialization of your member variables.

By following these guidelines, you can build more robust and error-free C# applications. Happy coding!