Casting vs. 'as' in C#: When Should I Use Which?

C# forced type conversion and

Keywords: When will it be used? as

When processing the interface, it is often encountered in the case of type conversion. The two commonly used methods are compulsory type conversion and use of

keywords. Understanding the difference between these two methods is essential for effective code optimization and error prevention. as

Forced type conversion and

keyword as

Compulsory type conversion (explicit conversion)

: The compulsory type conversion involves explicitly converting the type of the object into the required type. It uses grammar, where represents the target type. (Type) Type Keywords (hidden conversion)

:

Keyword attempts to convert the object into a compatible type. If the conversion is unsuccessful, it will return . The grammar is as, where also represents the target type. as null cost and performance effects object as Type Type The modern instant (JIT) compiler will optimize the compulsory type conversion and

conversion, and in most cases, the same performance can be obtained. However, in some cases, if the conversion is invalid, the compulsory type conversion may cause abnormalities during runtime, which may cause minor performance loss.

The preferred method and usage scenario

as Use forced type conversion for:

Make sure specific conversion: Mandatory type conversion can ensure the successful conversion because it causes abnormalities when the conversion is invalid. Treatment abnormality: By capturing abnormalities caused by the conversion of mandatory types, developers can handle the types that do not match and ensure correct errors.

• Use
Keywords for:

Convert to empty type: When using the type of empty type (such as , as), keywords are particularly useful. If the conversion is unsuccessful, it will return

to avoid potential mistakes.

• Check type compatibility: bool? Keywords allow high -efficiency to check type compatibility without causing abnormalities. int? as null code example
• as In this example, the compulsory type conversion ensures that
is an effective

instance, and

keyword attempts to conversion, if it fails, return

. If the interface references to change the type at runtime, the compulsory type conversion will cause abnormalities, and

public interface IMyInterface
{
    void AMethod();
}

public class MyClass : IMyInterface
{
    public void AMethod() { /* Implementation */ }
}

public class Implementation
{
    IMyInterface _myInterface;
    MyClass _myClass1;
    MyClass _myClass2;

    public Implementation()
    {
        _myInterface = new MyClass();

        _myClass1 = (MyClass)_myInterface;   // 强制类型转换
        _myClass2 = _myInterface as MyClass; // 'as' 关键字
    }
}

keywords will return elegantly

. _myClass1 MyClass Conclusion as Mandatory type conversion and null The selection of keywords depends on specific usage scenarios. The compulsory type conversion provides certainty and abnormal treatment, and _myInterface keywords are more suitable for empty types and type compatibility checks. In most cases, modern JIT compilers will optimize these two methods to obtain the same performance, eliminating concerns about major performance losses. as

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