Can Generic Type Instantiation Handle Constructor Arguments in C#?

C# generic type instantiation and constructor parameters

When building a generic type, a common question is: How to instantiate a constructor that requires parameters in a generic method? For example, the BaseFruit class has a constructor that receives a weight parameter of type integer.

How to instantiate fruits with a specified weight in a generic method?

The following code attempts to create a fruit instance with a specified weight in a generic method:

<code class="language-csharp">public void AddFruit<T>() where T : BaseFruit
{
    BaseFruit fruit = new T(weight); /*new Apple(150);*/
    fruit.Enlist(fruitManager);
}</code>

This approach is only possible if BaseFruit has a parameterless constructor that subsequently modifies the properties via member variables. However, in real applications, this may not be practical.

Alternative:

can use the Activator class:

<code class="language-csharp">return (T)Activator.CreateInstance(typeof(T), new object[] { weight });</code>

In this case, the T constraint on new() ensures that a public parameterless constructor exists at compile time, and the Activator class is responsible for the actual type creation.

Note:

While this scenario provides a workaround, the existence of the specific constructor must be verified in the code. Additionally, relying on this approach may indicate a problem at the code level and should be avoided in current versions of C#.

The above is the detailed content of Can Generic Type Instantiation Handle Constructor Arguments in C#?. For more information, please follow other related articles on the PHP Chinese website!