Can C# Generic Methods Constrain Type Parameters to Specific Constructors?

Constructor constraints with parameter specification in C#

In C#, generic methods allow constraints to be imposed on type parameters. For example, the following code shows a constraint that requires parameter type T to have a parameterless constructor:

<code class="language-csharp">public class A {

    public static T Method<T>(T a) where T : new() {
        //...do something...
        return new T();
    }

}</code>

This begs the question: can we refine the constraints and specify that T should have a constructor that accepts a float[,] argument? Unfortunately, the following attempt fails to compile:

<code class="language-csharp">public class A {

    public static T Method<T>(T a) where T : new(float[,] u) {
        //...do something...
        return new T(new float[0,0]);
    }

}</code>

Solution

Since this constraint cannot be used, we can adopt a workaround and use a delegate to initialize an object of type T:

<code class="language-csharp">public class A {

    public static void Method<T>(T a, Func<float[,], T> creator) {
        //...do something...
    }

}</code>

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