C# – generic constructor with parameter constraint in C#

cconstructorgeneric-constraintsgenericsparameters

In C# you can put a constraint on a generic method like:

public class A {

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

}

Where you specify that T should have a constructor that requires no parameters. I'm wondering whether there is a way to add a constraint like "there exists a constructor with a float[,] parameter?"

The following code doesn't compile:

public class A {

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

}

A workaround is also useful?

Best Answer

As you've found, you can't do this.

As a workaround I normally supply a delegate that can create objects of type T:

public class A {

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

}

Related Solutions

C# – Calling the base constructor in C#

Modify your constructor to the following so that it calls the base class constructor properly:

public class MyExceptionClass : Exception
{
    public MyExceptionClass(string message, string extrainfo) : base(message)
    {
        //other stuff here
    }
}

Note that a constructor is not something that you can call anytime within a method. That's the reason you're getting errors in your call in the constructor body.

C# – Create Generic method constraining T to an Enum

Since Enum Type implements IConvertible interface, a better implementation should be something like this:

public T GetEnumFromString<T>(string value) where T : struct, IConvertible
{
   if (!typeof(T).IsEnum) 
   {
      throw new ArgumentException("T must be an enumerated type");
   }

   //...
}

This will still permit passing of value types implementing IConvertible. The chances are rare though.

Best Answer

Related Solutions

C# – Calling the base constructor in C#

C# – Create Generic method constraining T to an Enum

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