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new Constraint (C# Reference)

The new constraint specifies that any type argument in a generic class declaration must have a public parameterless constructor. Apply this constraint to a type parameter when your generic class creates new instances of the type, as shown in the following example:

class ItemFactory<T> where T : new()
    public T GetNewItem()
        return new T();

When you use the new() constraint with other constraints, it must be specified last:

using System;
public class ItemFactory<T>
    where T : IComparable, new()

For more information , see Constraints on Type Parameters (C# Programming Guide).

For more information, see the following sections in the C# Language Specification:

  • 19.1.4 Constraints