new Constraint (C# Reference)

The new constraint specifies that any type argument in a generic class declaration must have a public parameterless constructor. To use the new constraint, the type cannot be abstract.

Example

Apply the new 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();
    }
}

Example

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

public class ItemFactory2<T>
    where T : IComparable, new()
{
}

For more information, see Constraints on Type Parameters.

C# Language Specification

For more information, see the C# Language Specification. The language specification is the definitive source for C# syntax and usage.

See Also

System.Collections.Generic
C# Reference
C# Programming Guide
C# Keywords
Operator Keywords
Generics