Something guaranteed not to be null, opposite of Nullable<T>

NotNullable.cs

using System;
using System.Diagnostics.Contracts;

public struct NonNullable<T> where T : class
{
    private readonly T data;

    public NonNullable(T data)
    {
        if (data == null)
        {
            throw new ArgumentNullException("data");
        }

        this.data = data;
    }

    public T Data
    {
        get
        {
            Contract.Ensures(Contract.Result<T>() != null);
            return this.data;
        }
    }

    [ContractInvariantMethod]
    private void ObjectInvariant()
    {
        Contract.Invariant(this.data != null);
    }
}