reactive/Rx.NET/Source/System.Reactive.Interfaces/Reactive/IEventPatternSource.cs

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the Apache 2.0 License.
// See the LICENSE file in the project root for more information. 

namespace System.Reactive
{
    /// <summary>
    /// Represents a data stream signaling its elements by means of an event.
    /// </summary>
    /// <typeparam name="TEventArgs">The type of the event data generated by the event.</typeparam>
    public interface IEventPatternSource<TEventArgs>
#if !NO_EVENTARGS_CONSTRAINT
        where TEventArgs : EventArgs
#endif
    {
        /// <summary>
        /// Event signaling the next element in the data stream.
        /// </summary>
        event EventHandler<TEventArgs> OnNext;
    }
}