/source/library/Interlace/Binding/ViewConverters/NullConverter.cs

#region Using Directives and Copyright Notice



// Copyright (c) 2007-2010, Computer Consultancy Pty Ltd

// All rights reserved.

// 

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// modification, are permitted provided that the following conditions are met:

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//       notice, this list of conditions and the following disclaimer.

//     * Redistributions in binary form must reproduce the above copyright

//       notice, this list of conditions and the following disclaimer in the

//       documentation and/or other materials provided with the distribution.

//     * Neither the name of the Computer Consultancy Pty Ltd nor the

//       names of its contributors may be used to endorse or promote products

//       derived from this software without specific prior written permission.

// 

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 

// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 

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using System;

using System.Collections.Generic;

using System.Text;

using Interlace.Binding.Views;



#endregion



namespace Interlace.Binding.ViewConverters

{

    public class NullConverter : ViewConverterBase

    {

        bool _negate;



        public NullConverter(bool negate)

        {

            _negate = negate;

        }



        public override object ModelToView(object obj)

        {

            return (obj == null) ^ _negate;

        }



        public override object ViewToModel(object obj)

        {

            throw new InvalidOperationException("A change was made to the view that had an " +

                "attached NullConverter, which is read only.");

        }

    }

}