csharp/src/ProtocolBuffers/FieldAccess/IFieldAccessor.cs

#region Copyright notice and license
// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.  All rights reserved.
// https://developers.google.com/protocol-buffers/
//
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//
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// in the documentation and/or other materials provided with the
// distribution.
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// contributors may be used to endorse or promote products derived from
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//
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#endregion

namespace Google.Protobuf.FieldAccess
{
    /// <summary>
    /// Allows fields to be reflectively accessed in a smart manner.
    /// The property descriptors for each field are created once and then cached.
    /// In addition, this interface holds knowledge of repeated fields, builders etc.
    /// </summary>
    internal interface IFieldAccessor<T> where T : IMessage<T>
    {
        /// <summary>
        /// Indicates whether the specified message contains the field. For primitive fields
        /// declared in proto3-syntax messages, this simply checks whether the value is the default one.
        /// </summary>
        /// <exception cref="InvalidOperationException">The field is a repeated field, or a single primitive field.</exception>
        bool HasValue(T message);

        /// <summary>
        /// Clears the field in the specified message. (For repeated fields,
        /// this clears the list.)
        /// </summary>
        void Clear(T message);

        /// <summary>
        /// Fetches the field value. For repeated values, this will be an
        /// <see cref="IList"/> implementation.
        /// </summary>
        object GetValue(T message);

        /// <summary>
        /// Mutator for single fields only. (Repeated fields must be mutated
        /// by fetching the list, then mutating that.)
        /// </summary>
        /// <exception cref="InvalidOperationException">The field is a repeated field.</exception>
        void SetValue(T message, object value);
    }
}