BindingSourceValueProvider.cs

// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

using System;
using Microsoft.AspNetCore.Mvc.Core;

namespace Microsoft.AspNetCore.Mvc.ModelBinding
{
    /// <summary>
    /// A value provider which provides data from a specific <see cref="BindingSource"/>.
    /// </summary>
    /// <remarks>
    /// <para>
    /// A <see cref="BindingSourceValueProvider"/> is an <see cref="IValueProvider"/> base-implementation which
    /// can provide data for all parameters and model properties which specify the corresponding
    /// <see cref="ModelBinding.BindingSource"/>.
    /// </para>
    /// <para>
    /// <see cref="BindingSourceValueProvider"/> implements <see cref="IBindingSourceValueProvider"/> and will
    /// include or exclude itself from the set of value providers based on the model's associated
    /// <see cref="ModelBinding.BindingSource"/>. Value providers are by-default included; if a model does not
    /// specify a <see cref="ModelBinding.BindingSource"/> then all value providers are valid.
    /// </para>
    /// </remarks>
    public abstract class BindingSourceValueProvider : IBindingSourceValueProvider
    {
        /// <summary>
        /// Creates a new <see cref="BindingSourceValueProvider"/>.
        /// </summary>
        /// <param name="bindingSource">
        /// The <see cref="ModelBinding.BindingSource"/>. Must be a single-source (non-composite) with
        /// <see cref="ModelBinding.BindingSource.IsGreedy"/> equal to <c>false</c>.
        /// </param>
        public BindingSourceValueProvider(BindingSource bindingSource)
        {
            if (bindingSource == null)
            {
                throw new ArgumentNullException(nameof(bindingSource));
            }

            if (bindingSource.IsGreedy)
            {
                var message = Resources.FormatBindingSource_CannotBeGreedy(
                    bindingSource.DisplayName,
                    nameof(BindingSourceValueProvider));
                throw new ArgumentException(message, nameof(bindingSource));
            }

            if (bindingSource is CompositeBindingSource)
            {
                var message = Resources.FormatBindingSource_CannotBeComposite(
                    bindingSource.DisplayName,
                    nameof(BindingSourceValueProvider));
                throw new ArgumentException(message, nameof(bindingSource));
            }

            BindingSource = bindingSource;
        }

        /// <summary>
        /// Gets the corresponding <see cref="ModelBinding.BindingSource"/>.
        /// </summary>
        protected BindingSource BindingSource { get; }

        /// <inheritdoc />
        public abstract bool ContainsPrefix(string prefix);

        /// <inheritdoc />
        public abstract ValueProviderResult GetValue(string key);

        /// <inheritdoc />
        public virtual IValueProvider Filter(BindingSource bindingSource)
        {
            if (bindingSource == null)
            {
                throw new ArgumentNullException(nameof(bindingSource));
            }

            if (bindingSource.CanAcceptDataFrom(BindingSource))
            {
                return this;
            }
            else
            {
                return null;
            }
        }
    }
}