Resolving Symbolic References in a CodeDOM (Part 7)

// The Nova Project by Ken Beckett.
// Copyright (C) 2007-2012 Inevitable Software, all rights reserved.
// Released under the Common Development and Distribution License, CDDL-1.0: http://opensource.org/licenses/cddl1.php

using System.Linq;
using System.Reflection;

namespace Nova.Utilities
{
    /// <summary>
    /// Static helper methods for <see cref="ParameterInfo"/>.
    /// </summary>
    public static class ParameterInfoUtil
    {
        #region /* STATIC HELPER METHODS */

        /// <summary>
        /// The name of the 'params' attribute.
        /// </summary>
        public const string ParamArrayAttributeName = "ParamArrayAttribute";

        /// <summary>
        /// Check if the ParameterInfo has the 'params' modifier.
        /// </summary>
        public static bool IsParams(ParameterInfo parameterInfo)
        {
            return HasCustomAttribute(parameterInfo, ParamArrayAttributeName);
        }

        /// <summary>
        /// Check if the ParameterInfo has the 'ref' modifier.
        /// </summary>
        public static bool IsRef(ParameterInfo parameterInfo)
        {
            // A 'ref' will generally NOT have the "[In]" and "[Out]" attributes, so assume 'ref' for an IsByRef type where
            // the parameter is NOT an 'out'.
            return (parameterInfo.ParameterType.IsByRef && !(parameterInfo.IsOut && !parameterInfo.IsIn));
        }

        /// <summary>
        /// Check if the ParameterInfo has the 'out' modifier.
        /// </summary>
        public static bool IsOut(ParameterInfo parameterInfo)
        {
            // The IsIn and IsOut properties reflect the "[In]" and "[Out]" attributes, NOT the C# 'ref' and 'out' keywords.
            // An 'out' parameter will always have an IsByRef type, and should always have the "[Out]" attribute to distinguish
            // it from a 'ref'.  To be thorough, also ensure that there isn't an "[In]" attribute.
            return (parameterInfo.ParameterType.IsByRef && parameterInfo.IsOut && !parameterInfo.IsIn);
        }

        /// <summary>
        /// Determine if a ParameterInfo has a custom attribute.
        /// </summary>
        /// <remarks>
        /// This method must be used instead of the built-in GetCustomAttributes() call when working with
        /// members of reflection-only assemblies (otherwise, the custom attribute type would be instantiated,
        /// which is illegal).
        /// </remarks>
        public static bool HasCustomAttribute(ParameterInfo parameterInfo, string name)
        {
            return Enumerable.Any(CustomAttributeData.GetCustomAttributes(parameterInfo),
                delegate(CustomAttributeData customAttribute) { return customAttribute.Constructor.DeclaringType != null && customAttribute.Constructor.DeclaringType.Name == name; });
        }

        /// <summary>
        /// Get the category name.
        /// </summary>
        public static string GetCategory(ParameterInfo parameterInfo)
        {
            return "parameter";
        }

        #endregion
    }
}