Linq Reflection : Expression « LINQ « C# / C Sharp

1. C# / C Sharp
2. LINQ
3. Expression

Linq Reflection

        

using System;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;

namespace WindowsPhoneMvp.Util
{
    public class Property
    {
        /// <summary>
        /// Returns the string name of a property, this allows type / member safety
        /// </summary>
        /// <param name="propertyNameLambda">() => obj.Name</param>
        /// <returns>Name</returns>
        public static string GetFor(Expression<Func<object>> propertyNameLambda)
        {
            MemberExpression member;
            if(propertyNameLambda.Body is UnaryExpression)
                member = ((UnaryExpression)propertyNameLambda.Body).Operand as MemberExpression;
            else
                member = propertyNameLambda.Body as MemberExpression;
            if (member != null)
                return member.Member.Name;
            throw new ArgumentException("Could not determine property name.", "propertyNameLambda");
        }

        public static string[] GetFor(params Expression<Func<object>>[] propertyNameLambda)
        {
            return propertyNameLambda
                .Select(property => property.Body)
                .OfType<MemberExpression>()
                .Select(member => member.Member.Name)
                .Concat(propertyNameLambda
                    .Select(property => property.Body)
                    .OfType<UnaryExpression>()
                    .Select(member => member.Operand)
                    .OfType<MemberExpression>()
                    .Select(member => member.Member.Name))
                .ToArray();
        }

        /// <summary>
        /// Returns the string name of a property, this allows type / member safety
        /// </summary>
        /// <typeparam name="T">Type of objects who's properties to evaluate</typeparam>
        /// <param name="propertyNameLambda">obj => obj.Name</param>
        /// <returns>Name</returns>
        public static string For<T>(Expression<Func<T, object>> propertyNameLambda)
        {
            var memberInfo = GetMemberInfo(propertyNameLambda);
            if(memberInfo != null)
                return memberInfo.Name;
            throw new ArgumentException("Could not determine property name.", "propertyNameLambda");
        }

        /// <summary>
        /// Returns the string name of a property, this allows type / member safety
        /// </summary>
        /// <remarks> 
        /// Adding the TRetVal parameter allows more efficient Lambda expressions (doesn't create the Convert(p => p.ID) function)
        /// also helps in Generic Type inference
        /// </remarks>
        public static string For<T, TRetVal>(Expression<Func<T, TRetVal>> propertyNameLambda)
        {
            var memberInfo = GetMemberInfo(propertyNameLambda);
            if(memberInfo != null)
                return memberInfo.Name;
            throw new ArgumentException("Could not determine property name.", "propertyNameLambda");
        }

        static MemberInfo GetMemberInfo<T, TRetVal>(Expression<Func<T, TRetVal>> propertyNameLambda)
        {
            MemberExpression member;
            if(propertyNameLambda.Body is UnaryExpression)
                member = ((UnaryExpression)propertyNameLambda.Body).Operand as MemberExpression;
            else
                member = propertyNameLambda.Body as MemberExpression;
            return member != null ? member.Member : null;
        }

        public static PropertyInfo InfoFor<T>(Expression<Func<T, object>> propertyNameLambda)
        {
            MemberExpression member;
            if (propertyNameLambda.Body is UnaryExpression)
                member = ((UnaryExpression)propertyNameLambda.Body).Operand as MemberExpression;
            else
                member = propertyNameLambda.Body as MemberExpression;
            if (member != null)
            {
                return member.Member as PropertyInfo;
            }
            throw new ArgumentException("Could not determine property name.", "propertyNameLambda");
        }
    }
}

   
    
    
    
    
    
    
    
  

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