tnb.server/common/Tnb.Common/Extension/LambdaExpressionExtensions.cs

using System.Linq.Expressions;

namespace JNPF.Common.Extension
{
    public static class LambdaExpressionExtensions
    {
        public static void PropertySetValue<T>(this T instance, string propertyName, string value)
        {
            if (!PropertySet<T>.ValueFactories.TryGetValue(propertyName, out Action<object, object> setAction))
            {
                setAction = PropertySet<T>.CreateSetPropertyValueAction(propertyName);
                PropertySet<T>.ValueFactories.Add(propertyName, setAction);
            }
            setAction(instance, value);
        }

        public static void PropertySetValue<T>(this T instance, string propertyName, object value)
        {
            if (!PropertySet<T>.ValueFactories2.TryGetValue(propertyName, out Action<T, object> setAction))
            {
                setAction = PropertySet<T>.CreateSetPropertyValueAction2(propertyName);
                PropertySet<T>.ValueFactories2.Add(propertyName, setAction);
            }
            setAction(instance, value);
        }

        /// <summary>
        /// Lambda表达式拼接
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="first"></param>
        /// <param name="second"></param>
        /// <param name="merge"></param>
        /// <returns></returns>
        public static Expression<Func<T1, T2, T3, bool>> Compose<T1, T2, T3>(this Expression<Func<T1, T2, T3, bool>> first, Expression<Func<T1, T2, T3, bool>> second,
            Func<Expression, Expression, Expression> merge)
        {
            // build parameter map (from parameters of second to parameters of first)
            var map = first.Parameters.Select((f, i) => new { f, s = second.Parameters[i] }).ToDictionary(p => p.s, p => p.f);
            // replace parameters in the second lambda expression with parameters from the first
            var secondBody = ParameterRebinder.ReplaceParameters(map, second.Body);
            // apply composition of lambda expression bodies to parameters from the first expression 
            return Expression.Lambda<Func<T1, T2, T3, bool>>(merge(first.Body, secondBody), first.Parameters);
        }
        /// <summary>
        /// and扩展
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="first"></param>
        /// <param name="second"></param>
        /// <returns></returns>
        public static Expression<Func<T1,T2,T3, bool>> And<T1, T2, T3>(this Expression<Func<T1, T2, T3, bool>> first, Expression<Func<T1, T2, T3, bool>> second)
        {
            if (first.IsNull())
            {
                first = second;
                return first;
            }

            return first.Compose(second, Expression.And);
        }
    }


    public class ParameterRebinder : ExpressionVisitor
    {
        private readonly Dictionary<ParameterExpression, ParameterExpression> map;
        /// <summary>
        /// 
        /// </summary>
        /// <param name="map"></param>
        public ParameterRebinder(Dictionary<ParameterExpression, ParameterExpression> map)
        {
            this.map = map ?? new Dictionary<ParameterExpression, ParameterExpression>();
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="map"></param>
        /// <param name="exp"></param>
        /// <returns></returns>
        public static Expression ReplaceParameters(Dictionary<ParameterExpression, ParameterExpression> map, Expression exp)
        {
            return new ParameterRebinder(map).Visit(exp);
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="p"></param>
        /// <returns></returns>
        protected override Expression VisitParameter(ParameterExpression p)
        {
            ParameterExpression replacement;
            if (map.TryGetValue(p, out replacement))
            {
                p = replacement;
            }
            return base.VisitParameter(p);
        }
    }
    public class PropertySet<T>
    {
        public static Dictionary<string, Action<object, object>> ValueFactories = new Dictionary<string, Action<object, object>>(StringComparer.OrdinalIgnoreCase);
        public static Dictionary<string, Action<T, object>> ValueFactories2 = new Dictionary<string, Action<T, object>>(StringComparer.OrdinalIgnoreCase);

        public static Action<object, object> CreateSetPropertyValueAction(string propertyName)
        {
            var property = typeof(T).GetProperty(propertyName);
            var target = Expression.Parameter(typeof(object));
            var propertyValue = Expression.Parameter(typeof(object));
            var castTarget = Expression.Convert(target, typeof(T));
            var castPropertyValue = Expression.Convert(propertyValue, property!.PropertyType);
            var setPropertyValue = Expression.Call(castTarget, property.GetSetMethod()!, castPropertyValue);
            return Expression.Lambda<Action<object, object>>(setPropertyValue, target, propertyValue).Compile();
        }

        public static Action<T, object> CreateSetPropertyValueAction2(string propertyName)
        {
            var property = typeof(T).GetProperty(propertyName);
            var target = Expression.Parameter(typeof(T));
            var propExp = Expression.Property(target, propertyName);
            var propertyValue = Expression.Parameter(typeof(object));
            var castPropertyValue = Expression.Convert(propertyValue, property!.PropertyType);
            var assignExp = Expression.Assign(propExp, castPropertyValue);

            return Expression.Lambda<Action<T, object>>(assignExp, new[] { target, propertyValue }).Compile();
        }

    }
}