表达式目录树拼接两个表达式

 public static Expression<Func<T, bool>> CreateWhere<T>(string columnName, Type columnType, object value,Expression<Func<T, bool>> expression=null)
        {
            if (typeof(T).GetProperties().Any(p=>p.Name==columnName))
            {
                var parameter = Expression.Parameter(typeof(T), "w");
                var lambdaBody = Expression.Equal(
                    Expression.PropertyOrField(parameter, columnName),
                    Expression.Constant(value, columnType)
                    );
                if (expression != null)
                {
                    var data = Expression.AndAlso(lambdaBody, expression.Body);
                    return Expression.Lambda<Func<T, bool>>(data, parameter);
                }
                return Expression.Lambda<Func<T, bool>>(lambdaBody, parameter);
            }
            return null;
        }