var filter = new Filter<Person>();
filter.By("Id", Operation.Between, 2, 4,  Connector.And);
filter.By("Contacts[Value]", Operation.EndsWith, "@email.com", default(string), Connector.And);
filter.By("Birth.Country", Operation.IsNotNull, default(string), default(string),  Connector.Or);
filter.By("Name", Operation.Contains, " John");
var people = People.Where(filter);

//or like this...

var filter = new Filter<Person>();
filter.By("Id", Operation.Between, 2, 4)
      .And.By("Birth.Country", Operation.IsNotNull)
      .And.By("Contacts[Value]", Operation.EndsWith, "@email.com")
      .Or.By("Name", Operation.Contains, " John ");
var people = People.Where(filter);

People.Where(p => (p.Id >= 2 && p.Id <= 4)
             && (p.Birth != null && p.Birth.Country != null)
             && (p.Contacts != null && p.Contacts.Any(c => c.Value.Trim().ToLower().EndsWith("@email.com")))
             || (p.Name != null  && p.Name.Trim().ToLower().Contains("john")));

        /// <summary>
        /// Insert values from an object into a string pattern. To specify the object's property you have to use the '{propertyName}'.
        /// </summary>
        /// <remarks>
        /// This method is a replacement to String.Format, but it has two differences:
        /// <list type="simple">
        /// <item>It reverese the order you call the functionality, instead of writing String.Format(pattern, args) you write pattern.FillByObject(args). This makes the code look cleaner.</item>
        /// <item>You supply the pattern with an object and specify insertion points by property names.</item>
        /// </list>
        /// <example>
        /// <![CDATA[
        /// "First name:{firstName}, Sur name:{Surname}".FillByObject(new {firstName = "Sam", lastName="Naseri"});
        /// ]]>
        /// </example>
        /// </remarks>
        /// <seealso cref="Fill"/>
        /// <typeparam name="T">Type of bindingValue.</typeparam>
        /// <param name="bindingPattern">The pattern to fill.</param>
        /// <param name="bindingValue">The object providing values to fill in the pattern.</param>
        /// <returns>The pattern filled with values.</returns>
        public static string FillByObject<T>(this string bindingPattern, T bindingValue)
        {
            var properties = GetProperties(typeof(T)).ToList();
            var values = properties.Select(property => property.GetValue(bindingValue, new object[] { })).ToList();
            var result = bindingPattern;
            for (int index = 0; index < properties.Count; index++)
            {
                var property = properties[index];
                var propPattern = "{" + property.Name + "}";
                var old = result;
                result = result.Replace(propPattern, values[index] != null ? values[index].ToString() : "");
            }
            return result;
        }

private static IEnumerable<PropertyInfo> GetProperties(Type t)
{
    return t.GetProperties(BindingFlags.Public | BindingFlags.Instance);
}

/// <summary>
/// A simple replacement for String.Format which only makes the codes look nicer.
/// </summary>
/// <param name="pattern">The source string that you want to replace insertion points on it.</param>
/// <param name="args">Values to be replaced in the pattern.</param>
/// <returns></returns>
public static string Fill(this string pattern, params object[] args)
{
    return string.Format(pattern, args);
}

Views\UploadFileExtensions\Index.cshtml(25,135): 
error CS1061: 'UserFileViewModel' does not contain a definition for 'UserFile' 
and no extension method 'UserFile' accepting a first argument of type 'UserFileViewModel' could be found 
(are you missing a using directive or an assembly reference?)