实体框架 Include() 强类型

Question

Is there a way to make this strongly typed using the System.Data.Entity.Include method? In the method below Escalation is a ICollection<>.

public IEnumerable<EscalationType> GetAllTypes() {
  Database.Configuration.LazyLoadingEnabled = false;
  return Database.EscalationTypes
    .Include("Escalation")
    .Include("Escalation.Primary")
    .Include("Escalation.Backup")
    .Include("Escalation.Primary.ContactInformation")
    .Include("Escalation.Backup.ContactInformation").ToList();
}

Answer 1

This is already available in Entity Framework 4.1.

See here for a reference for how to use the include feature, it also shows how to include multiple levels: http://msdn.microsoft.com/en-us/library/gg671236(VS.103).aspx

The strongly typed Include() method is an extension method so you have to remember to declare the using System.Data.Entity; statement.

Answer 2

Credit goes to Joe Ferner :

public static class ObjectQueryExtensionMethods {
  public static ObjectQuery<T> Include<T>(this ObjectQuery<T> query, Expression<Func<T, object>> exp) {
    Expression body = exp.Body;
    MemberExpression memberExpression = (MemberExpression)exp.Body;
    string path = GetIncludePath(memberExpression);
    return query.Include(path);
  }

  private static string GetIncludePath(MemberExpression memberExpression) {
    string path = "";
    if (memberExpression.Expression is MemberExpression) {
      path = GetIncludePath((MemberExpression)memberExpression.Expression) + ".";
    }
    PropertyInfo propertyInfo = (PropertyInfo)memberExpression.Member;
    return path + propertyInfo.Name;
  }
}

ctx.Users.Include(u => u.Order.Item)