I am using CastleProject ActiveRecord.
I have the following property in my class:
[HasMany(typeof(Order), Table = "Orders", ColumnKey = "OrderId")]
internal IList<Order> Orders
{
get;
set;
}
In case Orders table does not contain any orders, Orders property is null. Can I somehow point ActiveRecord that it should create empty list instead of returning null, without giving up autoproperty?
Not exactly what you want, but couldn't you instantiate an empty list in the constructor:
public MyClass()
{
Orders = new List<Order>();
}
Related
I need to return from a query a list of students where each students has assignments.
class Student {
public string Name{ get; set; }
public IEnumerable<Assignment> Assignments{ get; set; }
}
class Assignment {
public string Title { get; set; }
}
so tried to create two queries and then use include/includemany but i get other errors (The given key 'Id' was not present in the dictionary)
var students = db.Query('Student')
.Select(...)
.Where()
var assignments= db.Query('Assignment')
.Select(...)
.Where()
var result = students.IncludeMany('Assignments', assignments).Get()
but this does not work. How can you properly create complex/nested objects with SQLKata?
I asume your example is complete, but you should add the primairy and foreign key properties on the queries. (They are not in your classes so I added them based on conventions sql kata uses)
var students = db.Query("Student")
.Select("Id", "Name");
var assignments = db.Query("Assignment")
.Select("StudentId", "Title");
var result = students
.IncludeMany("Assignments", assignments)
.Get();
If they are not specified as an argument to the IncludeMany method, SqlKata will use the "Id" field as primary key and the "StudentId" field as the foreign key in the relationship. You can add these as extra arguments to the IncludeMany method.
var result = students
.IncludeMany("Assignments", assignments, "StudentId", "Id")
.Get();
Please note that at this moment SqlKata doesn't seem to support this on the generic method Get<> GetAsync<>.
Below is my code for entity and a function where I need to map entity TblEmployee from a key value pair.
In foreach loop I am getting values based on keys, what should be the best approach to do it?
public class TblEmployee
{
public int EmployeeId { get; set; }
public string Name { get; set; }
}
public int Create()
{
tblEmployee employee = new tblEmployee();
using (var ctx = new theparkeee_testEntities())
{
foreach (string key in HttpContext.Current.Request.Form.AllKeys)
{
string value = HttpContext.Current.Request.Form[key];
//how to map value from key value pair to entity employee.
}
}
}
You can use System.Reflection to get the Properties of an object by their name with Type.GetProperty(string name). After you got the PropertyInfo, you can use SetValue to assign a value to it.
foreach (string key in HttpContext.Current.Request.Form.AllKeys) {
// note that "value" is a reserved word, do not use it as variable name
string val = HttpContext.Current.Request.Form[key];
var propertyInfo = typeof(TblEmployee).GetProperty(key); // can maybe be moved outside of the loop
if (propertyInfo != null) {
propertyInfo.SetValue(employee, val);
}
}
This will work for string properties. If the property is of another type, you have to find the correct type (again, using reflection) and cast the string value before assigning it.
Note that this is not the correct approach to store data in MVC. You should not work with the Request.Form directly, instead your POST action should accept a ViewModel that can be mapped (e.g. using Automapper) to the DB entity. I.e. let the ASP ModelBinder do its work, instead of reinventing the wheel!
[HttpPost]
public ActionResult Submit(MyViewModel postData) {
var employee = Mapper.Map<TblEmployee>(postData);
_ctx.Employees.Add(employee);
_ctx.SaveChanges();
return new HttpStatusCodeResult((int)HttpStatusCode.OK);
}
I'm using dapper 1.50.2 with MySQL and running into a problem trying to map a left outer join child object to its parent. If I split on a column alias that doesn't actually exist in the child object, Dapper always creates a child object with default properties, even when there is nothing in the left join.
I created a simple example to demonstrate this:
public class ParentRecord
{
public string MemberID { get; set; }
public ChildRecord Child { get; set; }
}
public class ChildRecord
{
//public string Split { get; set; }
public string SomeField { get; set; }
}
using (MySqlConnection connection = new MySqlConnection(connectionString))
{
ParentRecord result = connection.Query<ParentRecord, ChildRecord, ParentRecord>(
#"SELECT 'FakeID' AS MemberID, NULL AS Split, NULL AS SomeField",
(mt, crt) =>
{
mt.Child = crt;
return mt;
},
splitOn: "Split").Single();
}
I would expect this to result a ParentRecord with the Child property set to null, but the Child property is set to a ChildRecord with all default fields.
If I uncomment the Split property in ChildRecord, or if I split on SomeField, this works as I'd expect.
Are there any good workarounds for this?
In the actual query I'm dealing with, there are multiple primary key and foreign key fields with the same names and I'd rather not change the property names in the POCOs to be unique. I'd prefer to be able to use column aliases that are just there to split on. I know this isn't normally how Dapper is set to up to work.
Any help would be appreciated, thanks.
This happen because the object Child initialize for default when you attribute the ctr param. Then the solution that I did implement was:
ParentRecord result = connection.Query<ParentRecord, ChildRecord, ParentRecord>(
#"SELECT 'FakeID' AS MemberID, NULL AS Split, NULL AS SomeField",
(mt, crt) =>
{
if (crt.SomeField != null){ mt.Child = crt; }
return mt;
},
splitOn: "Split").Single();
I'd like to know how can I make Entity Framework update an object instead of always inserting a new one for each new main object.
For example:
I have these objects:
Main Object:
public class ExtraArticleAttributes
{
[Key]
public int extraarticleattributes_id { get; set; }
virtual public WorldData world_data { get; set; }
}
Its dependencie:
public class WorldData
{
[Key]
public int worlddata_id { get; set; }
public string country { get; set; }
So, how can I make Entity Framework when inserting a new ExtraArticleAttributes verify if already exists a WorldData object and only update it?
I've been reading some articles about it and I notice that Entity Framework identify an existing object in DB with a HASH code, so when I get it from an API, and try to insert It in the DB, even though the object has the same data, the Entity Framework doesn't recognize like an existed object in DB. Does exist a way of make It, without spending request to the DB to verify if the object exists, if true get It.
Set the entity state to Modified:
using System.Data.Entity;
// Assuming that there is already an existing WorldData record in the database with id 1 and country 'foo', and you want to change the country to 'bar'
using (var context = new MyContext())
{
var extraArticleAttributes = new ExtraArticleAttributes
{
world_data = new WorldData
{
worlddata_id = 1,
country = "bar"
}
};
db.ExtraArticleAttributes.Add(extraArticleAttributes);
db.Entry<WorldData>(extraArticleAttributes.world_data).State = EntityState.Modified;
db.SaveChanges();
// world data 1 country is now 'bar'
}
I have a autocompletebox that is used to select a destination for a car booking program. For the itemssource of the autocomplete box I am trying to set it to all the previous destinations entered. The problem is that I can't work out how to return a single column 'Destination' of distinct destination values from my Booking class, e.g.
var query = from bk in ObjectContext.Bookings select new DestinationDTO { Destination = bk.Destination };
return query.Distinct();
. I have tried creating a shared DestinationDTO class to return just the single column but can't work out how to get this to inherit from Entity!!
Any ideas?
You need to have a property with a [Key] attribute in your DestinationDTO class. Then RIA services will be able to generate a corresponding class on the client side.
public class DestinationDTO
{
[Key]
public Guid Id { get; set; }
public string Destination { get; set; }
}
Then just do this:
var query = from bk in ObjectContext.Bookings
select new DestinationDTO { Destination = bk.Destination, Id = Guid.NewGuid() };
return query.Distinct();