I'm using the POCO t4 template generator that comes with VS 2012. I made few changes to include the Entity.Name, but I'm not able to figure out the primary key.
public string EntityClassOpening(EntityType entity)
{
return string.Format(
CultureInfo.InvariantCulture,
"{0} {1}partial class {2}{3}<{4},{5}>{6}",
Accessibility.ForType(entity),
_code.SpaceAfter(_code.AbstractOption(entity)),
_code.Escape(entity),
": EntityBase",
entity.Name,
entity.Name,
_code.StringBefore(" ", _typeMapper.GetTypeName(entity.BaseType)));
}
I don't find a way to find the primary key from the EntityType object hierarchy. It exposes properties but the property does not have anything to say it is a primary key.
Any help appreciated.
Just in case anyone is trying to do this while migrating RIA services stuff, I'm using the standard dbcontext template in VS2013 and have added two things to the entities template.
first you need:
using System.ComponentModel.DataAnnotations;
I put it just under the //---- block near the top.
Then I modified the bit of code that looks like this. Just search for the first name. My change is ef.IsKey... and adding the Key() attribute.
var simpleProperties = typeMapper.GetSimpleProperties(entity);
if (simpleProperties.Any())
{
foreach (var edmProperty in simpleProperties)
{
#>
<#if (ef.IsKey(edmProperty))
{#> [Key()]
<#}#>
<#=codeStringGenerator.Property(edmProperty)#>
<#
}
}
Use EntityType.KeyMembers property to get properties the primary key consists of.
I added this to the TypeMapper section, delighted with the results:
public IEnumerable<EdmProperty> GetPrimaryKeyProperties(EntityType type)
{
return type.KeyMembers.Select(s => (EdmProperty)s);
}
Related
Using Orchard CMS, I am dealing with a record and a part proxy, but cannot figure out how to save it into the DB. In fact, I confess I don't even know how to get the items I'm trying to save into this paradigm. I was originally using enum's for choices:
MyEmum.cs:
public enum Choices { Choice1, Choice2, Choice3, Choice4 }
MyRecord.cs:
public virtual string MyProperty { get; set; }
MyPart.cs:
public IEnumerable<string> MyProperty
{
get
{
if (String.IsNullOrWhiteSpace(Record.MyProperty)) return new string[] { };
return Record
.MyProperty
.Split(new[] { '.' }, StringSplitOptions.RemoveEmptyEntries)
.Select(r => r.Trim())
.Where(r => !String.IsNullOrEmpty(r));
}
set { Record.MyProperty = value == null ? null : String.Join(",", value); }
}
Now, in my service class, I tried something like:
public MyPart Create(MyPartRecord record)
{
MyPart part = Services.ContentManager.Create<MyPart>("My");
...
part.MyProperty = record.MyProperty; //getting error here
...
return part;
}
However, I am getting the following error: Cannot implicitly convert 'string' to System.Collections.Generic.IEnumerable<string>'
Essentially, I am trying to save choices from a checkboxlist (one or more selections) as a comma-separated list in the DB.
And this doesn't even get me over the problem of how do I use the enum. Any thoughts?
For some background:
I understand that the appropriate way to handle this relationship would be to create a separate table and use IList<MyEnum>. However, this is a simple list that I do not intend to manipulate with edits (in fact, no driver is used in this scenario as I handle this on the front-end with a controller and routes). I am just capturing data and redisplaying it in the Admin view for statistical/historical purposes. I may even consider getting rid of the Part (considering the following post: Bertrand's Blog Post.
It should be:
part.MyProperty = new[] {"foo", "bar"};
for example. The part's setter will store the value on the record's property as a comma-separated string, which will get persisted into the DB.
If you want to use enum values, you should use the Parse and ToString APIs that .NET provide on Enum.
I'm running into an issue with Entity Framework code-first in MVC3. I'm hitting this exception:
An object with the same key already exists in the ObjectStateManager.
The ObjectStateManager cannot track multiple objects with the same
key.
This is addressed many times on SO, but I'm having trouble utilizing any of the suggested solutions in my situation.
Here is a code sample:
FestORM.SaleMethod method = new FestORM.SaleMethod
{
Id = 2,
Name = "Test Sale Method"
};
FestContext context = new FestContext();
//everything works without this line:
string thisQueryWillMessThingsUp =
context.SaleMethods.Where(m => m.Id == 2).Single().Name;
context.Entry(method).State = System.Data.EntityState.Modified;
context.SaveChanges();
EDITED to clarify: I am attempting to update an object that already exists in the database.
Everything works fine without the query noted in the code. In my application, my controller is instantiating the context, and that same context is passed to several repositories that are used by the controller--so I am not able to simply use a different context for the initial query operation. I've tried to remove the entity from being tracked in the ObjectStateManager, but I can't seem to get anywhere with that either. I'm trying to figure out a solution that will work for both conditions: sometimes I will be updating an object that is tracked by the ObjectStateManager, and sometimes it will happen to have not been tracked yet.
FWIW, my real repository functions look like this, just like the code above:
public void Update(T entity)
{
//works ONLY when entity is not tracked by ObjectStateManager
_context.Entry(entity).State = System.Data.EntityState.Modified;
}
public void SaveChanges()
{
_context.SaveChanges();
}
Any ideas? I've been fighting this for too long...
The problem is that this query
string thisQueryWillMessThingsUp =
context.SaleMethods.Where(m => m.Id == 2).Single().Name;
brings one instance of the SaleMethod entity into the context and then this code
context.Entry(method).State = System.Data.EntityState.Modified;
attaches a different instance to the context. Both instances have the same primary key, so EF thinks that you are trying to attach two different entities with the same key to the context. It doesn't know that they are both supposed to be the same entity.
If for some reason you just need to query for the name, but don't want to actually bring the full entity into the context, then you can do this:
string thisQueryWillMessThingsUp =
context.SaleMethods.Where(m => m.Id == 2).AsNoTracking().Single().Name;
If what you are tying to do is update an existing entity and you have values for all mapped properties of that entity, then the simplest thing to do is to not run the query and just use:
context.Entry(method).State = System.Data.EntityState.Modified;
If you don't want to update all properties, possibly because you don't have values for all properties, then querying for the entity and setting properties on it before calling SaveChanges is an acceptable approach. There are several ways to do this depending on your exact requirements. One way is to use the Property method, something like so:
var salesMethod = context.SaleMethods.Find(2); // Basically equivalent to your query
context.Entry(salesMethod).Property(e => e.Name).CurrentValue = newName;
context.Entry(salesMethod).Property(e => e.SomeOtherProp).CurrentValue = newOtherValue;
context.SaveChanges();
These blog posts contain some additional information that might be helpful:
http://blogs.msdn.com/b/adonet/archive/2011/01/29/using-dbcontext-in-ef-feature-ctp5-part-4-add-attach-and-entity-states.aspx
http://blogs.msdn.com/b/adonet/archive/2011/01/30/using-dbcontext-in-ef-feature-ctp5-part-5-working-with-property-values.aspx
The obvious answer would be that your not actually saving the method object to the database before you call:
//everything works without this line:
string thisQueryWillMessThingsUp = context.SaleMethods.Where(m => m.Id == 2).Single().Name;
However, I think perhaps this is just a bit a code you left out.
What if you make your entities inherit from an abstract class ie.
public abstract class BaseClass
{
public int Id { get; set; }
}
Then update your Repository to
public class Repository<T> where T : BaseClass
{
.....
public void Update(T entity)
{
_context.Entry(entity).State = entity.Id == 0 ? System.Data.EntityState.Added : System.Data.EntityState.Modified;
}
}
Also you might want to not set the ID of your SaleMethod and let it be generated by the database. Problem could also be because SaleMethod Object in the database has Id of 2 and then you try to add another SaleMethod object with Id 2.
The error you see stems from trying to add another SaleMethod object with ID of 2 to the ObjectStateManager.
I've only been using fluent nhibernate a few days and its been going fine until trying to deal with guid values and Oracle. I have read a good few posts on the subject but none that help me solve the problem I am seeing.
I am using Oracle 10g express edition.
I have a simple test table in oracle
CREATE TABLE test (Field RAW(16));
I have a simple class and interface for mapping to the table
public class Test : ITest
{
public virtual Guid Field { get; set; }
}
public interface ITest
{
Guid Field { get; set; }
}
Class map is simple
public class TestMap : ClassMap<Test>
{
public TestMap()
{
Id(x => x.Field);
}
}
I start trying to insert a simple easily recognised guid value
00112233445566778899AABBCCDDEEFF
Heres the code
var test = new Test {Field = new Guid("00112233445566778899AABBCCDDEEFF")};
// test.Field == 00112233445566778899AABBCCDDEEFF here.
session.Save(test);
// after save guid is changed, test.Field == 09a3f4eefebc4cdb8c239f5300edfd82
// this value is different for each run so I pressume nhibernate is assigning
// a value internally.
transaction.Commit();
IQuery query = session.CreateQuery("from Test");
// or
// IQuery query = session.CreateSQLQuery("select * from Test").AddEntity(typeof(Test));
var t in query.List<Test>().Single();
// t.Field == 8ef8a3b10e704e4dae5d9f5300e77098
// this value never changes between runs.
The value actually stored in the database differs each time also, for the run above it was
EEF4A309BCFEDB4C8C239F5300EDFD82
Truly confused....
Any help much appreciated.
EDIT: I always delete data from the table before each test run. Also using ADO directly works no problem.
EDIT: OK, my first problem was that even though I thought I was dropping the data from the table via SQL command line for oracle when I viewed the table via oracle UI it still had data and the first guid was as I should have expected 8ef8a3b10e704e4dae5d9f5300e77098.
Fnhibernate still appears to be altering the guid value on save. it alters it to the value it stores in the database but I'm still not sure why it is doing this or how\if I can control it.
If you intend on assigning the id yourself you will need to use a different id generator than the default which is Guid.comb. You should be using assigned instead. So your mapping would look something like this:
Id(x => x.Field).GeneratedBy.Assigned();
You can read more about id generators in the nhibernate documentation here:
http://www.nhforge.org/doc/nh/en/index.html#mapping-declaration-id-generator
I have two tables in my database connected by foreign keys: Page (PageId, other data) and PageTag (PageId, Tag). I've used LINQ to generate classes for these tables, with the page as the parent and the Tag as the child collection (one to many relationship). Is there any way to mark PageTag records for deletion from the database from within the Page class?
Quick Clearification:
I want the child objects to be deleted when the parent DataContext calls SubmitChanges(), not before. I want TagString to behave exactly like any of the other properties of the Page object.
I would like to enable code like the following:
Page page = mDataContext.Pages.Where(page => page.pageId = 1);
page.TagString = "new set of tags";
//Changes have not been written to the database at this point.
mDataContext.SubmitChanges();
//All changes should now be saved to the database.
Here is my situation in detail:
In order to make working with the collection of tags easier, I've added a property to the Page object that treats the Tag collection as a string:
public string TagString {
get {
StringBuilder output = new StringBuilder();
foreach (PageTag tag in PageTags) {
output.Append(tag.Tag + " ");
}
if (output.Length > 0) {
output.Remove(output.Length - 1, 1);
}
return output.ToString();
}
set {
string[] tags = value.Split(' ');
PageTags.Clear();
foreach (string tag in tags) {
PageTag pageTag = new PageTag();
pageTag.Tag = tag;
PageTags.Add(pageTag);
}
}
}
Basically, the idea is that when a string of tags is sent to this property, the current tags of the object are deleted and a new set is generated in their place.
The problem I'm encountering is that this line:
PageTags.Clear();
Doesn't actually delete the old tags from the database when changes are submitted.
Looking around, the "proper" way to delete things seems to be to call the DeleteOnSubmit method of the data context class. But I don't appear to have access to the DataContext class from within the Page class.
Does anyone know of a way to mark the child elements for deletion from the database from within the Page class?
After some more research, I believe I've managed to find a solution. Marking an object for deletion when it's removed from a collection is controlled by the DeleteOnNull parameter of the Association attribute.
This parameter is set to true when the relationship between two tables is marked with OnDelete Cascade.
Unfortunately, there is no way to set this attribute from within the designer, and no way to set it from within the partial class in the *DataContext.cs file. The only way to set it without enabling cascading deletes is to manually edit the *DataContext.designer.cs file.
In my case, this meant finding the Page association, and adding the DeleteOnNull property:
[Association(Name="Page_PageTag", Storage="_Page", ThisKey="PageId", OtherKey="iPageId", IsForeignKey=true)]
public Page Page
{
...
}
And adding the DeleteOnNull attribute:
[Association(Name="Page_PageTag", Storage="_Page", ThisKey="PageId", OtherKey="iPageId", IsForeignKey=true, DeleteOnNull = true)]
public Page Page
{
...
}
Note that the attribute needed to be added to the Page property of the PageTag class, not the other way around.
See also:
Beth Massi -- LINQ to SQL and One-To-Many Relationships
Dave Brace -- LINQ to SQL: DeleteOnNull
Sorry, my bad. That won't work.
It really looks like you need to be doing this in your repository, rather than in your Page class. There, you have access to your original data context.
There is a way to "attach" the original data context, but by the time you do that, it has become quite the code smell.
Do you have a relationship, in your Linq to SQL entity diagram, linking the Page and PageTags tables? If you don't, that is why you can't see the PageTags class from the Page class.
If the foreign key in the PageTags database table is set to Allow Nulls, Linq to SQL will not create the link when you drag the tables into the designer, even if you created a relationship on the SQL Server.
This is one of those areas where OR mapping can get kind of hairy. Providing this TagString property makes things a bit more convenient, but in the long run it obfuscates what is really happening when someone utilizes the TagString property. By hiding the fact that your performing data modification, someone can very easily come along and set the TagString without using your Page entity within the scope of a DataContext, which could lead to some difficult to find bugs.
A better solution would be to add a Tags property on the Page class with the L2S model designer, and require that the PageTags be edited directly on the Tags property, within the scope of a DataContext. Make the TagString property read only, so it can be genreated (and still provide some convenience), but eliminate the confusion and difficulty around setting that property. This kind of change clarifies intent, and makes it obvious what is happening and what is required by consumers of the Page object to make it happen.
Since Tags is a property of your Page object, as long as it is attached to a DataContext, any changes to that collection will properly trigger deletions or insertions in the database in response to Remove or Add calls.
Aaron,
Apparently you have to loop thru your PageTag records, calling DeleteOnSubmit for each one. Linq to SQL should create an aggregate query to delete all of the records at once when you call SubmitChanges, so overhead should be minimal.
replace
PageTags.Clear();
with
foreach (PageTag tag in PageTags)
myDataContext.DeleteOnSubmit(tag);
Aaron:
Add a DataContext member to your PageTag partial class.
partial class PageTag
{
DataClassesDataContext myDataContext = new DataClassesDataContext();
public string TagString {
..etc.
Larger code sample posted at Robert Harvey's request:
DataContext.cs file:
namespace MyProject.Library.Model
{
using Tome.Library.Parsing;
using System.Text;
partial class Page
{
//Part of Robert Harvey's proposed solution.
MyDataContext mDataContext = new TomeDataContext();
public string TagString {
get {
StringBuilder output = new StringBuilder();
foreach (PageTag tag in PageTags) {
output.Append(tag.Tag + " ");
}
if (output.Length > 0) {
output.Remove(output.Length - 1, 1);
}
return output.ToString();
}
set {
string[] tags = value.Split(' ');
//Original code, fails to mark for deletion.
//PageTags.Clear();
//Robert Harvey's suggestion, thorws exception "Cannot remove an entity that has not been attached."
foreach (PageTag tag in PageTags) {
mDataContext.PageTags.DeleteOnSubmit(tag);
}
foreach (string tag in tags) {
PageTag PageTag = new PageTag();
PageTag.Tag = tag;
PageTags.Add(PageTag);
}
}
}
private bool mIsNew;
public bool IsNew {
get {
return mIsNew;
}
}
partial void OnCreated() {
mIsNew = true;
}
partial void OnLoaded() {
mIsNew = false;
}
}
}
Repository Methods:
public void Save() {
mDataContext.SubmitChanges();
}
public Page GetPage(string pageName) {
Page page =
(from p in mDataContext.Pages
where p.FileName == pageName
select p).SingleOrDefault();
return page;
}
Usage:
[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Edit(string pageName, FormCollection formValues) {
Page updatedPage = mRepository.GetPage(pageName);
//TagString is a Form value, and is set via UpdateModel.
UpdateModel(updatedPage, formValues.ToValueProvider());
updatedPage.FileName = pageName;
//At this point NO changes should have been written to the database.
mRepository.Save();
//All changes should NOW be saved to the database.
return RedirectToAction("Index", "Pages", new { PageName = pageName });
}
I am looking to get a list of the column names returned from a Model. Anyone know how this would be done, any help would be greatly appreciated.
Example Code:
var project = db.Projects.Single(p => p.ProjectID.Equals(Id));
This code would return the Projects object, how would I get a list of all the column names in this Model.
Thanks
This would be nice to have as an extension method:
public static class LinqExtensions
{
public static ReadOnlyCollection<MetaDataMember> ColumnNames<TEntity> (this DataContext source)
{
return source.Mapping.MappingSource.GetModel (typeof (DataContext)).GetMetaType (typeof (TEntity)).DataMembers;
}
}
example:
var columnNames = myDataContext.ColumnNames<Orders> ();
Thanks guys, you got me started on the right track. I found my solution with the following code. I can then iterate through the DataMembers and pull out their individual properties such as name, type, etc.
var db = new GMPDataContext();
var columnNames = db.Mapping.MappingSource
.GetModel(typeof(GMPDataContext))
.GetMetaType(typeof(Project))
.DataMembers;
Your Projects wrapper will have a set of properties each with a [Column] attribute. So just use reflection to enumerate the properties with that attribute.
Using Todd Smiths(+1) solution you get all properties (included entity sets, etc).
To filter out all non-column properties this will do the trick:
var columnNames = db.ColumnNames<Orders>().Where(n => n.Member.GetCustomAttributes(typeof(System.Data.Linq.Mapping.ColumnAttribute), false).FirstOrDefault() != null).Select(n => n.Name);
I am sorry, I don't have working experience with LINQ.
This is purely based on looking at MSDN.
DataContext has a Mapping property, which returns an instance of MetaModel.
MetaModel has GetMetaType, which takes a Type. In your case it could be typeof(Project).
GetMetaType returns a MetaType which has the GetDataMember method, which takes a MemberInfo parameter. You will have to use reflection on your Projects object to get the MemberInfo object.
The MetaDataMember instance returned by GetDataMember should have all the things, you need.
I hope I am somewhat in right direction (purely looking at MSDN & traversing)
Your columns should be mapped as properties on your Project model. I'm not sure if you can get the underlying database structure when using LINQ to SQL. The entire point of LINQ to SQL is to abstract the database away.
Here an another way:
public string[] GetColumnNames()
{
var propnames = GetPropertyNames(_context.Users);
return propnames.ToArray();
}
static IEnumerable<string> GetPropertyNames<T>(IEnumerable<T> lst)
{
foreach (var pi in typeof(T).GetProperties())
{
yield return pi.Name;
}
}