I have the following code -
public void LoadAllContacts()
{
var db = new ContextDB();
var contacts = db.LocalContacts.ToList();
grdItems.DataSource = contacts.OrderBy(x => x.Areas.OrderBy(y => y.Name));
grdItems.DataBind();
}
I'm trying to sort the list of the contacts according to the area name that is contained within each contact. When I tried the above, I get "At least one object must implement IComparable.". Is there an easy way instead of writing a custom IComparer?
Thanks!
try this:
public void LoadAllContacts()
{
var db = new ContextDB();
var contacts = db.LocalContacts.ToList();
grdItems.DataSource = contacts.OrderBy(x => x.Areas.OrderBy(y => y.Name).First().Name);
grdItems.DataBind();
}
this will order the contacts by the first area name, after ordering the areas by name.
Hope this helps :)
Edit: fixed error in code. (.First().Name)
I was in a discussion with #AbdouMoumen but in the end I thought I'd provide my own answer :-)
His answer works, but there two performance issues in this code (both in the answer as in the original question).
First, the code loads ALL contacts in the db. This may or may not be a problem, but in general I would recommend NOT to do this. Many modern controls support paging/filtering out of the box, so you'd be better off supplying an not-yet-evaluated IQueryable<T> instead of List<T>. If however you need everything in memory, you should delay the ToList to the last possible moment.
Second, in AbdouMoumen's answer, there is a so-called 'SELECT N+1' problem. Entity Framework will by default use lazy loading to fetch additional properties. I.e. the Areas property will not be fetched from the database until it's accessed. In this case this will happen in the controls 'for loop', while it's ordering the result set by name.
Open up SQL Server Profiler to see what I mean: you will see a SELECT statement for all the contacts, and an additional SELECT statement for each contact that fetches the Areas for that contact.
A much better solution would be the following:
public void LoadAllContacts()
{
using (var db = new ContextDB())
{
// note: no ToList() yet, just defining the query
var contactsQuery = db.LocalContacts
.OrderBy(x => x.Areas
.OrderBy(y => y.Name)
.First().Name);
// fetch all the contacts, correctly ordered in the DB
grdItems.DataSource = contactsQuery.ToList();
grdItems.DataBind();
}
}
Is it one to one relation (Contact->Area)?
if yeah then try the following :
public partial class Contact
{
public string AreaName
{
get
{
if (this.Area != null)
return this.Area.Name;
return string.Empty;
}
}
}
then
grdItems.DataSource = contacts.OrderBy(x => x.AreaName);
Related
I wrote a simple recursive function to climb up the tree of a table that has ID and PARENTID.
But when I do that I get this error
System.InvalidOperationException: 'The instance of entity type 'InternalOrg' cannot be tracked because another instance with the same key value for {'Id'} is already being tracked. When attaching existing entities, ensure that only one entity instance with a given key value is attached.
Is there another way to do this or maybe done in one LINQ expression ?
private InternalOrgDto GetInternalOrgDto(DepartmentChildDto dcDto)
{
if (dcDto.InternalOrgId != null)
{
InternalOrg io = _internalOrgRepo.Get(Convert.ToInt32(dcDto.InternalOrgId));
InternalOrgDto ioDto = new InternalOrgDto
{
Id = io.Id,
Abbreviation = io.Abbreviation,
Code = io.Code,
Description = io.Description
};
return ioDto;
}
else
{
//manually get parent department
Department parentDepartment = _departmentRepo.Get(Convert.ToInt32(dcDto.ParentDepartmentId));
DepartmentChildDto parentDepartmenDto = ObjectMapper.Map<DepartmentChildDto>(parentDepartment);
return GetInternalOrgDto(parentDepartmenDto);
}
}
Is there a way to get a top-level parent from a given child via Linq? Not that I am aware of. You can do it recursively similar to what you have done, though I would recommend simplifying the query to avoid loading entire entities until you get what you want. I'm guessing from your code that only top level parent departments would have an InternalOrg? Otherwise this method would recurse up the parents until it found one. This could be sped up a bit like:
private InternalOrgDto GetInternalOrgDto(DepartmentChildDto dcDto)
{
var internalOrgid = dcDto.InternalOrgId
?? FindInternalOrgid(dcDto.ParentDepartmentId)
?? throw new InternalOrgNotFoundException();
InternalOrgDto ioDto = _context.InternalOrganizations
.Where(x => x.InternalOrgId == internalOrgId.Value)
.Select(x => new InternalOrgDto
{
Id = x.Id,
Abbreviation = x.Abbreviation,
Code = x.Code,
Description = x.Description
}).Single();
return ioDto;
}
private int? FindInternalOrgid(int? departmentId)
{
if (!departmentId.HasValue)
return (int?) null;
var details = _context.Departments
.Where(x => x.DepartmentId == departmentId.Value)
.Select(x => new
{
x.InternalOrgId,
x.ParentDepartmentId
}).Single();
if (details.InternalOrgId.HasValue)
return details.InternalOrgId;
return findInternalOrgId(details.parentDepartmentId);
}
The key considerations here are to avoid repository methods that return entities or sets of entities, especially where you don't need everything about an entity. By leveraging the IQueryable provided by EF through Linq we can project down to just the data we need rather than returning every field. The database server can accommodate this better via indexing and help avoid things like locks. If you are using repositories to enforce low level domain rules or to enable unit testing then the repositories can expose IQueryable<TEntity> rather than IEnumerable<TEntity> or even TEntity to enable projection and other EF Linq goodness.
Another option to consider where I have hierarchal data where the relationships are important and I want to quickly find all related entities to a parent, or get to a specific level, one option is to store a breadcrumb with each record which is updated if that item is ever moved. The benefit is that these kinds of checks become very trivial to do, the risk is that anywhere/anything that can modify data relationships could leave the breadcrumb trail in an invalid state.
For example, if I have a Department ID 22 which belongs to Department 8 which belongs to Department 2 which is a top-level department, 22's breadcrumb trail would be: "2,8". If the breadcrumbs are empty we have a top-level entity. (and no parent Id) We can parse the breadcrumbs using a simple string.Split() operation. This avoids the recursive trips to the DB entirely. Though you may want a maintenance job running behind the scenes to periodically inspect recently modified data to ensure their breadcrumb trails are accurate and alerting you if any get broken. (Either by faulty code or such)
I am working on a MVC3 application with nhibernate and SQL server. Have written a normal method which is re-usable. Please find the below code and let me know a better way to handle it. I have observed to execute this piece of code it is taking a long time.
private void GetParentCompany(IEnumerable<Company> companiesList)
{
foreach (var company in companiesList)
{
long? dunsUltimateParent = company.DUNSUltimateParent;
Company ultimateParent = _companyService.GetCompanyByDUNS(Convert.ToInt64(dunsUltimateParent));
if (ultimateParent != null)
{
company.UltimateParentName = ultimateParent.CompanyName;
company.UltimateCompanyId = ultimateParent.CompanyId;
company.UltimateParentDuns = ultimateParent.DUNS;
}
}
}
Adding an index to your company.DUNS column might help. However consider to introduce a many-to-one relationship from company to (parent) company.
Place a UltimateParent property with type company in the company class. The fields UltimateParentName and UltimateParentDuns would then be redundant and you could simply get company.UltimateParent.Name for example. The mapping of UltimateParent can be done using 'References' in fluent-nhibernate.
References(x => x.UltimateParent);
I have a site I'm porting to MVC to clean up the code and simplify things. I use the asp membership and profile providers, but I'm wondering if I'm doing this correctly for my situtation. I'm pretty new to MVC, so I wan to get this right in the early stages.
Users are individuals and they are part of larger "institutions" that they either set up or pick at registration. In this case, the institution is a winery. I want the users to be able to view all wines from every winery, but only edit ones that belong to them.
What's the best way to do this? Right now I render the link to the edit field in my index view based on their instution ID and the producer ID. I feel like a data annotation might work better here, but I don't exactly how to implement that for a group of wines. Do I need multiple providers? I use roles to limit the editing, but right now an editor role could manually enter the path of another wine to edit it when that wine doesn't belong to them.
Any pointers here would be awesome. I know I can do it in the controller methods, but I'm looking for the 'right' way to do it. Thanks.
I'm running into the same issue at work right now, and the best proposed solution we have right now is implementing an "ownership" table. You won't be able to solve this using roles.
So basically you have an owner ID, owned object's ID, and the type of objects ID all held together. Lets take an edit request for example. We know that you can only edit the data person X owns, so we have a stored procedure that if a key combination exists in our ownership table where person.ID = owner ID, and item.ID = object ID, and item.TypeID = objectTypeID. If it exists, it goes along performing its edits, otherwise it returns an error.
You can use this scheme to return ownership lists, user validation, and a host of other issues you may come across. You probably won't need the ObjectTypeID if you only have one type's ownership being tracked. Hope this helps!
I figured this out by applying a custom AuthorizeAttribute to the edit, delete, and create actions.
Here is what I ended up doing:
public class ProducerEditAttribute : AuthorizeAttribute
{
private vfContext db = new vfContext();
public override void OnAuthorization(AuthorizationContext filterContext)
{
base.OnAuthorization(filterContext);
bool bAdmin = filterContext.HttpContext.User.IsInRole("admin");
bool bProdEdit = filterContext.HttpContext.User.IsInRole("producereditor");
bool bProd = filterContext.HttpContext.User.IsInRole("producer");
if (filterContext.HttpContext.User.Identity.IsAuthenticated)
{
if (bAdmin)
{
//authorized
}
if (bProdEdit || bProd)
{
//check for current wine belonging to the producer.
Producer currentProd = db.Producers.Find(Profile.GetProfile(filterContext.HttpContext.User.Identity.Name).InstitutionID);
Wine currentWine;
object WineID;
if (filterContext.RouteData.Values.TryGetValue("id", out WineID))
{
currentWine = db.Wines.Find(int.Parse(WineID.ToString()));
if (currentProd.Wines.Contains(currentWine) && bProdEdit)
{
//authorized
}
else if (bProd)
{
var result = new ViewResult();
result.ViewName = "Login.cshtml"; //this can be a property you don't have to hard code it
result.MasterName = "_Layout.cshtml"; //this can also be a property
result.ViewBag.Message = "You do not have permission for add/edit/delete funciontionality. Please request.";
filterContext.Result = result;
}
else
{
var result = new ViewResult();
result.ViewName = "Login.cshtml";
result.MasterName = "_Layout.cshtml";
filterContext.Result = result;
}
}
}
else
{
var result = new ViewResult();
result.ViewName = "Login.cshtml";
result.MasterName = "_Layout.cshtml";
}
}
}
}
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;
}
}