ADO.NET :: Entity Framework - How To Join Tables Without LINQ And With Only String
Sep 30, 2010
I have a question about Entity Framework. answer if you know answer on this. I have such query :
[Code]....
Particularly I want to join few tables in one query, but I can NOT use LINQ and can NOT use ObjectQuery with objects mapped to DB fields inside my query. Because each entity creates dynamically. So this is what i
can NOT use : [URL]
The question is can I use something like this instead of using objects?
[Code]....
The purpose is to use Join method of ObjectQuery with syntax as in Where method :[URL]
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Similar Messages:
Dec 10, 2010
I want to write a query in Entity Framework that has multiple joins. The only problem is the tables arn't related using their primary / foreign keys (its the Umbraco database), as such I can't use .Include and the Navigation properties.
Essentially the query I would like to run is this:
select t.*, n.* from cmsContentType t
inner join cmsContentTypeAllowedContentType a on t.nodeId = a.Id
inner join vicinity.DocumentTypeExtendedProperty x on x.UmbracoDocumentTypeId = t.pk
inner join umbracoNode n on n.id = t.nodeId
I have two EF entities mapped to cmsContentType and umbracoNode as such I would like them to be populated as if I was running the query like
var q = from p in cmsContentType.Include("umbracoNode")
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May 17, 2010
how to do this query in EF1:
[Code]....
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Jan 24, 2011
I need to make a category filter. For this purpose I have two tables "Ingredient" and "Category"
My Category Table looks like this:
[Code]....
And my ingredient table:
[Code]....
I want to join the two tables so when the KategoriID match it should then return all from that category.
[Code]....
[Code]....
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Sep 9, 2010
I was trying to find out how I can join more than 2 tables using the LINQ-to-SQL syntax. For instance, joining 2 tables in SQL:
SELECT * FROM Table1 AS T1 INNER JOIN Table2 AS T2 ON T1.Key=T2.Column1WHERE T2.Key='17';
can be expressed as:
var Result = from T1 in DbContext.Table1 join T2 in DbContext.Table2 on T1.Key equals T2.ForeignKey where T2.Key=17 select new { T1, T2 };
But how would I join 3 or more tables using LINQ? For example:
SELECT * FROM (Table1 AS T1 INNER JOIN Table2 AS T2 ON T1.Key=T2.Column1) INNER JOIN Table3 AS T3 ON T3.Key=T2.Column2 WHERE T2.Key='37';
I've been searching and experimenting and I cannot seem to find any informraiton on this. One example I found involves putting the result for the frist join into a temp object, and then performing the second join. I'm not sure performance-wise if that's the same as doing a 3-table join directly using a single SQL statement.
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Dec 9, 2010
I have T_articles to save the articles.
each article has authorCode , and categoryCode.
each article can be modified by the author several times.
and I save every modification in the T_articles in a difference row.
now I want to dislpay for each autor:
author name, article name , article category's name, last modified date
In SQL I should to it like that:
[Code]....
I try to write it in Linq so:
[Code]....
so I got error:
[Code]....
and again I got an error:
[Code]....
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Nov 9, 2010
Here's my DB structure:
I have three tables.
User, Details, Optional
User has fields: ID, FirstName, LastName
Details has fields: ID, MyDetails1, MyDetails2, User_ID
Optional has fields: ID, MyOptions1, MyOptions2, User_ID
There is a 1 to many relationship with User & Detail (User ID & Detail User_ID)
There is a 1 to many relationship with User & Optional (User ID & Optional User_ID)
With that said, one user can have many details and/or many optionals
Now I'm trying to build a linq query that will say:
"where user id = x, select FirstName, LastName, all MyDetails1 from every record where User_ID == x, all MyOptions1 from every record where User_ID == x"
After the merge I should have one string that lists the distict user & all of their many fields:
FirstName + LastName + (MyDetails1 + MyDetails1 + MyDetails1..etc) + (MyOptions1 + MyOptions1)
Anyone try this before?
I tried this with JOIN but this doesn't do the trick for what I'm looking for.
So if I had 3 MyDetails records associated with ID == 2, I would get three results like:
John Doe MyDetails_X
John Doe MyDetails_Y
John Doe MyDetails_Z
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Jan 8, 2011
The main problem is that I recieve the following message:
"base {System.SystemException} = {"Unable to create a constant value of type 'BokButik1.Models.Book-Author'. Only primitive types ('such as Int32, String, and Guid') are supported in this context."}"
based on this LinQ code:
[Code]....
How shall I solve this problem to get a class instance that contain with property title and Book-AuthorID?I also have tried making some dummy by using "allbooks" relation with Code Samples from the address
http://www.hookedonlinq.com/JoinOperator.ashx. Unfortunately, still same problem.
I also have taken account to Int32 due to entity framework http://msdn.microsoft.com/en-us/library/bb896317.aspx. Unfortunatley, still same problem.
Using database with 3 tables and one of them is a many to many relationship. This database is used in relation with entity framework
Book-Author
Book-Author (int)
BookID (int)[code]....
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Jan 22, 2010
I have two tables namely "CategoryMapping" and "PartnerCategory"...The partnercategory table has foreign key with categorymapping on CategoryID...
let us say categorymapping should be filed first then partnercategory should be filed based on the categories defined in categorymapping. For example my two tables have the following data:
[code]....
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Mar 4, 2011
I want to get data from Projects(which have CourseId) and related CourseName from Courses table.
I have written following code:
var projects = from n in db.Projects
join c in db.Courses on n.CourseId equals c.ID
orderby n.Name
select new { Project = n, Course = c };
return View(projects.ToList());
and I get error:
The model item passed into the dictionary is of type 'System.Collections.Generic.List1[<>f__AnonymousType22[ProjectManager.Models.Project,ProjectManager.Models.Course]]', but this dictionary requires a model item of type 'System.Collections.Generic.IEnumerable`1[ProjectManager.Models.Project]'.
What I need to do in Controller and in View to display this data?
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Nov 16, 2010
I'm having trouble doing a left outer join with multiple generic lists tables. I've been researching for hours and there isn't a whole lot out there on this subject and VB (at least what I found).
I have the following Linq query:
Dim DataForGridview = (From s In S1 _
Join c In C1 On c.ID Equals s.ID _
Join v In V1 On v.ID Equals s.ID _
Select New With { _
.dataFieldID = s.ID, _
.dataField1 = s.dataField1, _
.dataField2 = c.dataField2, _
.dataField3 = c.dataField3, _
.dataField4 = c.dataField4, _
.dataField5 = v.dataField5 _
}).ToList()
S1 has a count of 30. V1 has a count of 20. C1 has a count of 10. This query joins the three but ends up with a count of only 10 based on the datakey ID and, of course, only shows those 10 in the gridview.
I would like to show all 30 from S1 in the gridview with blank fields wherever V1 and C1 do not have data. From what I've read I need to do a left outer join. However, all examples I've found are with two datasets.
I've tried multiple times expanding on what I've found by changing it to a group join and also adding the .DefaultIfEmpty() property in the query, but nothing is working.
How can I change the above query to a left outer join with these multiple tables?
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Aug 19, 2010
I have two tabels as mentioned below. I am using entity framework and vs2010.I am not able to write linq query to get data from both the tables. there is one to many relationship(for one category ther can be multiple articles).
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Feb 18, 2011
I need to dynamically access some SQL tables hopefully using the Entity Framework. Here's some pseudo code:
var Account = DB.Accounts.SingleOrDefault(x => x.ID == 12345);
which will return me an Account object and this contains some fields called "PREFIX", "CAMPAIGN ID" and further information about the accounts are stored in separate SQL tables with the naming convention of PREFIX_CAMPAIGNID_MAIN.
The tables all have the same fields so I was thinking of creating a new Entity that isn't mapped anywhere and then dynamically loading it, like so:
var STA01_MAIN = new MyAccount(); // my "un-mapped" entity
DB.LoadTable('STA01_MAIN').LoadInto(STA01_MAIN);
I can now get anything about the STA01_MAIN account: STA01_MAIN.AccountId. So my question is: how do I access these tables using the Entity Framework?
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Jun 10, 2010
A relative newcomer to .net MVC2 and the entity framework, I am working on a project which requires a single web application, (C# .net 4), to connect to multiple different databases depending on the route of access, (ie subdomain).
No problem with this in principle and all the logic is written to transform the subdomain into an entity connection and pass this through to the Entity Model.
The problem comes with the fact that the different database whilst being largely similar in structure contain 3 or 4 unique tables bespoke to that instance.
To my mind there are two ways to solve this issue, neither of which i am sure will be possible.
1/ Use a separate entity model for each database. -Attempts down this route have through up conflicts where table/sp names are the same across differnt db's, or implicit conversion errors when I try and put the different models in different namespaces. or
2/ Overwrite the classes which refer to the changeable database objects based on the value of a base controller property.
My question is if either of theser routes can ever work in principle or if i should just give up on the EF and connect to the dtabases directlky using ADO. Perhaps there is another way to solve this problem i haven't thought of?
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Mar 17, 2010
I have created a .edmx for the northwind database. When I run the following statement, the correct number of detail records are retrieved and I can access the detail fields, but how do I access the order header record to view OrderDate, ShipAddress, etc...?
[Code]....
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May 3, 2010
I developed and entity framework (.edmx) application in 4.0 in that i got all the data of my querying table and its foreign key referenced tables data also. but when i change my project to 3.5 i am unable to get the data of foreign key referenced tables data.
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Jul 28, 2010
I am working with VS 2010, Entity framework, SQl-Server 2005, ASP.Net web forms. Currently, I am working on the Data access layer library which soon will be a web service, using Entity Framework collaboration with different design patterns like repository pattern and some best practices that posts in different blogs. I am also test each repository using the Unit testing project. Thumbs up! Working fine.
The thing I am worried about is, how much is good for retrieving data from a table that can contain 80-100k records ?
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Mar 21, 2011
Whats the best method to use with MVC? Entity Framework or LINQ to SQL?
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Aug 5, 2010
Im working on a greenfield project and have to make a decision on the technology we'll use for the data access layer. Ive used LINQ to SQL for a few years and am happy and comfortable with this, but now with entity framework available this is another method to consider. Are there any pitfalls using entity framework as opposed to LINQ to SQL ? Ive read that there are performance issues with entity framework, is this true? Id really like to get an overall feel for using one method over the other, anyone have any thoughts/comments/recomendations?
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Dec 15, 2010
I'm trying to learn MVC. Now I wonder whats the different between entity framework and LINQ TO SQL? Wich is the best to use and why?
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Dec 6, 2010
Im new to development for the windows server platform. Can someone tell me the difference between Linq to SQL and EF4?
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Jun 16, 2010
I am new to Entity Framework and working my way through it little by little. I think I have it figured out on how to get data into and out of 1 table at a time now the challenge is 2 tables into a gridview.
I have a user table that has a list of threads that a user can mark to track. Easy enough. Assign the userid number & threadid to a table with a push button while the user is logged in and viewing any of the posts that are on that thread. The new challange is to get only the posts that the user has marked to track. SQL easy. Entity not sure what to do.
If I make a view or stored procedure and add it to the database that would be an extra step. To join the 2 tables as in sql Select posts from posts where track.userid = @userid join track on post.userid=track.userid Seems Entity was made to avoid this type of thing. Than once the data is gathered I need to bind it to a gridview()
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Oct 11, 2010
what is diffrence between Entity Framework and LINQ to SQL i cant yet find a good blog on this i have read that in LINQ to SQL only one to one mapping is possible but Entity Framework allowes many , is it right? if so i dont understand this
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Oct 26, 2010
Could any one explain me which ORM is best?
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Oct 29, 2010
I have a new project where I want to use MVC (I will be learning as I code), and I have never used linq or entity (or mvc). Which should I use? Does it matter? I will be having a lot of different databases, from Oracle to FoxPro.
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