I am new to lightswitch as well as linq, i am using LS 2015. I want to know how to display the data of one table in other table's screen.
For example I have job vacancies, where I want to show candidate professional information who has applied for job. These two tables are related through Candidate personal ID, means a foreign key between candidate personal table and professional table.
The relation is as follows
JobVacancies->CandidatePersonalInfor->candidateProfessionalInfo. They are many to one related.
I have written a linq query to fetch data, where i have included some other tables also, my code is as follows
Any help is appreciated.
Have you defined the relationships you describe between the entities? If so, you'll have the ability to add and drop the details you require onto the form in the designer. The entities and their properties will be in the left pane of the screen designer.
If the join operation is more complex, you can use a WCF RIA Service to create a composite entity, as described in http://lightswitchhelpwebsite.com/Blog/tabid/61/EntryId/2226/Creating-a-WCF-RIA-Service-for-Visual-Studio-2013.aspx
Related
I'm developing a ADF Fusion Web Application and have some problems with EntityAssociations and ViewLinks.
I have a database table Project with id, name etc. Also I have a table Technology which only contains a id and the name of the technology, for example "ADF".
The relationship between theese two entities is many-to-many. Means one project can have multiple technologies assigned and inverse a technology can be assigned to multiple projects.
This relationship is described trough a join table named Project_Technology. Columns of this table are Project_FK, Technology_FK and Effort. Project_FK and Technology_FK are a composite primary key, Effort is an additional attribute.
Can someone explain me how to map EntityObject and ViewObjects that I can access the Effort, too? "Regular" many-to-many associations aren't that hard to implement but I am really struggling with the additional attribute.
Any help is appreciated. Thanks in advance!
Edit:
I could solve my issues. See answer below for details.
I got it working.
The Problem was the composite primary key on my join tables. It seems like ADF doesn't like them. I put a extra column ID on the join tables and now I can insert values by using the CreateInsert Data Controls.
I have a generic group members table with a GUID for a "group type" and a GUID for "referenced object". An example would be if I have a table of customers(each having a GUID) I can group them under "already paid" by creating a group GUID and in my "Group members table" referencing every customer by their respective GUID. This allows for any type of group to be added to the model as we expand(without adding extra tables).
Here is the problem. I have created a subquery in an entity in order to filter the universal group members table for a certain group and what "items" are and are not in that group; like so:
partial void ElementsNotMemberOfGroup_PreprocessQuery(int? UniversalGroupTypeIDParameter, int? UniversalGroupsIDParameter, ref IQueryable<UniversalGroupMember> query)
{
query = query.Where(x => x.UniversalGroup.UniversalGroupType.UniversalGroupTypeID == UniversalGroupTypeIDParameter);
query = query.Where(x => x.UniversalGroup.UniversalGroupsID != UniversalGroupsIDParameter);
}
This returns the GUIDs for the referenced object in the group, but for a user that's useless. I need to join this table and my customers table at runtime on the GUID so I can extract the customer info and display it.
Any Ideas?
LightSwitch wasn't really created with this kind of scenario in mind. LightSwitch makes things very easy for you when you create relationships between tables that are, well, "related". When you do this, you never need manual joins between entities.
While it's possible to do something similar to what you're describing (see the link below), it's a lot more work to achieve it, and in my opinion it isn't really worth the extra trouble. Not only that, but as you're discovering, it complicates even the most simple operations.
In essence, you're working against LightSwitch, instead of with it. My advice to you would be that if you really must do this type of manual optimization, then LightSwitch may not be the best product for you to use.
Beth Massi has a blog article, Using Different Edit Screens Based on Record Types (Table Inheritance), which isn't exactly what you're doing, but it may give you some ideas if you decide to still use LightSwitch for your project.
We use CRM 4.0 at our institution and have no plans to upgrade presently as we've spend the last year and a half customising and extending the CRM to work with our processes.
A tiny part of model is a simply hierarchy, we have a group of learning rooms that has a one-to-many relationship with another entity that describes the courses available for that learning room.
Another entity has a list of all potential and enrolled students who have expressed an interest in whichever course.
That bit's all straightforward and works pretty well and is modelled into 3 custom entities.
Now, we've got an Admin application that reads the rooms and then wants to show the courses for that room, but only where there are enrolled students.
In SQL this is simplified to:
SELECT DISTINCT r.CourseName, r.OtherInformation
FROM Rooms r
INNER JOIN Students S
ON S.CourseId = r.CourseId
WHERE r.RoomId = #RoomId
And this indeed is very close to the eventual SQL that CRM generates.
We use a Crm QueryEntity, a Filter and a LinkEntity to represent this same structure.
The problem now is that the CRM normalizes the a customize entity into a Base Table which has the standard CRM entity data that all share, and then an ExtensionBase Table which has our customisations. To Give a flattened access to this, it creates a view that merges both tables.
This view is what is used by the Generated SQL.
Now the base tables have indices but the view doesn't.
The problem we have is that all we want to do is return Courses where the inner join is satisfied, it's enough to prove there are entries and CRM makes it SELECT DISTINCT, so we only get one item back for Room.
At first this worked perfectly well, but now we have thousands of queries, it takes well over 30 seconds and of course causes a timeout in anything but SMS.
I'm given to believe that we can create and alter indices on tables in CRM and that's not considered to be an unsupported modification; but what about Views ?
I know that if we alter an entity then its views are recreated, which would of course make us redo our indices when this happens.
Is there any way to hint to CRM4.0 that we want a specific index in place ?
Another source recommends that where you get problems like this, then it's best to bring data closer together, but this isn't something I'd feel comfortable in trying to engineer into our solution.
I had considered putting a new entity in that only has RoomId, CourseId and Enrolment Count in to it, but that smacks of being incredibly hacky too; After all, an index would resolve the need to duplicate this data and have some kind of trigger that updates the data after every student operation.
Lastly, whilst I know we're stuck on CRM4 at the moment, is this the kind of thing that we could expect to have resolved in CRM2011 ? It would certainly add more weight to the upgrading this 5 year old product argument.
Since views are "dynamic" (conceptually, their contents are generated on-the-fly from the base tables every time they are used), they typically can't be indexed. However, SQL Server does support something called an "indexed view". You need to create a unique clustered index on the view, and the query analyzer should be able to use it to speed up your join.
Someone asked a similar question here and I see no conclusive answer. The cited concerns from Microsoft are Referential Integrity (a non-issue here) and Upgrade complications. You mention the unsupported option of adding the view and managing it over upgrades and entity changes. That is an option, as unsupported and hackish as it is, it should work.
FetchXml does have aggregation but the query execution plans still uses the views: here is the SQL generated from a simple select count from incident:
'select
top 5000 COUNT(*) as "rowcount"
, MAX("__AggLimitExceededFlag__") as "__AggregateLimitExceeded__" from (select top 50001 case when ROW_NUMBER() over(order by (SELECT 1)) > 50000 then 1 else 0 end as "__AggLimitExceededFlag__" from Incident as "incident0" ...
I dont see a supported solution for your problem.
If you are building an outside admin app and you are hosting CRM 4 on-premise you could go directly to the database for your query bypassing the CRM API. Not supported but would allow you to solve the problem.
I'm going to add this as a potential answer although I don't believe its a sustainable or indeed valid long-term solution.
After analysing the indexes that CRM had defined automatically, I realised that selecting more information in my query would be enough to fulfil the column requirements of an Index and now the query runs in less then a second.
I'm currently running in a multi-DB SQL Server environment and using linq to sql to perform queries.
I'm using the approach documented here to achieve cross DB joins:
http://www.enderminh.com/blog/archive/2009/04/25/2654.aspx
so basically:
2 data contexts - Users and Payments
Users.dbo.UserDetails {PK: UserId }
Payments.dbo.CurrentPaymentMethod { PK: UserId }
I drag the tables onto the DBML, and in the properties window, change the Source from dbo.UserDetails to Users.dbo.UserDetails to fully qualify the DB name.
I can then issue a single data context cross DB join by doing something like:
var results = (from user in datacontext.Table<UserDetail>()
join paymentmethod in dataContext.Table<CurrentPaymentMethod>() on user.UserId equals paymentmethod.UserId
... rest of query here ...);
Now this is tickety boo and works as I want it to. The only problem I'm currently having is when schema updates etc. happen (which is relatively frequent as we're in a significant dev phase).
(and finally, the question!)
What I want to achieve (and I've marked the question up as T4 as a guess, as I know that the DBML files are T4 guided) is an automated way when I drag any table onto a data context that the Source automatically picks up the DB name (so will have Users.dbo.UserDetails instead of just dbo.UserDetails)?
Thanks for any pointers :)
Terry
Have a look at the T4 Toolbox and the LinqToSql code generator it provides (Courtesy of Oleg Sych) - You can customize the templates to generate references however you'd like, but I think the problem you're going to run into is that the database name isn't stored in the dbml file.
What you could probably do is add a filter to the generator, perhaps using a dictionary or similar, such that in your .tt file, you maintain a list of tables and the databases they belong to. That way, if your maintenance task is to delete the class from the designer and drop it on again, it will get the right database name.
Have been trying out the new Dynamic Data site create tool that shipped with .NET 3.5. The tool uses LINQ Datasources to get the data from the database using a .dmbl context file for a reference. I am interseted in customizing a data grid but I need to show data from more than one table. Does anyone know how to do this using the LINQ Datasource object?
If the tables are connected by a foreign key, you can easily reference both tables as they will be joined by linq automatically (you can see easily if you look in your dbml and there is an arrow connecting the tables) - if not, see if you can add one.
To do that, you can just use something like this:
<%# Bind("unit1.unit_name") %>
Where in the table, 'unit' has a foreign key that references another table and you pull that 'unit's property of 'unit_name'
I hope that makes sense.
(EDIT misunderstood the question, revising my answer to the following)
Your LinqDataSource could point to a view, which allows you to overcome the problem of not being able to express a Join in the actual element. From "How to: Create LINQ to SQL Classes Mapped to Tables and Views (O/R Designer)":
The O/R Designer is a simple object relational mapper because it supports only 1:1 mapping relationships. In other words, an entity class can have only a 1:1 mapping relationship with a database table or view. Complex mapping, such as mapping an entity class to multiple tables, is not supported. However, you can map an entity class to a view that joins multiple related tables.
You cannot put more than one object/datasource on a datagrid. You will have to build a single ConceptObject that combines the exposed properties of the part Entities. Try to use DB -> L2S Entities -> ConceptObject. You must be very contrived if the DB model matches the ConceptObject field-for-field.
You are best using a ObjectDataSource when you wnt to do more complex Linq and bind your Grid to the ObjectDataSource.
You do however need to watch out for Anonymous types that could give you some trouble, but anything is posible...