Execute LINQ Query Using Properties Of Child Entity Set
Nov 25, 2010
I am having a meltdown over something that seems so simple and yet isn't working. Here's my scenario.
I have an object structure of tEvents, which contains properties of an event like a run of concerts. tEvents in turn contains an entity set of tEventOptions, which include properties like EventDate, Cancelled etc. I would like to query a list of tEvents using properties of the tEventOptions, for example filtering by date.
My pageis using a calendar object to show event dates. So I am trying to find if any tEvents in the List coming back from the database match the date of the day element being rendered in my Calendar control like so (in this snip 'data' is List and results from a db query):
[code]....
Except r, my query result var, is always true no matter what data it receives. I have tried the sub query using other properties of tEventOption and get the same 'true' result each time. I know that the data does not reflect this result so I clearly have a problem with the structure of my query, but for the life of me I cannot find a way to resolve it.
I'm building a music voting application, similar to stack overflow almost.I have 3 tables, Charts, ChartItems, Votes.I'm trying to bring back a list of chartitems, which link to a single chart, with the number of votes for each chart item counted.This is what I am trying currently
var firstList = from chartItem in db.ChartItems join vote in db.Votes on chartItem.ixChartId equals vote.ixChartId into j1 where chartItem.ixChartId == id[code]...
The problem is once I have performed the grouping, I can't get any of the other properties I need from the join to populate the model. For example each ChartItem should have a title, id etc...I have created a ViewModel to hold all the properties that I need, called ChartItemWithVotes(includes all entity values + int totalVotes)In the end I am looking for this
Hi guys I need to rewrite the sql query below using Linq to entity. Unfortunately I don't have a lot of experience of using Linq.
With TempTableName AS (SELECT [ColumnName], [ColumnName2], [ColumnName3], [ColumnName4], ROW_NUMBER() OVER (order by ColumnName desc) as RowNumber from TableName ) SELECT [ColumnName], [ColumnName2], [ColumnName3], [ColumnName4] FROM TempTableName WHERE ROWNUMBER Between 10 and 100
I am developing asp.net mobile application. I am using XML as a database. I am querying on the XML to access the required elements & attributes by using LINQ to XML in .net. I have the follwing part in my XML file.
[code]....
The similar logic I need for the above defined XML part. In the above XML I want to write the LINQ to XML query which can access the NAME attribute of the 'VALVE' node (<VALVE NAME="PWV">), then it should access the text between 'DISPLAY-NODE' (<DISPLAY-NAME> Production Master Valve </DISPLAY-NAME>), & then it should access the all the attributes of the 'COMMAND' node dynamically ( <COMMANDS USE-TEMPLATE="TRUE" TEAMPLATE-NAME="ValveCommands.xml"></COMMANDS>). All these I want dynamically without explicitly specifying the name of the child node as well as name of their attributes ( similar to the way I written the above query ) Can we write such a code by using LINQ to XML ? It will be better if we can write code for above issue in a single logic ( similar to the way I written the above query ).
I have a web app for our golf club. When I compute handicap index for each golfer, I have to select the most recent scores and then a subset of those scores depending on how many rounds of golf the golfer has played. All the scores are entered into a single SQL Express table called "Rounds". Verbally, this is what I'm trying to do:
1) select the twenty most recent golf scores (sort on date descending, "take(20)") [if less than 20 records, then select all available];
2) for this set of records, select the 10 lowest scores (or smaller number if golfer has less than 20 rounds);
3) compute the average round differential for the subset of records, etc. to calculate handicap index (this step is working ok...)
My current VB code has this LINQ query (which is flawed -- it selects the lowest handicap differential scores of ALL records for the filtered user):
[Code]....
How do I modify this query to accomplish items 1) & 2) above? It seems this should be simple, but my experience with queries is still limited.
I have added a partial class to one generated by the Entity Framework. I wanted to add a calculated field that I could bind to my GridView. However, when I try to access the new property, I get an error message that this is a limitation to Entity Framework.Are there any work arounds to accomplish this?
Need to figure out the correct way to do a simple SUM function in Linq, but also manipulate one of the feilds coming back by doing a Substring on it, here is the original SQL query:
I have this query for getting data through Entity Framework, which works today. Thing is, i want to create the query dynamically, i.e build it up in blocks, but i can't figure out how exactly to do it. I believe if i can somehow save one of the values that i retrieve in the beginning i can do it, but now i retrieve it twice (probably a bit slow as well? Unless the compiler fixes it before quering). Makes sense? Here is the LINQ:
Best way to show the SQL trace of a LINQ query to Entity Framework 3.5? I am using ASP.net and EF 3.5.
Dim dbo As Web.Portal.RBMEntities = New Web.Portal.RBMEntities Dim Query = From RoleAllocations In dbo.RoleAllocations Where RoleAllocations.user_id = _ID And RoleAllocations.expire_date > Today Select RoleAllocations
I am new to this, and I am trying to implement a linq query similar to db.Genres.Include("Albums") command from
mvc music store using my current DB setup. I realize that the tutorial mentions Checlking the "Include foreign key columns in the method" when creating the tables in ADO.NET, but if I am using LINQ to SQL classes, then how can I obtain the same effect. And how do I use db.Genres.Include("Albums") to simplify my life?
But child-action can not return a redirect-action-result, because this code is excuted when server is rendering HTML to client.
Now, I want to invoke an action by code in Controller, it returns an ActionResult. Then, if it's a redirect-result, I returns it. Otherwise, in Razor code, I renders this ActionResult. For example:
I have been listening volumes about this entity framework and though to have a dive in it. I got 3 tables and got the entities and model setup for my database, upto the point where I tried to execute sproc with the datacontext class. I added the sproc to Function Import but as Function Import does not support returning custom dataset that m sproc generates. I googled and found to create Complex Type, but here is the problem, "Get Column Information" in Add Function Import is disabled for me . why the heck its disabled, how to make this work and don't want to revert to older approach just that I could not execute sproc with EF.
Within my project I have created an Entity Data Model, complete with relationship links between the various tables. I notice when I do so, Visual Studio automatically creates a property named after this link.
I have then generated a Domain Service Class based on this data model, and once again within this a property is generated representing the link, ie within my ChemicalApplication class there is a Chemical property of type Chemical.
The trouble is, within the silverlight client, I can access the ChemicalApplication data object no bother, and can see the ChemicalApplication.Chemical property, but as soon as I try to access it, I recieve an error that the property is not initialised.
Do these auto-generated child properties not automatically initialise? If not, how do i manually assign a value to them within the RIA Domain Service?
Dim MediaQuery = From m In dB.DOWNLOADS _Where m.ID = id _Select
which returns a record from the database. One of the fields in the record is a FK to another table. I need to read this value to be able to set a dropdown based on the ID but I can't work out how to access it. For a standard record I can just do the following txtTitle.Text = MediaQuery.FirstOrDefault().TITLE
However with the foreign key it doesn't work like that. I've tried drpGroup.SelectedIndex = MediaQuery.FirstOrDefault().DOWNLOAD_GROUPS.ID where DOWNLOAD_GROUPS is the FK field but it returns Object reference not set to an instance of an object. If you're simply wanting to read some values from a single db record in the entitiy framework and one is a foreign key how should I go about getting the value?
string strCondition = "FirstName=='abc'" from p in People.Where(strCondition) select p
In our architecture we are usign both Linq-Sql as well Linq-Entity. So please give some thoughts wehter it is possible or not and is there any way to perform this?
I've been learning MVC 2 and I have pretty much everything understood except for the model part of things, I understand what the model is but actually implementing it has me confused.
Here's my situation, I have my DB which has 3 tables;
Ideas - table of ideas Tags - table of tags IdeaTag - link table connecting the above 2 tables via FKs
So when using the Entity Framework (.edmx) designer in VS2010 I get 2 classes created in the Designer, which obviously map to my DB tables and Navigation Properties in Idea for Tags & Idea for Tag.
So this is all fine until I actually try to add tags to an idea, what's the best practise for dealing with Navigation Properties? I wanted to add a Textbox which will then map to the Tags property in the Idea class but I'm unsure how I'd go about this.
Most of the MVC tutorials which discuss EF or Linq to SQL are quite basic.
EF is so frustrating. I can't seem to be able to get my head around what I need to do so I can delete an object. I seem to be able to remove the object but not the related child objects. Can anyone tell me what is the rule of thumb when you want to delete all related child objects of a given object? I've tried loading all related objects like this:
Entry entry = ModelContext.GetObjectByKey(new EntityKey("ModelContainer.EntrySet", "Id", id)) as Entry; entry.ChildEnteries.Load(); if (entry != null) { ModelContext.DeleteObject(entry); ModelContext.SaveChanges(); }
I get errors related to the relationships: A relationship is being added or deleted from an AssociationSet 'EntryEntry'. With cardinality constraints, a corresponding 'Entry1' must also be added or deleted. Why can't I just load the object using modelcontext.GetObjectByKey and remove it along with its child objects? My other question is can I delete an object using Entity command like so? DELETE e from objectset as e where e.id = 1 I've tried few variations and all of them throw exceptions.
I'm embarrassed to ask this here because it's clearly been duplicated several times already on StackOverflow. I've read a lot of stuff including:
[URL]
I think I've done exactly what those article say, but it's not working for me.
Here's the top of my master page, named "MasterNoNews.master":
[code]....
In the first case, VS is telling me System.Web.Ui.MasterPage does not contain a definition for urrentUser. In the second case, VS says the type or namespace 'MasterNoNews' could not be found.
I've got a composite control (class) that exposes an asp:Label through a get-property. Is is possible to set the Text property of the Label through aspx-code?
I'd like to do something like this: <cfw:MyCompositeControl runat="server" Label.Text="Test" />
One solution is adding each property to the composite class (like a public LabelText), but I'd like to set any property of any child control. So as new features of child controls become available, I'd like to be able to use them on my composite control. So basically I would like to set any property of the exposed child control.
